Just a few notes from an outside engineer's perspective.

First, I would recommend having the "Shift Adapts" reset for the Transmission Tune.
Anytime that one of these cars was driven with a slipping transmission, the control module raises the line pressure and shift timing to try and prolong transmission operation.

Now the transmission has been replaced, and the control module will not have a way to go back to setting normal line pressure and shift timing until the vehicle has been driven for a prolonged period of time, and the control module has recorded reoccurring healthy transmission behavior.

So instead, you can manually have the "Shift Adapts" reset for the Transmission to stop the current behavior, and start observing the new transmission, then return to normal behavior right away.

Otherwise the control module is remembering the old slipping transmission's behaviors.

Next, if you still have some banging and clunking under the vehicle; part of what you are describing sounds like either a bad transmission mount, engine mount or loose fastener pertaining to either.

I am referring to banging/ clunking like the drive-shaft fell out/ rocking the driver's seat.

There is more that I could post regarding the Cooler possibly not being flushed and the Repair/ Business that you used, adding chemicals to the transmission fluid without speaking to the transmission builder, but I am not getting into that.

After listening to you, I feel like you really would have possibly been better off with an upgraded but stock performing transmission and torque-converter.
Not a higher stall speed torque-converter and high performance transmission.

Lastly, I do not really know Frank well, however everything that I have seen him post about has been in my eyes, beneficial improvements to the components and designs for the transmissions that he is offering.
I really have not seen anything that could actually be viewed as undesirable.

Best of luck to you in your situation,

-Chello III

 

I agree with you, however I do feel that many inexpensive torque-converters (usually those like B&M and TCI were notorious for) can feel relatively loose to someone that has only been accustomed to a stock stall speed torque-converter.

Only from reading Frank's posts, I would like to believe (although I loath to assume) that the OP is referring to modifications that Frank makes to the TCC Regulation Valve-Train for lock-up pressure/ feel.


--Chello III

 

Its not PWM mod it is the full time overun mod . Keeps the overun clutch on in D4 3-2-1 this causes a downshift bump 3-2 as you are coasting to a stop . It should not affect upshifts however, But indeed it does have a shift kits set up for firmer shifts across the board . Though at least on my PC it hard to read i think he is just speaking of the downshift .

 

A 3200 stall is a considerable increase over stock. My 2800 with 3.08 gears also an FTI but billet triple disc will pull the car a little at idle cold as it at 1200 rpm but does not when at hot idle 750 rpm at all .

A kick down with a 3200 stall is going to hit had particular at lower speeds like 40 mph , Mine drops to 1st at that and turns the wheels loose and shifts pretty aggressive into second. Though mine is a stage 3 and yours a stage 1 the shift kit is identical except instead off ,083 second feed with the sonnax 2nd , You would have the .093 feed with the corvette servo .

The downshift clunk and the very light throttle clucky feel up and down is a result of the overun mod, Bear in mind with the stock set up the sprag would be freewheeling in this situation. so you would feel little to nothing,

If your drive has much incline at all with the 320o depending on your rear ration which I do not know it might take much more throtlte to get going that you were used to with the stock converter.

Obviously I cannot feel the trans to say what is normal or not, But overall shifts are not going to feel like stock . And driving normally because of the higher accelerating you are giving more throttle and will see higher line and formed shift feel than stock..

Some notes also - A tune may be required if you have issue with limp mod with the 3200 stall which can happen low numerable ratio you have the more likely this is to happen.(3rd gear start no shifts ) SHIFT SOLENOID B CODE.

Drivability will likely improve as the PCM learns , The clunky intermittent feel will likely stay as part of the overrun mod and varies to each vehicle .

A tune can certainly improve drivability and performance .

It does have a .500 boost valve and spring mod so overall line is going to be higher and shift feel firmer , And coming from a stock trans and converter might be a learning curve of the feel pf the trans.

As stated if it has a stock tune it may take some time to adapt , Resetting wont really help as far as a the shift feel and might even make worse though I do not not thing you can reset adaptive outside of actual tune with something like HP TUNERS.

I must however say I am a bit disheartened as all units i have built since I started this in 2022 have the same shift kits with only variations for application such as HD verse performance builds and till now I have not had anyone unhappy with the overall shift feel . But maybe as you drive and get more accustomed. I know in my own car going to the 2800 stall from stock was a bit of a learning curve as I learned that unlike the stock converter where you gently throttle and take off , I was much better off getting on it and just get going as it feel way draw out and yuky ay very light throttle . My cars stock converter was 1400 rpm and with 3.08 gears it was a pretty drastic change for me though I feel in love he first I LAID INTO IT .

I will conclude though it will never feel like stock nor have the same drivability feel as stock as that is not what it was built to feel like.

If you have any concerns always feel free to contact me any time as you know I am always available.

 

This is honestly shocking to me.

The majority of my experience is with Yank and PI units with stall speeds of 3200 to 4000 rpm in 4L60E F-bodies with both 2.73 and 3.23 gears. Even at stock idle rpms of 550 in gear, I have never experienced one of these converters NOT pulling the car forward in gear at idle on level ground. Even the cheaper B&M unit in my TH350 '71 will do this at low idle speeds of <700. I've never driven any car with a rated stall speed of ~3000 rpm that wouldn't at least creep forward in gear at idle.

Thanks for the clarification on the "PWM mod" actually being an overrun mod. That makes much more sense now.

 

Like I said even with my own car, 2800 with 3.08 it depends on idle speed. At 1200 cold oh yes it creeps and actually I find it a little annoying and can't wait till it warms up.But when warm and the idle drops down to 750 , Yes you can feel it go into gear lightly, But on flat ground it just sits there. Now throttle it up near 1000 it starts moving , I will say at least in my own car the flash for the stall is pretty much right on any hit an you are right to about 3000 rpm and gone. Even cruising along at 40 mph in 3rd (I have my part throttle shift points raised as I didn't care for the slippy feel with the slippy feel with stock shift points( But a kick down will light the big iMPALA posi tires right up P275 40 R17 but prior to the 2800 it does feel pretty loose . Of course converters vary things like STR and such can drastically change the behaviour of one converter over another even at the same stall. Mine I had never had a true high stall in a car prior to this. My buddy did have a vega converter in a 350 years and years ago, It was horrid driveability wise but fun when you hit it. but even the 2800 was a bit of a learning curve as far as driving around town in traffic. I learned quicker launches feel much better than the old gradually accelerating. Before I raised the part throttle shift points I hated the way it felt shifting up into 4th by 35 to 40 mph around town felt very loose. but once I raised the PT shift points that was fixed and the rest I learned and adapted too.
As for the Overun mod and the clunky on slow moving and coast feel at low speeds.
With my car it is most notable early part of drive while in cold mode .I noted it is more notable and i data logged indeed the line is higher as its commanded to be looking at EPC current I assume due to higher idle speed and much less so when warm. I did lower my coast down 3-2 to like 2 mph. But Others like one customer actually raised it as he liked the more pronounced down shift that felt more like if you manually downshifted. (Preferences) I guess.
As for the feel of the OP car I cannot say what is normal as I cannot drive it, It will never feel stock coming from stock only a person with a similar set up who is used to driving one could make that determination. But to me sounds mostly like just not being used to a performance trans with a shift kit - overun mod - stall . The Overun mod while it does have some drivability glitches by nature and probably why GM didn't do it even in D3 though it appears the VB was originally designed to do it. But I started doing it over a decade ago and from that point forward not a single rolled or broken input sprag at any power level.

Also a note , ADAPTIVES with a higher stall left functional they themselves may raise the line and make the car shift firmer than expected and minus any true INPUT SPEED other than ENGINE RPM it may make the **** time seem excessive and cause line to rise to compensate. I actually turned my off as I found it was indeed raising line at low speeds and lowering at WOT I would make changes to pressures to get some particular feel and get exactly what I wanted only to have it soften back up after a couple days (This was heavier throttle shifts I want firmer. And found it was another table working hard against me tryin to get that .250 sec shift time my factory tune was set at. I found the table and changed it to 0.00 and it stopped doing that.

Sorry for long rant I tend to over talk lol

 

My very first aftermarket converter in a 4L60E was a Yank SY3500. This was a soft hit (1.6x STR) unit. It pulled the car ('00 Trans Am, 3.23 gears) forward at stock 550rpm idle speed no problem. I had that same experience with other Yank and PI converters of ~3k to 4k rpm stall speeds and STRs in the ~2.0 range. They didn't pull forward quite as strong as a tight stock converter, but they definitely pulled forward even at low stock idle rpms.

Never had an FTI brand converter personally, but I'm shocked that no forward movement on level ground at idle would be normal for those at 3200 stall speed in this application.

 

Sonnax:

"Another very important concern with the TAPS is to always reset them after any major transmission/ transaxle repair work has been done.
If you have a PCM that has been adapting to long shifts from a burned clutch, burned band or an internal leak, it has compensated by raising the TAP psi.
If you don’t reset the TAP after you make the repair, expect a harsh shift.
Not knowing this and failing to reset the TAPS may lead you to unnecessary work such as chasing down a harsh shift after a well executed repair.
The system will adapt to the repaired operation of the unit over time, but this can take many drive cycles.
The desired adapt value after a repair will most likely be far closer to the zero point than the pre-repaired value that had adapted to a problem.
You will get to the new value more quickly if you reset, and at the same time you will avoid “building in” a temporary new condition such as a harsh shift.
The fastest way to reset the TAPS is with a scanner.
However, not all scanners have the reset feature.
If your scanner doesn’t have the reset ability you can try disconnecting the battery for a long period of time. (Usually it takes more than 30 minutes.)"

Full article in hyperlink below:
Transmission Adaptive Pressure Shift

I also have articles by GM if preferred.

No tuning required, just a reset via a scan-tool from most any service and repair business.
There is nothing to turn on or off like the "Torque Management" sub-system.

Obviously there can always be manual tuning of the parameters pertaining to Torque Management or Adaptive Shift Pressures via aftermarket software.

 

When I had the transmission installed I brought the shop Valvoline Maxlife ATF to use which has about the same Viscosity index as Valvoline’s Dex VII. Their Dex VII is rated at 6.0 cSt at 100*C and their Maxlife is a little thinner at 5.9. Dexron III was/is a little thicker than Dex VII (it was rated in the 7’s at 100*C vs Dex VII’s 6’s) so I thought I would see if a little thicker fluid would help. This past weekend I did three drain and fills with Valvoline Dex/Merc which has a viscosity rating of 7.1 at 100*C. I was only able to get about gallon of fluid out each time so I suppose there’s a little bit of the thinner “Maxlife” ATF left in there. I only have about 20-30 miles on the new slightly ticker fluid but it will almost pull itself on level ground now. It’ll inch forward a little anyway. It also seems to be shifting a little smoother and it has only “clunked” on a slow speed 2nd to 3rd shift a time or two. It didnt feel it in the seat when it clunked this time I could just hear it, so that’s an improvement I guess. I have a little over 200 miles on the trans & converter now. Redline brand has an ATF that they say is speced for Dex III but it’s a bit thicker. It’s rated at 9.5 cSt at 100c* vs 7’s for “normal” Dex III. For something to compare it to it’s like a 5w30 vs a 5w20. I’m thinking about using a couple quarts of it (maybe 4) when I change the filter at 500 miles. Maybe the thicker fluid will band-aid it some more. If it’s mixed with Valvoline Dex/Merc the viscosity would be an 8 some odd at 100*C so I don’t think it’d be too thick.
The take away I guess is that it shifts a little better with Dex III than VII and that if anyone is looking for a little higher stall speed maybe try Maxlife ATF.

 

Interesting , Though I imagine part of what's improving has to do with the learning function of the PCM also. But indeed a thicker fluid would/could yield a different feel and stall .
Note the 500 miles is just an arbitrary number I chose for the first filter change . So assuming you changed it something over 100 miles , You do not have to change it at any but normal periods I do mine like every 3-4 oil change.
Keep me posted as you are to date the only person who was uncomfortable with the shift feel. So I am somewhat perplexed. Usually the only complaint i get is the 3-2 downshift with the overun mod on some cars (depending on car-rear-converter-tune) it can vary from mild to abrupt.)
Anyway glad seems somewhat better now .
Holler if you need anything.

 

You seriously should have the Transmission Mount and the Engine Mounts inspected and/ or have the Shift Adapts reset.
Doing nothing is not a solution.

I have no doubt in my mind that Frank's Custom Transmission has built a great 4L60E, as he has done so many times before.

There is something else going on here, as your experience in your Post does not coincide with what everyone else here has experienced with Frank.

 

I definitely agree that something somewhere still isn't quite right. I just have a hard time believing that the normal standard for an FTI converter in this application, at that stall speed, is no forward movement (behaving as though it's in neutral) at idle in gear. I have never experienced this with any brand of converter in any 4L60E LS1 F-body at any stall speed of ~4k rpm or less.

Have you contacted FTI about this? Just curious about their thoughts on a potential cause, and/or if this is normal for their particular brand of converter.

As it was a 3rd party shop that did the install here, I just wonder if something didn't get damaged during the process which might be leading to some of the odd behavior.

 

The transmission mount is a new rubber mount and the motor mounts are OEM. That being said, the old transmission never “clunked.” The shift from first to second was starting to get long (slip) so I decided to rebuild vs replace.
I reached out to him after I got it home from being installed. Frank told me that a clunk when coasting to a stop was a normal function of the PWM mod, and that the trans was built for performance and not comfort. I understood that to some degree going into it because I realize that there’s always a trade-off with “hot-rodding.” But in my head I was thinking that the “discomfort” would occur at WOT and not light throttle stop light to stop light. Especially not a Stage 1 😂
I did my homework after it was installed and it looks like slow speed “clunks” etc are a pseudo common trend with 4l60e’s with “shift kits,” and most try to address the issues via tuning. Live and learn I guess.
WOT pulls from a 10-20’ish mph rolls are pretty fun now. It’ll spin the tires and the rear end will wiggle some. I forgot to turn traction control off both times I did it but I just kept my foot down and powered through it. At any rate, WOT shifts are good. They’re quick and silent. There’s no noise other than the tires and the motor. I can’t feel it in the seat either when it shifts at redline. Since there’s no clunk at 6k rpm but there is when it shifts at 1,500 I think we can rule out the mounts. The Dex III has made an improvement over the Dex VII and I’ve only driven it 20-30 miles with the III, so maybe there’s more improvement to come. I think though some of the “slow speed discomfort” (if not all) is the nature of the beast. You know, in order to make it stronger one must remove/modify X which “job” was to “provide comfort.”
200 mile summary- WOT pulls equate to a grin. 15-20 mph into 3rd at 1,500 now and again make me cringe. I haven’t noticed it clunk from 3-2 when coasting to a stop in awhile. I bet most of the people who have used Frank’s or any other custom tranny and higher stall in the modern age have tuning capabilities so they can play with “work arounds.” That might be why I’m the only “complainer.” I think my “work-around” will be slightly thicker fluid. 😁 I also might be the only complainer because maybe everyone else is using them in drag cars and not street cruisers. Who knows.

I don’t think he’s going to lose any business. You can relax a little.
Here’s something I’ve been pondering on. So you know how everything is a trade-off? Hard shifts are said to be better on the clutches, but how are the hard shifts on the driveline? Are you sacrificing driveline component life for transmission clutch life with hard shifts?

 

I had a couple "built" 4L60Es long before tuning (beyond simple shift point changes, etc.) was a commonplace thing for these transmissions. We're talking 25 years ago. I didn't have any issues with harsh slow speed up or downshifts with mine, but I don't think my units had any sort of overrun mod performed. I don't think you're actually referring to a PWM to vacuum modulator mod in this case (I did have that modification, and it caused no such issues at slow speeds, but did occasionally shift a bit hard going into gear from P/N). I think there is some confusion here about the overrun mod vs. PWM to vacuum.

 

When I was googling PWM mods I think I ran across one of Frank’s post on an Impala formum saying that he uses a “heavy spring” for his PWM mod. I’m not sure if it was THE Frank, but it was a Frank.
*Edit* Yeah it might have been the overrun mod. None the less it clunks time to time when you’re moving slow, and I think “a heavy spring” might be the culprit.
*Edit* Yeah it has a “full time overrun mod.” I guess that’s the clunkster.

 

This makes more sense. PWM = Pulse Width Modulation, which was the OEM setup for your trans. It used to be common for 4L60E builders to convert to vacuum modulation as part of their HD 4L60E builds, but that alone would not cause what you are describing. Overrun mod is something different.

Something I posted earlier but that may have been missed as it was posted almost immediately before one of your posts:

I definitely agree that something somewhere still isn't quite right. I just have a hard time believing that the normal standard for an FTI converter in this application, at that stall speed, is no forward movement (behaving as though it's in neutral) at idle in gear. I have never experienced this with any brand of converter in any 4L60E LS1 F-body at any stall speed of ~4k rpm or less.

Have you contacted FTI about this? Just curious about their thoughts on a potential cause, and/or if this is normal for their particular brand of converter.

As it was a 3rd party shop that did the install here, I just wonder if something didn't get damaged during the process which might be leading to some of the odd behavior.

 

I haven’t reached out to FTI but I believe that I may to see what they say. You’re right it could be an install error. The guy that put it in messed up the tail shaft seal install (I think he messed up the housing removing the seal) so it’s possible that he didn’t get something else correct. I don’t know anything about auto transmissions but I’m assuming the only thing to mess up on a torque converter install would be the spacing where it bolts up. Slightly thicker fluid “tightened it up” some for whatever that is worth.
FTI 3200

 

@Y2K_Frenzy

The OVERUN mod is the source of the low RPM clunky feel of up and down . As factory instead over overunning it would have freewheeled like a 10 speed bike when you stop pedaling just coast so no tight abrupt feeling up or down clunk. the overun mod at least mine mine and anothers a relatively new mod (STARTED ABOUT 10 YEARS AGO) but changed the 60E in my builds and others dramatically rasing power handling of the unit. But as you mention every pro always has a con usually a trade off for comfort.
This clunk is why GM disabled Overrun EVEN IN D3 second gear and if you look at tune have negative numbers in the pressure table during these conditions.
As for the pulling or lack of rather and based on the fluid viscosity affecting it I would say its just the converter on the looser side. I know my own car with 3.08 and a 2800 will either sit or barley creep at idle 650 to 700 rpm hot)
Now what can I offer ?
1-If you pay shipping I will build you a stockish but well built 4l60e without the overun mod and we can swap
2- optionally since the OR MOD is reversable easily I will send you another VB and Plate which is not as performance oriented which will also solve the clunk 2-3 3-2 issues and pay up to 200 dollars for someone to do the VB swap (Note this will also return trans to close to stock power handling as much of the ability comes from the shift kit mods. So rating will drop to near stock which most agree is under 400 rwhp. However with either scenario I will still warranty for the term agreed as I have posted.
These are two options I can offer you if you find that the feel of it is intolerable to you.
The creep pull at idle I can do nothing t change but If you contact FTI I do think they offer a restall.
The more I read the more I think what we have is a case of a performance trans with the expected feel of a stock unit. As you mention all is a trade off when it comes to all areas of performance. Engine, rear end, trans everything trades something for something else. Example my car has 3.08 gears and runs good but 373 would perform much better being quicker at a trade of 1/2 the fuel efficiency on the hwy. The 2800 stall means more throttle to get going and converter slip at low speeds around town but I get in return the ability to turn the wheels loose at 30mph on a kickdown.
The overun mod makes sure I will never see a broken or rolled sprag from that kickdown , But the trade off is a clunky 3-2 downshift and a different than stock low speed clunky feel on upshift.

As for the feels of the performance units. All units share the same shift kit , With the stage 1 and 2 feeling the same and the stage 3 and max being much less comfort wise due to the much larger 2nd servo and 2-3 accumulation limitation it causes.

Anyway as I have stated before, if they is anything I can do to help including the options listed above please let me know and we will get started making them happen.

Also to clear this up , its is the Overun mod , if At some point some place I typed PWM mod it was a mistype. PWM only has to do with lockup and nothing to do with how the trans shifts or feels outside of that..

As to instal error I do not think the install has any bearing on the feel of the trans though the seal installation in your original tail as I do not send those is their issue and the potential not having flush the cooler. But I think its is just a case of expectation of a performance trans / converter not feeling or acting like a stock unit / build would.

Thanks Frank

 

I agree with everything Frank said above regarding the trans itself, but I still think that something isn't quite right with the converter behavior (not necessarily FTI's fault either, perhaps the converter was mishandled during install, etc.). This part is telling:

In a 4L60E, the internal first gear ratio is 3.06:1. Reverse is 2.29:1. If it pulls fine in reverse, I can't see any reason why it wouldn't pull forward just as well (or better, based on gear ratio) at the same idle speed and level ground.

I'd reach out to FTI and explain all of this, see what they say. 3200 stall speed is not that loose, IMO. I've experienced a wide range of STRs at stall speeds of 3500-4000+ in 4L60E F-bodies with 3.23 gears, and none of them have behaved as though they were in neutral (when in gear) even at stock idle speeds on level ground. Granted, as stated above, I've never had an FTI converter but I'd be surprised if this is "normal" behavior for the unit. Again, not pointing any fingers at FTI here as it's entirely possible that something wasn't perfect with the install (converter seating, etc.), especially since it sounds like the installer messed up on some other items per your post above. Perhaps the shop even "fixed" their mistake but some amount of damage was already done. Just speculating here, as I feel that something isn't quite right with the idle behavior you're describing for the application.

 

I all so agree that OP seem to be expecting a performance trans to act like a stock one. Frank has stated numerus times in different threads that the overrun mod has a clucky feel.

This is stand up of Frank to reach out to the OP and offer options to try to make him happy with his trans.