Conversions & Swaps LSX Engines in Non-LSX Vehicles
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'70 Nova LY6/TH400 6.0VVT

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Old 04-04-2017, 01:12 PM
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Thank you Jimbo. I lost my grandfather. He had leukemia which started a little over a year ago and his chemo eventually stopped working. We grew closer and I am grateful we had that time. Before he died, I conducted a few interview sessions on camera and captured some great stories about his life. He was a depression era kid who immigrated from Missouri to California and started in migrant farm labor. He eventually became a fireman and worked his way up to battalion chief before retiring early and spending nearly four decades serving his church alongside the love of his life, my grandmother, who died a few years before him. I miss him dearly, although he was ready to go be with her and he was lucky to pass without great pain and absolutely no regrets.

Regarding the car, the transgo kit is expected today. I am not feeling confident it's going to solve the issue since it doesn't change/replace the 2-3 or 3-2 valves or springs, although it will change the line, governor, and modulator pressures that operate them. I intend to disassemble, inspect and clean every valve in the valvebody and perhaps I will discover what's wrong in that process. Plus replacing the vacuum modulator and installing the transgo spring behind the modulator valve could have an effect. Somewhere in these parts I may just end up with a better performing transmission.
Old 04-04-2017, 06:38 PM
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At first glance, it seems that something is amiss in your 2-3 valve, governor, and/or vacuum modulator. The 2-3 valve is held in the downshift position until governor pressure overcomes modulator + spring + detent pressure.

However, since you mentioned that it was running fine pre-swap, maybe it's the kickdown (detent) solenoid. You mentioned that it is completetly disconnected - why? Improper kickdown could cause your symptoms, with the governor circuit fighting the detent + modulator circuits. The fact that it won't shift above 2nd with the modulator disconnected seems to suggest this, as the mod and detents are on one side of the 2-3 valve, while the governor is on the other. Further, the mod pressure increases with engine load (i.e., inverse of engine vacuum), maxing out under WOT (zero vacuum).

It's also possible that your boost valve (or any valve, for that matter) is worn, but I don't think that's the cause because, again, you said it was working fine prior to the swap.

Here's a good TH400 explainer.

Edit: Just saw that you got a switch for the kickdown. It might be prudent to reassemble the trans and try the switch before you go drilling and modifying things.
Old 04-04-2017, 07:03 PM
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I wouldn't say it was working "fine" prior to the swap because it never shifted 2-3 under WOT, however it did not have the issues of (1) shuttling back and forth between 2nd and 3rd gear or (2) downshifting from 3rd to 2nd when throttle was applied.

I have no good reason for not having a kickdown switch installed/connected, but it was not installed on the old engine either and I was able to drive around without issues I'm having currently. The detent solenoid has always been in place inside the transmission and from what I saw it looks to be in good shape. I do not think the detent circuit is active because the 1-2 shift is still happening at very low speeds and the shifts are all soft; if the detent were active, the 1-2 shift point would be raised and the shifts would be firm.

The 2-3 valve or the 3-2 valve seem like the most likely culprits here since they both affect shifting to and staying in 3rd. It's also possible the governor is never developing enough pressure to adequately affect and hold the 2-3 shift without a significant reduction in modulator pressure (via vacuum modulator), but I don't think the governor itself is the issue.

Heck I really don't know - I just hope this shotgun approach works. Thanks for weighing in and offering some ideas too!
Old 04-05-2017, 01:04 AM
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2-3 / 3-2 valve(s) or line pressure, based on your 1-2 shift firmness, or lack thereof.

I just poured through the build to no avail trying to find your "it worked fine prior to the swap" line, and I saw that I never answered your Procar question. I had the Pro 90 high-backs, which my friend sold me after ripping them out of his 68 Camaro. I made custom brackets and my head still touched the headliner. I've heard good things about the Rallys, but I can only hope they sit lower. That said, I can't say enough about the Corbeau GTS II's I have.
Old 04-05-2017, 10:17 AM
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Originally Posted by hookemdevils22
I just poured through the build to no avail trying to find your "it worked fine prior to the swap" line
It's probably in there somewhere. I had forgotten about the issue with not shifting to 3rd under WOT - it's just something I've lived with over the years and never really put much thought into. I would let off momentarily and it would shift into 3rd then hold it just fine when I got back into the throttle. That's no longer the case since doing the swap; now it doesn't want to hold 3rd unless the speed and part throttle conditions are just right.

Originally Posted by hookemdevils22
I saw that I never answered your Procar question. I had the Pro 90 high-backs, which my friend sold me after ripping them out of his 68 Camaro. I made custom brackets and my head still touched the headliner. I've heard good things about the Rallys, but I can only hope they sit lower. That said, I can't say enough about the Corbeau GTS II's I have.
Thanks for responding. I think I've narrowed down to the Rally seats primarily for the vintage look, but I have yet to sit in them and I'm still concerned about height. It's nice that Corbeau gave the option to shave the base - I'm sure your seats sit a lot lower than most. Mine are currently sky high but I can live with that for a while.
Old 04-05-2017, 11:11 AM
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My Summit order came in yesterday. Transgo 400-Pro shift reprogramming kit, filter, rubber pan gasket, modulator, and a nitrous WOT switch I plan to use for kickdown.



I had time to get started on the install. First step was swapping the pressure regulator spring to up the line pressure a tad. The pressure regulator is under the snap ring near the top right of the photo below - you have to press and compress the spring while removing the snap ring, then the components will come out. It's tough to do - there's not much space for maneuvering snap ring pliers and a long screwdriver to push things in.





Above is the pressure regulator / boost valve assembly removed. The yellow spring and a couple of horseshoe spacers are what I found in my transmission. The Transgo kit comes with a stiffer orange spring which I installed without any of the horseshoe spacers.

Next the kit has you replace the 1-2 shift valve with a manual version. My valvebody already had one, but I decided to exchange it for the Transgo version. In the photo below, the Transgo 1-2 valve is the one inline with the assembly and the one off to the side is the old one. I noticed one of the lands on the Transgo valve is shorter than the old one. I don't know what difference this makes.





The last thing I had time for was the front 2-3 accumulator. I discovered the old one was locked down against the valve body with a pair of nuts used as spacers. From what I understand, this little modification makes the 2-3 shift much firmer since the servo moves freely/quickly without any interaction with the accumulator. However since I am trying to return things to a known state, I've decided to undo that modification and install the Transgo accumulator piston spring and allow the piston to move again.



Transgo included a new piston in their kit (left in the image below), but the hole in the center was undersized and it fit too tightly on the shaft they provided. So I reused the old piston I had and added the Transgo spring and shaft.



Something bothering me is that when I tilt the valve body side-to-side I can hear something clicking back and forth like if a valve were sliding from one end of a bore to the other. I'm not sure where it's coming from but I intend to find out, because I thought all the valves in this thing were spring loaded and should not be floating around loose.

That's as far as I got for now.
Old 04-05-2017, 04:44 PM
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I spent some time on the phone with Transgo tech support - very impressed with how much help they were. I gave them some backstory on my 2-3 shifting problems and they suspect either 2-3 valve or a problem with one of the internal seals. For the 2-3 valve, they gave me some spring specs so I can check spring forces. For the internal seal issue, they outlined a process for using compressed air to check if the internal seal is working. He said the transmission may be trying to apply 3rd gear earlier than I think, but unable to hold it due to insufficient pressure on the controlling circuit. Unfortunately a lot of the conversation was above my technical competency. They also told me to get a new detent solenoid even if mine looks fine, so I will do that. They weren't particularly hot on using the orange pressure regulator spring for my application, but thought it was a better idea than using the yellow spring of unknown origin. I should have asked what pressure they expect with this setup.

I also told them about the sound of something clicking back and forth when I tilt the valvebody and they said that is probably the spacer pin in the 3-2 shift valve. It floats inside the spring and that's normal.

Last edited by -TheBandit-; 04-05-2017 at 04:49 PM.
Old 04-05-2017, 06:52 PM
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Originally Posted by -TheBandit-
I spent some time on the phone with Transgo tech support - very impressed with how much help they were. I gave them some backstory on my 2-3 shifting problems and they suspect either 2-3 valve or a problem with one of the internal seals. For the 2-3 valve, they gave me some spring specs so I can check spring forces. For the internal seal issue, they outlined a process for using compressed air to check if the internal seal is working. He said the transmission may be trying to apply 3rd gear earlier than I think, but unable to hold it due to insufficient pressure on the controlling circuit. Unfortunately a lot of the conversation was above my technical competency. They also told me to get a new detent solenoid even if mine looks fine, so I will do that. They weren't particularly hot on using the orange pressure regulator spring for my application, but thought it was a better idea than using the yellow spring of unknown origin. I should have asked what pressure they expect with this setup.

I also told them about the sound of something clicking back and forth when I tilt the valvebody and they said that is probably the spacer pin in the 3-2 shift valve. It floats inside the spring and that's normal.
That's a super good customer service scenario there. Sort of warms my heart to hear how much info they helped you with.
Old 04-05-2017, 07:10 PM
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Yeah they definitely went above and beyond helping me with the shift kit. Every time I've talked to them on the phone it's been like having a transmission class. Seriously cool.
Old 04-07-2017, 12:14 PM
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Last night I removed both the 2-3 valve assembly (top of photo) and the 3-2 valve assembly (bottom of photo). There were no issues with either; the valves all slide freely in their bores as they should.



The Transgo tech line gave me specifications for the springs. The outboard spring should measure 4lb 4oz @ 0.809in installed height. So I set a pair of calipers to 0.809in and compressed the spring against my kitchen scale (photo below). It was within a few ounces.



The inboard spring should measure 3lb @ 0.804in. It was less than half that (photo below). Less force from this spring should result in earlier 2-3 upshifts, but that does not explain my issue. I called Transgo and they agreed.



I went ahead and put the 2-3 and 3-2 valves back the way they were. Then I removed the 1-2 accumulator valve (below). Transgo has you remove the outboard spring from this assembly to help firm up the 1-2 shift. I removed and put this back into the valvebody.



Next I got back under the car to take a look at the case. Transgo suggested I air test the direct drum by applying compressed air to the associated feed holes on either side of the center bolt. At this point I discovered someone had plugged the reverse feed hole in the case with a screw-in plug (see top middle of photo below).



I removed the plug and found air would pass freely between the feed holes, indicating someone has removed one of the seals inside the direct drum. This is the internal version of the "dual feed" modification which allows fluid to feed both sides of the direct drum for better holding in 3rd gear. The plug is installed to prevent backfeeding the reverse circuit.

Transgo tech does not like the internal method, even though it seems to be a popular approach; they said it takes too long for oil to feed from the 3rd feed hole past the missing seals inside and they feel their method of doing the dual feed using their custom separator plate is a better approach since it uses both the 3rd and reverse feeds to simultaneously charge the direct drum. I have read that with the internal mod, it's important to lock out the 2-3 accumulator (as mine was) because of this point.

Whatever the case, the Transgo separator plate is not compatible with the internal mod, so if I leave it as is, I will have to use a stock separator plate. If i want to switch back to stock, I will have to pull the internals to do so.

That is all very interesting, but it still doesn't explain why I'm having issues with the 2-3 shift. So I went back to diagnostics....

With the plug reinstalled, I put air into the open feed to test the direct drum actuation. I could hear the direct drum actuating, but it also seemed like some air was leaking inside the transmission. It's hard to say because it was difficult getting the nipple on my compressor to seal into the case. I am going to try it again tonight. If the direct drum seals are leaking, that might explain my 2-3 shifting issue.
Old 04-07-2017, 12:51 PM
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Good luck tonight, great to see you are not being discouraged.
Old 04-07-2017, 01:29 PM
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Clint sorry for your loss.
It's never an easy time.

The Trans Go separator plate does not work with the internal dual feed mod. You will have to use the stock one.
Removing the seals causes an internal leak which feeds both sides of the direct drum for more capacity. The internal mod is an old drag racing trick.
Trans Go does it with their separator plate.

Let us know how it works out.


Mike
Old 04-07-2017, 02:38 PM
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Thanks Mike & Edy.

At this point he transmission has become a puzzle that I want to solve, so I'm not too frustrated. I'm enjoying learning how this thing works, but I'm also losing confidence the issue will be solved without pulling apart the internals.

Mike - Do you have any comments on how the internal dual feed mod compares to Transgo method? i.e. does the internal method have any significant downsides? Transgo recommended I undo the internal mod and use their separator plate, but I don't think it's worth pulling the transmission apart for. If I do end up pulling the transmission apart to figure out the 3rd gear issue, then I will need to decide which way to go.
Old 04-07-2017, 03:52 PM
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No expert but the Engineer in me is thinking there is something internally wrong like a worn out bushing or defective direct clutch pack. Fluid travels thru the shafts with holes that feed the clutch packs. Sealing rings are used on the shafts. If bushings are worn the sealing rings don't seal well causing pressure loss.
Currently building a 4L80E which is 75% Turbo 400.
Get a good book on rebuilding/modifying. There are many out there. It is not that hard once you can identify how it works.
Internal dual feed is my choice and is used by many builders.
Seals are left off the direct drum assembly and the center support creating an internal leak thus the pipe plug installed in the case. The plug seals the internal leak.
Pipe plug and omitting seals is free Transgo is $$.
Here to help anyway I can.


Mike

Last edited by LongIsland63SS409; 04-07-2017 at 04:00 PM.
Old 04-07-2017, 04:02 PM
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Thanks Mike. Transgo folks also think this is something internal. I sure hate to pull the trans, but maybe it's worth the time to go through it. The parts to rebuild are less than $200 and it seems like a weekend or two worth of work.

Why is internal dual feed preferred? Do you usually lock out the front accumulator when you do it? I've read about people blocking the feed port and removing the piston completely. Mine was locked down with nuts when I found it, but I undid that hoping to use the complete Transgo setup.
Old 04-07-2017, 05:10 PM
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Not sure about the front accumulator but the modified VB on my 4L80E are blocked off to give firmer shifts.
Nothing can go wrong with the internal dual feed but the Transgo VB could potentially leak.


Mike
Old 04-07-2017, 09:30 PM
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Here is a video air feeding the direct drum with about 30psi. Is this kind of internal leakage normal?


*EDIT* Here's someone else doing the same kind of test with the direct clutch out of the transmission. I don't hear the same kind of leakage in this one. Start at 18min


Last edited by -TheBandit-; 04-07-2017 at 10:19 PM.
Old 04-08-2017, 06:53 AM
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Part of the process for the internal dual feed is to drill a .060 hole in the back side of the drum to aid in exhausting the fluid.
I believe that is what you are hearing but it sounds like it's seating.
The internal leak is stopped by the set screw.

Mike
Old 04-10-2017, 02:52 PM
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Thanks Mike. So maybe nothing wrong with the seals in the direct drum. I am curious though if slipping in the direct drum would explain my issue? i.e. if it were slipping back to 2nd gear then grabbing again for 3rd gear, would that explain the cycling back and forth 2-3-2 and why it downshifts to 2nd under any kind of load?

Continuing on...

I got back under the car and decided to pull out the front servo for inspection. I found the e-clip broken and floating around in the assembly! That explains why this trans has never had engine braking in 2nd gear since I've owned it. I'll bet it was broken during the original build. This servo applies the front band which is only used for engine braking in L1/L2, as far as I know. Without the e-clip, I think the piston would just move up and down the shaft in the bore without pushing on the band. I'll pick up a replacement.



Next I put the Transgo pink spring behind the modulator valve. I confirmed it is still moving freely in the bore. I put a new vacuum modulator on.



Finally I pulled the rear servo to install a stiffer Transgo spring on the 1-2 accumulator piston located inside. The Transgo spring is on the right in this photo.



As I pulled apart the accumulator piston, I noticed the seals seem to a very free-floating fit. Take a look at this video.


Does anyone know if that type of fit is normal? I don't see how they could seal with that kind of fit unless they somehow rely on pressure to seal.

*EDIT* I came across this video. His seals look just as loose as mine at 17min 58sec:

Last edited by -TheBandit-; 04-10-2017 at 04:57 PM.
Old 04-10-2017, 06:17 PM
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I checked both 1-2 piston to the inner bore and case bore.
Both have a tight fit with the seal installed.
My trans is a 4L80E which has the same setup. Transmission has approx. 3,000 miles on it when the vehicle was in a bad wreck and pulled.

Mike


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