Rebuilt 4L80E slipping in forward

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5,767
Location
Fort Worth, Texas
Anywhere 19 is.....Don't forget that the Pressure Switch assembly is a major potential leak point as well. The Red Dot is where the feed for the Drive Pressure Switch is drilled through the Valve Body.

Look at the Plate Gaskets real well.....The valve body & case will leave clear sharp lines in the paper gaskets where it's sealing well.

ysMvvYy.png
 

Lindberget

Thread starter
Messages
21
Thanks! I get it!!
Every clutch but the OD holds a 40Psi short boost for about 3 sec or more with clear thump. The OD thumps but won’t hold pressure, it will not thump below 20Psi.
Is that normal?
Both spacer plate gaskets have perfect press patterns from VB and case.
Pressure switch assembly is new and seem to seal well..

I have drilled my old separator plate, JB- welded the pressure relief in the VB and will put it all back tomorrow.
Really hope it works and the clutches are not toasted..

Any final thoughts or checks?
If not every lead is towards that you cannot combine HD2 and internal dual feed.
I have found nothing wrong yet...🤔
 

Lindberget

Thread starter
Messages
21
Put the VB back today with stock separator plate, all eight check balls.
On the test drive it started out good, manual second is nice and firm! Rubber burns instead of clutches.
Still slipping when starting in 3rd and 4th thou. Almost like it wants to slip start from 3rd gear or something.

I dared to take it up in speed for more tests.
I can’t get it into 1st, it starts in second. EZ-TCU controller says 1st but I feel no shift when moving shifter from 1st to second at higher rpm.
It shifts nice and firm when shifting manual positions, 2nd to 3rd and later to 4th and lock up.
Once in 3rd or 4th at speed it seems quite responsive as well.
Checked pressures during shifts, 170-180 psi, not drops, even when slipping.

Any ideas? @clinebarger
 

Lindberget

Thread starter
Messages
21
So it only starts in 2nd when Hot??
It behaves the same no matter the temperature. Never slipping in reverse or second shifter position. Not slipping in first positions either but starts in second there as well.
Have not experienced 1st gear I believe.
I assume 1st gear wasn’t there before either but I couldn’t feel that with all the slipping going

Basically same tendency like before but with nice and firm shifts when starting in shifter position 1 or two and manually shifting my way up. Before it felt like it slipped everywhere..
 
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Lindberget

Thread starter
Messages
21
In addition to above.
Since I have pressure, all clutches are air tight. Since reverse and 2nd work, mechanically it could only be the low roller clutch?
Could it be something else in the VB leaking that I missed?

What could I have messed up with low roller clutch?
I Remember it was replaced with a new roller clutch, distance shim installed below and it should be in the proper direction as patterns basically match between drum and roller clutch.
What happens if low roller is not holding in 1st?

Some discussions on similar topic that you responded to in the past, @clinebarger

 

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Messages
5,767
Location
Fort Worth, Texas
In manual low.....The Lo/Reverse band comes on & holds the Reaction Carrier stationary, This would give you first gear even if the Lo Roller Clutch was completely missing.

You're likely going to need to tear the unit down, I realize that's not what you want to hear, But......It's part of building transmissions. And another piece of advice that's worth it's weight in gold.....Building blown/burnt-up cores doesn't always work out, There could be case porosity issues or a crack you can't see.

IF? the Intermediates Frictions & Steels welded themselves together....The unit will take off it 2nd no matter what you do externally.
 

Lindberget

Thread starter
Messages
21
In manual low.....The Lo/Reverse band comes on & holds the Reaction Carrier stationary, This would give you first gear even if the Lo Roller Clutch was completely missing.

You're likely going to need to tear the unit down, I realize that's not what you want to hear, But......It's part of building transmissions. And another piece of advice that's worth it's weight in gold.....Building blown/burnt-up cores doesn't always work out, There could be case porosity issues or a crack you can't see.

IF? the Intermediates Frictions & Steels welded themselves together....The unit will take off it 2nd no matter what you do externally.
Thanks @clinebarger!
Took the transmission out and disassembled it today.
I can’t find anything that might cause this.
All clutches and steels look fine. Measured the direct and forward clutch pack clearances and they were about 0.012inches from what they were when they went in.
So, missing first in manual low, starting in second. Not staring in first gear in gear selector 3 or D as well as slipping.
Have pressure and do have air tight clutches.
Experienced some leak in the direct, my drilled hole for the centrifugal apply fix leaked, I punched that together to rule that one out. The ball valve might have been slightly leaky.

I don’t dare to believe that was is so I did some testing on the valvebody circuits.
All electronics but the harness is new and the solenoids are tested. All sprags are in right direction.
I assembled only the VB and servos to the case. I put air supply to channel 2 in the case and blocked of some other passages leading to the pump.
If I understand it correct passage 2 should be oil supply. With this I tried running thru all shifting options with the solenoids.

P/N seemed to work fine. No difference on solenoid A energized.

Reverse worked with both reverse band pin moving and direct air in the case. Solenoid A did not do any difference.

D, when both solenoids off, forward clutch air, intermediate applied.
When energizing solenoid B direct applies.
When energizing solenoid A, nothing happens.
When energizing both, same case as for solenoid B energized.
Solenoid A is just clicking and sitting the solenoid leak but nothing happens..

Same for the other gear selections and combinations. Including manual low where front band and intermediate stay applied and rear band unapplied even if solenoid A is energized.
Is this a valid test method and what could be wrong?
1-2 valve looks ok..
Super hard to find a valvebody in Sweden, otherwise that would be nice to test to rule that out.

If it weren’t for that I already had my driveshaft shortened I would go back to my TH400 now, can’t get it figured out and it is killing me.
Appreciate your support and advice!
 

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Messages
5,767
Location
Fort Worth, Texas
The only clutch that the 1-2 shift valve (Solenoid A) controls directly is the Intermediate Clutch.....But it's Off not On.
With B off & A on.....No clutch is applied except the Forward Clutch which is applied by the Manual Valve.

Are you actually achieving Manual Low with the Shifter??.....As the Manual Valve hydraulically brings on the Lo/Reverse Band.....The Band CANNOT be "On" in 2nd Gear as that would Tie-Up the Geartrian.

Make sure none of the Shift Valves are installed backward.

Sure it's not time for a Vacation/Holiday to North Texas so I can build you a 4L80E.....Just pack light so you can take your 400 pound luggage back with you ;)
 

Lindberget

Thread starter
Messages
21
The only clutch that the 1-2 shift valve (Solenoid A) controls directly is the Intermediate Clutch.....But it's Off not On.
With B off & A on.....No clutch is applied except the Forward Clutch which is applied by the Manual Valve.

Are you actually achieving Manual Low with the Shifter??.....As the Manual Valve hydraulically brings on the Lo/Reverse Band.....The Band CANNOT be "On" in 2nd Gear as that would Tie-Up the Geartrian.

Make sure none of the Shift Valves are installed backward.

Sure it's not time for a Vacation/Holiday to North Texas so I can build you a 4L80E.....Just pack light so you can take your 400 pound luggage back with you ;)
Solenoid A does not shut air into the case, at least not when only feeding it with air from passage 2 and all other pump to case passages blocked.
The shifter moves from end point to end point. The spring holds the valve slightly from the inner most position, about 4 mm from even with the VB. Looks correct on how it blocks different passages, see picture.
How can the low/reverse band be controlled with the manual valve if it only applies in first gear and not in second? It must disengage when shifting from first to second when in shifter position 1, controlled by the solenoids?
Shift valves are in the proper direction.

Would have to take those 400pounds as a carry on if going to Texas 🤣

Will re write the phases I have passed in a new post to clarify my mix of Swedish and English.
 

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Lindberget

Thread starter
Messages
21
English is not my first language and since I have switched separator plate one time between all tests, the results and challenges might appear contradicting.
Happy to try to clarify!😁 Thanks for your patience!

The first section of the thread, when I experienced slipping in all forward gears, was with the HD2 set up.

Between the first part and the second part I disassembled the VB and replaced the HD2 separator plate with some other adjustments and the second gear selector was not slipping anymore.

Here it is again, from start.

After the full rebuild of this transmission, which I did with a lot of attention to detail and reading of yours and others advice in combination with the service manual, I experienced slipping in all forward gears. Only reverse was nice and firm, all other shifter positions slipped. It gained speed but slipping bad.

This is some info on the original build,

“1992 case, complete alto and kolene steels kit, Transgo HD2 kit and internally dual feed modification, fully rollerized, steel forward hub, case saver, new electronics, bearings, seals, EZ-TCU, 3200 stall converter.
Drilled pump against seal blow out, drilled strator against convertor drag, drilled 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. HD2 relief valve installed.
Rear end play 0.1 mm, front 0.2 mm. All clutch pack plays within spec. All sprags in correct direction.
All clutches and servos air tested. Some leak in 4th clutch, possibly due to strator seal ring gaps. Some leak in the direct, possibly due to hole drilled to prevent centrifugal apply”

At this point I had a great reverse but slipping in all forward shift positions. Transmission was indicating that it started in first gear but never engaged in first gear. Only started in second gear..
I had good line pressure according to below table. I had a stable pressure during slipping shifts, no pressure drop at all.

4b7086d1_8392_4918_9271_779d6b96abc7_fb3da6050c41b7bdec0cc8c4c97ae1afeb14f632.jpeg


DISASSEMBLY 1.
After this I dropped the pan and VB to make some modifications and further tests.
This is how it looked,
f1b8d57e_72e0_49b8_ac18_4b4e3985f11c_780d859aabe2127c9dc2b6f273c165071a2668b9.jpeg

I air tested everything again to confirm any leaks in the clutches. Same results as above.
I replaced the HD2 separator plate with a drilled stock one, same hole sizes as above.
I plugged the HD2 pressure relief valve.
I inspected that all valves moved in the VB and that solenoids and electronics worked.
I reinstalled with all 8 checkballs in place.
Replaced oil, filter and verified oil level.

After this modification I got a firm 2nd gear in 2nd shifter position.
Still slipping in 3rd and 4th shifter positions, still no 1st gear.
At this point I could safely manually get it up to speed and it had a noticeable shift from manual 2nd to manual 3rd, 3rd to 4th and lock up.
Stable high pressures between all gears. Above my max pressure reading of 200Psi.

DISASSEMBLY 2
Removed the complete transmission and did a full disassembly. This time the oil was clean.
I can’t find anything that causes this.
Forward and direct clutch packs are about 0.012’ looser then when installed, all sprags correct..
I do not have proper vacuum testing tools for the VB. Very small leak in the AFL, last compartment, with the elongated end section of the valve. That does not seem to bad but hard to know when I can’t measure. That part of the valve looks nice but the middle part looks questionable,
9a5158d2_77a3_4548_a0f4_276243d06455_9831845a6d7b6be1e13468c1c83690bcea8e9d80.png

51fedea5_fbf7_4cc4_85ac_54f6b787d9ed_2f1683670209cec8ff48ddbdeecc052bef4dd094.jpeg


Since there are no 4L80e VBs in Sweden to what I can find yet, I tried air testing the VB together with the case to see which clutches and servos get air at what point.
This testing method is questionable and made up by myself as I lack further ideas.

I assembled only the VB and servos to the case. I put compressed air supply to channel 2 in the case and blocked of all other passages leading to the pump.

2de4cab5_e4e8_4f22_8675_77db4bd086f6_f4dee4c593bade47e6b9db2fd26494a9b89f30b3.jpeg


If I understand it correct passage 2 should be line pressure supply. With this I tried running thru all shifting options on the gear selector together with energizing the two shift solenoids.
I used following to guide me on what combination to set for what desired state.

9f66f6c5_1b0b_41b7_80e0_9c9a770a13da_3694780569c227fae74a9cd011cfe8f13a8b6dd8.jpeg



P/N, no clutches engaged. No difference if solenoid A is energized of not.

Reverse worked with both reverse band pin moving and direct clutch air flowing into the case. Solenoid A did not do any difference.

D, when both solenoids off, air flows thru forward and intermediate case channels.
When energizing solenoid B air flows into direct case passage as well.
When energizing solenoid A, nothing happens.
When energizing both A &B, same case as for when solenoid B energized.
Solenoid A is just clicking but nothing happens.

Same goes for manual 3rd. Solenoid A does not make a difference.

In manual low, front band and intermediate stay applied and rear band unapplied even if solenoid A is energized. That is the state for 2nd gear in 2nd shifter position.
Isn’t solenoid A supposed to adjust that for the transmission to shift to 1st gear?

Is this a valid test method and is it enough to feed air to passage 2 in case?

ae55b406_f3f5_405d_828a_47f9cd92ac85_a71b70ff68ef3cbc9321e5e19c7d64b7cc6aca24.jpeg

1-2 valve looks ok.. but it does not seem to make a difference to anything….

Hope this makes my challenge easier to follow.
Appreciate suggested next steps!
Thanks!
 
Messages
5,767
Location
Fort Worth, Texas
Manual Lo.......

*1-2 Shift Solenoid.....
Energized, 1-2 signal Fluid pressure forces 1-2 & 3-4 shift valves to the extreme left.

*2-3 Shift Solenoid.....
De-energized, 2-3 signal fluid exhaust through the solenoid body.

*1-2 Shift Valve....
1-2 signal fluid pressure holds the 1-2 shift valve extreme left. The actuator feed and drive pressures supplied to the 1-2 shift valve are blocked.

*2-3 Shift Valve.....
Spring pressure and the D21 fluid pressure from the Manual Valve hold the 2-3 shift valve to the extreme right.

*3-4 Shift Valve.....
1-2 signal fluid pressure forces the 3-4 shift valve to the extreme left.

*Lo/Reverse Band Servo.....
Lo fluid pressure from the manual valve is directed to the #7 checkball & to the Lo/Reverse Band Servo thus applying it.

JzOVM89.png

dZWHcGK.png

3NBRmUE.png
 
Messages
5,767
Location
Fort Worth, Texas
First Gear (D4).....

*Same as Manual Lo except the Lo/Reverse Band is not applied and PND43 fluid is available.
*D321, D21, & Lo passages are blocked by the Manual Valve.

*1-2 Shift Valve.....
Drive Fluid pressure from the manual valve is held at the 1-2 shift valve in order to be utilized in other gear ranges.

*2-3 Shift Valve....
Drive Fluid pressure from the manual valve is held at the 2-3 shift valve in order to be utilized in other gear ranges.

*3-4 Shift Valve.....
1-2 signal fluid pressure forces the 3-4 shift valve to the extreme left. PRN fluid pressure is blocked by the manual valve.

Nothing really happens in this range except the 1-2 Shift Solenoid needs to be energized & hold 1-2 Signal Fluid from exhausting......Though the 1-2 Shift Valve needs to be held to to the extreme Left to block Drive Fluid from entering 2-3 Drive Fluid passage.

AOpym2q.png

n3CNCfM.png
 
Messages
5,767
Location
Fort Worth, Texas
Is the 1-2 (A) Shift Solenoid leaking? Trying swapping the Solenoids & air check it again. Yes....I understand they don't swap per-se, But just to prove it out with your air testing.
 

Lindberget

Thread starter
Messages
21
Is the 1-2 (A) Shift Solenoid leaking? Trying swapping the Solenoids & air check it again. Yes....I understand they don't swap per-se, But just to prove it out with your air testing.
Thank you @clinebarger .
Both solenoids are 100% air tight.
I Will work self true the fluid paths and see if I find something. Also got hold of the GM manual with all fluid charts for all gears.
Will try to build a vacuum tester.
I just don’t see how the VB could leak so bad that 1st do not engage at all.. especially without any ocular signs of wear..
Any common critical areas for the 4l80e?
Remember the direct and forward were toast originally. Converter also crap.
Really appreciate your help!!! Thanks!
 
Messages
5,767
Location
Fort Worth, Texas
The AFL valve/bore is a common wear point, Especially on "early" units. But....It will usually lose 4th/Overdrive long before 2nd gear starts occur.

I assume you're running a later PCS/EPC solenoid & the supporting mods??
 

Lindberget

Thread starter
Messages
21
Early 4L80E's used a TH400 style Front/Intermediate Brake Band, Late 4L80E wide band & piston components DO NOT swap
Yes, have the later version PCS with the VB mod. I have a 1’ band, ordered as the early style.
Middle section of the AFL does not look good. Isn’t it the end section that needs to have a good vacuum?
 

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Lindberget

Thread starter
Messages
21
Sorry for late reply @clinebarger.
Built myself a vacuum check tool with some left over piping and checked my VB vacuum this weekend.
See picture for readings. There were three spots below 17.
Lo/reverse checkball at 14 and reverse checkball at 12.
Then I don’t understand how Sonnax wants me to test the AFL solenoid filter and end plug by setting vacuum to red marked cavity, this cavity connects thru the filter to the 2-3 shift valve….Just sealing the red marked area gives me a clear 0 hg-in.
I have replaced the filter set up with trans go’s solution, o-ring sealed plug against manual valve, new filter, red spring, new end-plug.
Any ideas on my readings?
I really just want to find a clear cause to fix right now, sick of thinking🤣
Any ideas on AFL wear from last post?
 

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