Rebuilt 4L80E slipping in forward

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Jun 4, 2021
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4L80e Saturday challange.🍻
Just rebuilt my transmission during winter and just had a testdrive.
To my big disappointment it is slipping in forward gears. Moves and shifts but acts like a rubber band. Reverse is really firm!!
1992 case, red alto and kolene steels, Transgo HD2 kit and internally dual fed, fully rollerized, steel forward hub, case saver, new solenoids, bearings, seals, EZ-TCU, 3200 stall.
Drilled pump against seal blow out, strator against convertor drag, rear strator support and overrun clutch housing for better flow and finally direct drum to prevent centrifugal apply. HD2 Separator plate drilled to 2nd: 0.11inch, 3rd: and 4th: 0.125inch
Omitted 3rd clutch and reverse checkballs.
Rear end play 0.1 mm, front 0.2 mm. All clutch pack plays within spec.
80% sure intermediate sprag is in right direction...
Pressure according to picture, when increasing pressure in TCU 3rd and 4th increases as well. Most things checked more then twice..😭
Any suggestions before I start splitting it again..😂
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In addition, if you have not done so, I suggest to post your question at the GM truck and Diesel truck forums (a few of them).
This is an older transmission, there should be a lot of experience on this transmission.
 
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Were the Forward Frictions burned when torn down originally? The Forward Drum is replaced more often than not for wear in the sealing ring lands.

Was the Forward Drum inspected thoroughly during the rebuild?

In a stock configuration....You could simply power brake the vehicle, If the Input Speed Sensor showed RPM, The Forward Clutch is slipping.
Unfortunately.....Aftermarket Controllers do not support ISS sensors
 

Lindberget

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Thanks for replying @clinebarger!
Before the rebuild both forward and direct were burnt. Converter had some metal piece inside and the bearing between converter and pump was really bad. Brought a new pump and converter plus I did the full rebuild.
No signs of the seal rings digging in on any components. Could I have compressed them too much during resizing?
Would be good with input sensor on the AM controllers for alarms and error codes!
I could probably just put the output connector to the input sensor and see if it moves during power braking. Will do that and share the outcome today!
Any other thoughts? What about using both HD2 spearator plate and internal dual feeding combined? Would that create a leak instead of dual feeding?
Thanks for supporting!!!🙏
 

Lindberget

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Were the Forward Frictions burned when torn down originally? The Forward Drum is replaced more often than not for wear in the sealing ring lands.

Was the Forward Drum inspected thoroughly during the rebuild?

In a stock configuration....You could simply power brake the vehicle, If the Input Speed Sensor showed RPM, The Forward Clutch is slipping.
Unfortunately.....Aftermarket Controllers do not support ISS sensors
Connected my EZ-TCU output sensor connector to the input sensor instead.
I had the same rpm on the input sensor as engine rpm in both park/neutral, reverse and forward gears. Power breaking or not..
 
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The Forward Drum should lock down in Reverse & all Forward Ranges while the Output (driveshaft) is stationary. For Reverse.....The Direct Clutch holds the Forward Drum via the Forward Clutch Backing Plate.
 

Lindberget

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The Forward Drum should lock down in Reverse & all Forward Ranges while the Output (driveshaft) is stationary. For Reverse.....The Direct Clutch holds the Forward Drum via the Forward Clutch Backing Plate.
Thanks @clinebarger!! What does it mean that the input sensor then shows the same rpm as the engine in all combinations according to above?

Could it be me combining the HD2 separator plate and the internal dual feed mods that creates a big leak?
 

Lindberget

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Several sources pushed me into replacing the HD2 separator plate and install the stock one and all 8 checkballs instead. What do you think about that @clinebarger?
While doing this, should I also block the HD2 relief valve even if I am running with HD2 boost valve that is not self regulating?
What about this amount of friction material contamination, ok to run?
 

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Joined
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Thanks @clinebarger!! What does it mean that the input sensor then shows the same rpm as the engine in all combinations according to above?

Could it be me combining the HD2 separator plate and the internal dual feed mods that creates a big leak?

At face value.....The Forward Clutch is slipping. But it would have a hard time moving forward at all & would at least slow the Forward Drum down as not much torque is being applied with the engine at idle with a 3200 stall converter.
**And as I said earlier.....Reverse works well (Correct?)....So the Direct Clutch would hold the Forward Drum stationary in Reverse.
I have to say this test is inconclusive for now.

Running an HD2 with Internal Dual Feed mods will NOT causes issues that aren't already inherent to using a 3-piece Separator Plate.......Crossleaks are a possibility, BUT.....Thousands have used the HD2 without issues.

There is one other thing that could be an issue......IF you left the Center Lip Seal in the Direct Drum & Plugged the Reverse Passage in the Case.....You effectively eliminated the Dual Feed Mod in Direct & cut Reverse holding power in half.

The ONLY reason to run a HD2 Plate is so the unit can be Dual Fed without tearing it down as it basically plugs the Reverse Feed & routes 3rd Clutch Feed to both the Reverse Feed & 3rd Clutch Feed at the Center Support.
 
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Several sources pushed me into replacing the HD2 separator plate and install the stock one and all 8 checkballs instead. What do you think about that @clinebarger?
While doing this, should I also block the HD2 relief valve even if I am running with HD2 boost valve that is not self regulating?
What about this amount of friction material contamination, ok to run?

That's not good as I'm assuming there isn't many miles on this unit?? Even if you were running Graphite/Hi Energy which do "Fluff Off" some black stuff during break in......That's WAY too much! Being you used Alto Red's.....You have a some Crispy Frictions!!!!

Factory Hi Energy Borg Warner frictions have been proven in applications well over 1000 RWHP. Not that using Red Eagles is the core issue here as you likely have a leak in the Forward Clutch Circuit. I can't even imagine what a set of Red Eagles & Kolene Steels cost in Europe??

You will need to go back over this unit with a fine tooth comb which will include air testing the Forward Clutch on the bench. I guess it's possible to shrink the Input/Turbine Shaft sealing rings too much.....But new rings generally expand back out naturally. Maybe one got rolled over during assembly?
 

Lindberget

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At face value.....The Forward Clutch is slipping. But it would have a hard time moving forward at all & would at least slow the Forward Drum down as not much torque is being applied with the engine at idle with a 3200 stall converter.
**And as I said earlier.....Reverse works well (Correct?)....So the Direct Clutch would hold the Forward Drum stationary in Reverse.
I have to say this test is inconclusive for now.

Running an HD2 with Internal Dual Feed mods will NOT causes issues that aren't already inherent to using a 3-piece Separator Plate.......Crossleaks are a possibility, BUT.....Thousands have used the HD2 without issues.

There is one other thing that could be an issue......IF you left the Center Lip Seal in the Direct Drum & Plugged the Reverse Passage in the Case.....You effectively eliminated the Dual Feed Mod in Direct & cut Reverse holding power in half.

The ONLY reason to run a HD2 Plate is so the unit can be Dual Fed without tearing it down as it basically plugs the Reverse Feed & routes 3rd Clutch Feed to both the Reverse Feed & 3rd Clutch Feed at the Center Support.
Thanks! The car moves forward but not at idle, starts to move at about 2000 rpm. Once moving it continues to build speed but if reving it is not following.
Reverse is perfect, need to brake not to move at idle.
Regarding HD2 combined with internal dual feed. I also left out 3rd and reverse check all, could that combo create a leak in forward? I have 3 people telling me this is it but your opinion ways more than 10 other ones!
That will definitely my next move. My path before your post was to replace the separator plate and put all 8 cballs in place. Now I am hesitant again..

I removed the center seal in the direct, removed second ring from top on strator and blocked both center support and case, all according to your guidelines.

Read up on all the details of the rebuild once I had bought all parts, old separator plate had some wear so since the HD2 was in hand I used it instead. Parts are ridiculously expensive here in Sweden, bought it in US and had it shipped by sea.

It has not been driven more then 2 miles and some power brake testing. Disappointing to see the wear.. Is there no chance they survived, trans has been below 180 degrees at all times?
There are no twisted or rolled over seals.
Can the forward clutch be air tested in the car? Where can it leak this bad?
Thanks for your support @clinebarger!!
 
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Did the HD2 kit instruct you too remove the #11 (3rd/Rev) Checkball? The old HD2 kit did.....But I haven't seen one in about 10 years.

Yes, The forward clutch can be air tested with the Valve Body dropped....
*Locate passage #19.
*There will be a hole at the front on the case that is horizontal.....Enters the Pump Cover.
*As the hole is at a 90° angle....You may have to get inventive with the air nozzle to get it to seal. I use vacuum hose on my nozzles to create a seal.
*You should have a pretty tight seal.

#19 passage enters the Pump Cover & goes straight to the first set of sealing ring on the Turbine Shaft, Through the Shaft to the second set of sealing rings, Then into the Forward Drum.
*The Red Arrow in the Pump Cover diagram point toward the Cup Plug that's a possible leak point if taken out & not put back in.
*The Pump to Case Gasket being torn or mispositioned would cause a leak.
*The Stator Sleeve that the first set of sealing rings seal against being damaged.
*Sealing Rings damaged
*Forward Drum Sealing Ring Lands damaged.
*Bleed Checkball in the Forward Drum blown out.
*Cracked Forward Piston (Common on Aluminum 4L80E pistons)
*Damaged Piston Lip Seals.
*A Steel or Cushion Plate getting under the ledge in the drum, This can cause the piston to only partially apply in-turn burning the clutch up



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It is my professional opinion to get rid HD2 altogether....Except the Accumulator Valve spring, 2nd Clutch Accumulator Spring, & Boost Valve. (Your pressure testing shows the Boost/Torque Signal system to work well)
*Buy a replacement Transgo Plate (48-PLT-01), Or GM# 24240312 is only about $8 here in the states, I'm assuming you know about the PCS/EPC differences between early & late units?......You have a early pan so I'm assuming you have a early unit??
*Return the #11 Checkball arrangement to stock.
*Install all 8 checkballs in the case (If you deleted the 3rd & 4th Accumulators.....Your can omit #5 & #6 like shown in the picture above)
 

Lindberget

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Awesome @clinebarger!
#11 checkball is still in. It is #9 and #8 that are out.
I will pressure check passage 19 later today!
Cannot recon any cup plug around there, need to take a look at that.
Got a new pump so if the cup plug is in the pump and it was not in in the new one, that could be it. Where should it be?

If passage 19 is not leaking, is it worth trying to put it together without splitting the trans or are the clutches gone anyway?
That would not give me a conclusive reason either.. If it is not the combination of internal dual feed and HD2 kit that is the problem?

Air tested through both bolts under the VB @40Psi. Those had a clear thumping noice with a short air spray, the rear one held air for about 10 sek while the front just for 2-3 seconds. Sounded good to me.

Sorry for the speculation, time zones delay the discussion 24 hours every post so trying to move multiple steps over here:)

Will post the 19 air results soon.
Incredibly thankful @clinebarger! So much knowledge sharing! Thanks!
 

Lindberget

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Had a hard time following the charts you posted.
Seems that passage 19 in the case connects to passage 40 on the pump, not 19.. Passage 40 on pump ends up between the outer seal rings on the strator which connects to the overdrive clutch. This means the red arrow marking where to air test marks testing the OD clutch.
The passage 40 in the case connects to passage 19 on the pump. This goes to the inside of the pump and should go to the forward clutch?
Does that make sense?

OD also holds pressure for about 2-3 seconds starting with a clear thump...

Forward clutch or passage 40 in case/19 in pump has a clear thump but is really quick back.

Don’t know how they all should feel but they all clearly thumped, air hose was pressurized but some held pressure longer then others.
Have a video but does not seem possible to post in this forum..

What does all these tests indicate?
I seem to have pressure even if too high in 1st and 2nd..
Seem to have good air test results
To me that leaves the valvebody..

How are fluids traveling in the valve body to be able to loose the pressure in forward there?

Thanks again @clinebarger! Learning loads!!
 
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Passage 19 is the Forward Clutch & Passage 40 is the Overrun Clutch.

Air will escape from the Step Cut seals on the Stator....So a quick release is normal on the Overrun clutch.

The Pump Cover diagram I posted is correct, It's a view of the BACK side of it.....Not the Front.....Below is a view from the front.

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