First off. Been lurking and searching for a long time. Good information in here.... but I have a weird combo of issues going on and I’d rather pinpoint it this round of rebuild instead of chasing ghosts. Searched, came up with a few answers but nothing definitive.

Background:
2010 Silverado 4wd 6.0L (swapped)
4L60e (on 2nd rebuild)
35’s with 4.56 gears
212/218 TSP cam

So short expl.

First transmission rebuild covered by dealership, no questions asked. Second rebuild done by myself after the 6.0 swap because of obvious horsepower increase. 3-4 clutches were fried. Rebuilt with transgo shift reprogramming kit, boost valve, sonnax servo kit, z-pack 3-4 clutches, wider red 2-4 band, all pinless accumulators, factory transmission cooler and probably more that I can’t remember.

New problems occurring over last few months:

- 3rd to 4th gear shift flare (weird) when accelerating hard, and now a definite slip in 4th to 3rd downshift under power. It’s definitely going to need another 3-4 pack.

- starting from a stop, truck feels like it slams/slips into gear. Almost like popping a clutch too quickly, or starting from second and quickly downshifting to first. If that makes sense.

I recently swapped all solenoids in valve body to rule those out, no change.

Issues get exaggerated/progressively worse as trans temps increase.

No other issues to report. Truck is very strong in every other gear change. 1-2 is solid, 2-3 is even strong.

I’ve seen posts with sprags, over run clutches, pump issues, burnt bands, servo issues; but none quite explain what’s happening to mine.

The transmission is completely normal for “Sunday driving” but not for anything more aggressive.

 

Are you completely positive/ certain that the "Shift-Flare" or "Unusual-Shift" that is being experienced during the 3rd-Gear to 4th-Gear Up-Shift...
And NOT the 2nd-Gear to 3rd-Gear Up-Shift?

A 2nd-Gear to 3rd-Gear Up-Shift issue is far more common and far more complex than a 3rd-Gear to 4th-Gear Up-Shift issue.
Please double-check and triple-check that this is correct.
Either way, once you provide any new information/ complete the tasks that I ask of you...
We will make progress.

Please do the following before the Forum Members here proceed in assisting you with trouble-shooting/ diagnosis:

-Ensure that the ATF Level is FULL or preferably 1/8" above the FULL-Mark on the Automatic-Transmission dip-stick.
(The Engine/ Transmission must be up to operating-temperature. Clean and read the Dip-Stick with the gear-selector in the park-position).
-Ensure that the Color and Consistency of the ATF are in good-health.
(Bright red in color with no debris in the fluid).
-Obtain and use an Automatic-Transmission Line-Pressure test gauge...
(Record the Line-Pressure for each gear-range, both at idle and at approximately 1,200 - 1,500 RPM).
-Ensure that NO Engine related, Transmission related, or Emissions related Diagnotic-Trouble-Codes have been set or recorded.
(Record and post any DTCs if present).

Post your findings and we shall continue.

 

I might have misused the “flare” terminology. The rpms rise from around 2500ish to 3000+ before coming back down to around 2000 for the 3-4 shift.

I’m certain it’s the 3/4 shift also because keeping the shift lever in 3rd gives me good solid shifts under acceleration at most throttle positions. BUT Trans temps over 180, I can get it to slip in the 2-3 shift if I really get on it.

I put new fluid and filter in after the solenoid swap to rule out bad oil or a clogged filter.

I just ordered a pressure gauge, should be here on Tuesday.

HPTuners says no active trans codes or engine codes other than the ones I have turned off for exhaust related..... you know.

I’ll get the pressures recorded and will report back.

thanks a ton

 

What did the fluid look like when replacing the solenoids?

 

It was cloudy and black. Magnets had black sludge on them. Which is why I was already planning to do the 3-4 clutches again.

Took the truck for a ride today to try and get a video of the revs with the shifts and I basically have no 4th anymore and barely 25% throttle in 3rd.

Probably gonna plan on taking it out middle of the week.

The other issue that stumps me is the jerk into 1st gear from a stop. I can manually put it in 2nd also and it jerks the same too, but feels different than first gear. So it doesn’t feel like it’s trying to start off in second, then jumping down to first gear. Any ideas?

im sorry for jumping all over with this but I’m gonna try and gets parts ordered before I pull it out the truck

 

Another thing too, not sure if this makes sense or helps narrow down an issue. But something I noticed but didn’t think to mention was an issue in a manual downshift from 4-3. It’s a rough downshift. Not a smooth transition but a jerk, like 3rd was still applied while in 4th.

don’t know if that makes sense to anyone that knows more than me

 

Well of course there a few different things that could be going on...
We will have to see what the Line-Pressure readings are.

If the Line-Pressure is good in all gear ranges (especially above engine idle-speed)...
For a 3rd - 4th up-shift: You are going to have to look at the 2-4 Band Servo Assembly.
Hopefully your vehicle has ample room underneath to remove the 2-4 Servo without lowering or removing the Transmission.

It is possible that the 2-4 Band has worn enough to not properly apply well enough to shift into 4th gear.
Some times the 2-4 Servo Apply-Pin can be lengthened enough to obtain some use of 4th gear again,,,
But most of the time this would be an indication of the 2-4 Band being at the end of its life.

Now if there is an issue with the 2nd - 3rd Up-Shift... or there is an issue with both the 2nd - 3rd, and the 3rd - 4th Up-shift...
There will be much more to discuss.

I would much rather wait for the data or any more information that is available than type this kind of stuff constantly.
Hopefully the Transmission is still making good Line-Pressure.

Good Luck and Have Fun!!!

 

Well no luck on an update. Pressure gauge for the trans came in. Ordered a 0-300 psi. And the actual gauge only goes up to 150 psi. Not sure if that would be suitable after reading that some pressures need to be 200ish

 

Gauge needs to go to at least 200 for a stock trans.

 

Ok so got the whole gauge thing to work.


Trans temp above 135 when all these pressures were taken.

Park at idle - 90 psi

1st gear - 110-120 psi at idle. 150 psi at 1200-1500 rpms. Brake boosting I can get the pressure to spike 240 if I stab the throttle.

2nd gear. Same result 1st. Give or take 5 psi for needle jump.

3rd and 4th - 130-150 psi at 12-1500rpms also. 3rd slip causes pressures to rise steady and basically no 4th gear still.

I’m gathering from this that it might not be a pump issue?

 

I would start looking at the 2-4 band/ servo end-play/ travel...

 

Instructions on how to check servo pin travel.

 

Sorry for the long period of time between updates, been away from my truck at work.

Pulled transmission. Disassembled and cleaned all pieces and parts. No surprise that the 3-4 clutches were toast.

Watched tons of videos. Read pages upon pages of issues. Ended up putting all new clutches in the input drum, new apply pistons in the input drum. New Z-pack for the 3-4 clutches. New 2-4 band. New filter. Flushed the entire system with like 10 gallons of fluid.

Everything went together good. Reinstalled in the truck. No issues. Trans still works, has all 4 gears, and still all the same issues.

Just to recap....

Slow, sluggish 3-4 shift when accelerating “spiritedly” and only the 3-4 shift

Rough manual 4-3 downshift like something isn’t disengaging and it jerks when cruising

And the slip then sudden harsh engagement in first gear from a stop. (Low roller clutch? Or low/reverse?) didn’t dig that far into the lower part of the trans.

Pump pressures are good if not on the high side, I can adjust pressures in HPTuners and the trans responds.

2-4 servo pin was in spec. Pin travel was in spec.

Could it be something in the valve body? Maybe a rebuild kit for it? Its a 2010 and it’s a different body than the 2006 trans I had as a parts one...

Really could use some tips, really don’t want to pull the whole trans again.


Thanks a ton

 

Damn Z-Pack!!!
Damn Precision Transmission on YouTube!!!

Did you have the Valve-Body Vacuum Tested?
If not... this is the very next task to have done!
There can be a ton of 3-4 clutch circuit leakage from the Valve-Body.
More than likely you are going to need Sonnax O-Ring End-Plugs for the Valve-Body and Abuse-Valve Plugs.

 

I love Precision transmission....he can tear down a tranny in 5 min.....no clue how he builds one tho

 

LOL! You do not want to know... Trust me!

 

If it were me, I would start by replacing the servo pistons and seals and considering a new or rebuilt valve body. This is sounding like multiple problems and those two suggestions are likely to fix at least a few of the problems. Every 3->4 shift problem ever reported on this forum was due to a problem in the servo or the valve body.

 

Yes there are multiple 3-4 clutch circuit leaks through multiple valve-train...

 

come on Vor...make some U tube vids....put him to shame ! everyone of his vids is nothing but a teardown and complaining about the other shop who did a crappy build....he has YET to even begin to explain how to do a rebuild ...besides tellin viewers to use a z pak

 

LOL!
Honestly, a Transmission re-builder does not need to understand how the transmission operates/ is designed... in order to rebuild a stock unit.
They just need to learn the disassembly, and assembly processes in full (Finding wear and tear, Establishing proper clearances, Etc).

However, they pretty well damn know how the transmission operates/ is designed... in order to modify a unit...
And ACTUALLY IMPROVE IT!