4L60E Keeping the overrun piston applied all the time.
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4L60E Keeping the overrun piston applied all the time. OK so I have a 94 pre pwm 4l60e kicking my but. It broke the snap ring out of the 3-4 drum (again) so I replaced it with a sonaxx drum. Changed to all steel pistons per their instructions. Pressed out my old input shaft and pressed it into the new drum per the instructions. cleaned all the bits and pieces out of the case went back together with new high energy frictions and steels. Air tested everything.. Now it applies the overrun clutch in OD, so when the pcm commands 4th, it will not shift and when I let off the gas it locks up the whole trans up, and slides the rear end, smokes the coast clutch frictions and the 2-4 band. If I drive around in (drive) it drives fine bangs the 1-2 shift and then the 2-3 shift. it will do the same in OD as long as I stay below 55 mph (that's where 4th is commanded to shift at). As I drive I can tell the overrun clutch is on even in OD (where it should never come on) as I slow it will down shift very hard (like you pulled it down into 2nd then into first) manually. There is no free wheeling it is engine braking anytime you coast. I have pulled it apart a number of times checking all I could think of. I have gone the threw the stack thinking I forgot a wavy or something small but I cant finger it out. any help would be great. thanks
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From: Fort Worth, Texas
You didn't go into detail how you went about air testing the Input Drum, Here is how I do it.
Take an old Sun Shell, Cut the Splined part off, This will give the pump a flat place to sit.
With the Input Drum (Shaft up) on a bench, Stack the Reverse Input Drum & Pump assembly on top of the Input Drum just like it does in the Trans.
Take the entire assembly (Holding it together) & place it upside down on the Sun Shell.
Apply air to the Forward Clutch feed hole on the Pump Cover, The Input Sun Gear should Overrun in 1 direction, & Lock in the other direction.
Apply air to the 3-4 Clutch, Again, The Input Sun gear should overrun in 1 direction, (The Forwards will "soft" apply....Non-Issue).
It is helpful to have someone hold the Input Drum still while you apply the air & work the Sun Gear.
Let us know the results.
Take an old Sun Shell, Cut the Splined part off, This will give the pump a flat place to sit.
With the Input Drum (Shaft up) on a bench, Stack the Reverse Input Drum & Pump assembly on top of the Input Drum just like it does in the Trans.
Take the entire assembly (Holding it together) & place it upside down on the Sun Shell.
Apply air to the Forward Clutch feed hole on the Pump Cover, The Input Sun Gear should Overrun in 1 direction, & Lock in the other direction.
Apply air to the 3-4 Clutch, Again, The Input Sun gear should overrun in 1 direction, (The Forwards will "soft" apply....Non-Issue).
It is helpful to have someone hold the Input Drum still while you apply the air & work the Sun Gear.
Let us know the results.
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Instead of an old sunshell, I have been using a very thick and stiff 6"x6" cardbox box.
Note that some air leakage is normal from between the pump halves and from the bleed hole in the input drum for the 3/4 circuit. However all the clutches should apply with 40lbs air and verify that they also release.
I didn't know that the overrun clutches have to release for 4th gear to work properly.
clinebarger: didn't the early 4L60E have a different forward clutch setup with thinner frictions? Isn't it possible that if you use late-model forward frictions with the old backing plate that the overrun clutch will run out of clearance?
I have only worked on '98 and later models but have read about forward/overrun differences in the very early years.
Note that some air leakage is normal from between the pump halves and from the bleed hole in the input drum for the 3/4 circuit. However all the clutches should apply with 40lbs air and verify that they also release.
I didn't know that the overrun clutches have to release for 4th gear to work properly.
clinebarger: didn't the early 4L60E have a different forward clutch setup with thinner frictions? Isn't it possible that if you use late-model forward frictions with the old backing plate that the overrun clutch will run out of clearance?
I have only worked on '98 and later models but have read about forward/overrun differences in the very early years.
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Yes thank you for the detailed pictures they are great. but sadly that's how I was shown how to air test. But I also air test the 3-4 drum by blowing air gently in the holes in the shaft of the 3-4 drum without any clutches or steels only the pistons you can test the overrun piston that way. All tested good.
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The clearance on the forward clutches was good.The snap ring for the Forward clutch backing plate went in as normal.
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Verdad Gallardo TECH Fanatic
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From: Fort Worth, Texas
clinebarger: didn't the early 4L60E have a different forward clutch setup with thinner frictions? Isn't it possible that if you use late-model forward frictions with the old backing plate that the overrun clutch will run out of clearance?
I have only worked on '98 and later models but have read about forward/overrun differences in the very early years.
I have only worked on '98 and later models but have read about forward/overrun differences in the very early years.
All 700's & 60E's have the same Overrun stack.
Yes thank you for the detailed pictures they are great. but sadly that's how I was shown how to air test. But I also air test the 3-4 drum by blowing air gently in the holes in the shaft of the 3-4 drum without any clutches or steels only the pistons you can test the overrun piston that way. All tested good.
I have only seen this issue when the Inner lip seal on the Forward Clutch Piston is torn during assembly (When using Steel Pistons, Aluminum pistons can crack causing the same), Allowing forward clutch oil to enter the Overrun piston apply area.
With that being said, If your sure there is no cross leak in the drum due to the reasons above or other unforeseen reasons.....Means you have a cross leak somewhere else.
The Pump Cover is a unlikely spot, The Overrun feed is all by itself next to a pump bolt.
In D4, The Overruns are isolated from any kind of apply oil, D1/D2/D3 oil has to be present for the Overruns to apply, In D3, The 2-3 shift valve has to shift for the Overruns to apply...Meaning the trans has to be in 3rd gear for D3 oil to reach the Overruns. In D1/D2, The Overruns are applied directly by the Manual Valve.
However D4 oil & Overrun apply are next to each other in a few places in the Case passages, This kind of cross leak is usually visible on the Separator plate gaskets.
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'82-'85 700R4's had thicker forward frictions & thinner steels, '86 & up 700's & 60E's use the same forward frictions & Steels.
All 700's & 60E's have the same Overrun stack.
Cool, You did made sure the Sprag/input sun gear could overrun with the Forwards applied?
I have only seen this issue when the Inner lip seal on the Forward Clutch Piston is torn during assembly (When using Steel Pistons, Aluminum pistons can crack causing the same), Allowing forward clutch oil to enter the Overrun piston apply area.
With that being said, If your sure there is no cross leak in the drum due to the reasons above or other unforeseen reasons.....Means you have a cross leak somewhere else.
The Pump Cover is a unlikely spot, The Overrun feed is all by itself next to a pump bolt.
In D4, The Overruns are isolated from any kind of apply oil, D1/D2/D3 oil has to be present for the Overruns to apply, In D3, The 2-3 shift valve has to shift for the Overruns to apply...Meaning the trans has to be in 3rd gear for D3 oil to reach the Overruns. In D1/D2, The Overruns are applied directly by the Manual Valve.
However D4 oil & Overrun apply are next to each other in a few places in the Case passages, This kind of cross leak is usually visible on the Separator plate gaskets.
All 700's & 60E's have the same Overrun stack.
Cool, You did made sure the Sprag/input sun gear could overrun with the Forwards applied?
I have only seen this issue when the Inner lip seal on the Forward Clutch Piston is torn during assembly (When using Steel Pistons, Aluminum pistons can crack causing the same), Allowing forward clutch oil to enter the Overrun piston apply area.
With that being said, If your sure there is no cross leak in the drum due to the reasons above or other unforeseen reasons.....Means you have a cross leak somewhere else.
The Pump Cover is a unlikely spot, The Overrun feed is all by itself next to a pump bolt.
In D4, The Overruns are isolated from any kind of apply oil, D1/D2/D3 oil has to be present for the Overruns to apply, In D3, The 2-3 shift valve has to shift for the Overruns to apply...Meaning the trans has to be in 3rd gear for D3 oil to reach the Overruns. In D1/D2, The Overruns are applied directly by the Manual Valve.
However D4 oil & Overrun apply are next to each other in a few places in the Case passages, This kind of cross leak is usually visible on the Separator plate gaskets.
I did check that Sprag/input sun gear could overrun with the Forwards applied, and it could. I used a '97-later stamped steel forward piston, per the instructions from sonnax. Then used the supplied modified overrun piston. all the lip seals are good I have checked many times now lol. AS far as a cross leak, that is what I think I have But the separator plate does not show it. Where ever it is it has to be close to the forward clutch circuit. because I feel like the overrun is applying the whole time the forward clutch is. The only place I can see they come close is the 3-4 input shaft.
Last edited by gearhead_i_am; Nov 22, 2015 at 12:01 PM.