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I finally fired up my l33/4l80e swap. Fluid level looks good(measured dipstick against pan rail). When I put the car in reverse, it almost feels like the brake is on or something. No hesitation in any forward gears. I will look tonight to make sure there are no other unrelated issues. Does this sound like anything common?
I will have to throw a pressure transducer on there to read pressure.
To be clear, if I raise the rpm to about 2000, it will move in reverse but will stop as soon as I get off the gas. That is what I meant about it almost feeling like the brake is on.
Reverse is a manually selected gear. Line pressure is supplied to the manual valve which turns into/supplies reverse, PRN, PRND43 & PRND4 oil. The line pressure for reverse is raised by the reverse boost valve/PR system. The computer only controls the pressure control solenoid partially. The shift solenoids are in 1-2 off 2-3 on for P/N, R & 1st. if you follow the reverse only circuit. A stuck #7 check-ball in the VB (that's supposed to block low oil) would supply reverse & low oil, that oil could be feeding the forward clutch.
If it was me, I would pull the VB and check it over for correct location of VB gaskets, check *****
I attached some pages from my GM 4L80E tech guide for reverse, m1, check-ball function & apply chart. I hope it helps.
It's too late to start the car, but I did check something. With the car off, I put it in reverse and tried to push it backwards and it wouldn't budge like the brakes were on or something. I also put it in neutral and experienced the same thing. Now I'm thinking it might be something related to the emergency brake rather than a transmission issue. Or, does that sound consistent with a transmission issue as well?
No matter what gear you select with the engine off, there is no pressure to apply anything.
I would look into the brakes on the rear, maybe disconnect the drive shaft and see if it will roll then. The drive shaft should turn both directions in neutral. One direction will be more difficult to turn because the low roller will lock causing the gear-train to turn. If it doesn't turn one direction, it is probably internal to the transmission. I read through your build thread, sounds as if you took your time and set things up correctly.
Let us know...
Well, I unhooked the emergency brake completely and that made no difference. I also unhooked the driveshaft and I can't turn it at all in park, which is good. In every other gear, I can rotate the driveshaft forward but not in reverse. is there anything else I should be checking before I go ahead and pull the transmission?
Well, I unhooked the emergency brake completely and that made no difference. I also unhooked the driveshaft and I can't turn it at all in park, which is good. In every other gear, I can rotate the driveshaft forward but not in reverse. is there anything else I should be checking before I go ahead and pull the transmission?
was there any modifications to the intermediate band it self. Did you use a wide band in the pre 97 transmission you built? if you did the apply pin has different length. The longer pins are identifiable at a glance by a ring in the shaft. Longer pin required measures 2.720, Shorter pin is 2.532
Maybe loosen the VB and see if the drive shaft will now turn both ways...
was there any modifications to the intermediate band it self. Did you use a wide band in the pre 97 transmission you built? if you did the apply pin has different length. The longer pins are identifiable at a glance by a ring in the shaft. Longer pin required measures 2.720, Shorter pin is 2.532
Maybe loosen the VB and see if the drive shaft will now turn both ways...
I don't believe so, but I can definitely check. Could that cause the problem that I'm seeing? I can drop the pan and loosen the valve body to see if that makes a difference.
You just have to find the bind keeping the output shaft from turning both way's... If there were no modifications to the intermediate band (M2) and/or the servo.
My guess will be the 4th clutch or the overrun has one clutch bound up when you assembled it.
Did you put the input shaft/overrun drum in with the 4th clutches in place?
Or did you install the input shaft/overrun drum first and the 4th clutches after?
When you install the input shaft/overrun drum with the 4th clutches in place you have to jiggle/rotate the shaft to lug the clutch splines. This can allow an overrun clutch to fall off the hub. It's not much, I've done it myself...
If you have to take it out, just loosen the front pump and see if the output shaft spins then. You may have to take the pressure off the overdrive assembly by pulling the pump out 1/8".
Keep us posted...
OK, I made a little progress. I jacked the car up and put it on some wheel cribs and then dropped the pan and drained the fluid. The fluid appears to be in very good shape still which is one good thing. After that, I loosened all the bolts in the valve body so that it hung down about a quarter of an inch. With that loosened, I can now turn the driveshaft in both directions.
Make sure you didn’t accidentally use a longer accumulator bolt in place of one of the bolts that goes in the valve body and secures it to the case. If you did, it can make contact with the band. Seen someone that accidentally did that before using incorrect bolt in one of the manifold pressure switch holes and had a similar issue to yours. Is the 3/4 accumulator deleted?
Last edited by 5.7stroker; Nov 13, 2022 at 02:33 PM.
Make sure you didn’t accidentally use a longer accumulator bolt in place of one of the bolts that goes in the valve body. If you did, it can make contact with the band. Seen someone that accidentally did that before using incorrect bolt in one of the PWM holes and had a similar issue to yours. Is the 3/4 accumulator deleted?
I'll have to check. They are all just loosened right now. Where would I have to have a longer bolt for it to be an issue?
Through the pressure manifold switch if I recall correctly. The fact that as soon as you drop the VB and it starts rotating makes me wonder if maybe one of the longer stock accumulator bolts (which are of course omitted in favor of the smaller 3/4 accumulator block off plate bolts) may have been accidentally used to secure the PMS and be making contact with the band.
Through the pressure manifold switch if I recall correctly. The fact that as soon as you drop the VB and it starts rotating makes me wonder if maybe one of the longer stock accumulator bolts (which are of course omitted in favor of the smaller 3/4 accumulator block off plate bolts) may have been accidentally used to secure the PMS and be making contact with the band.
OK guys, I think we might be onto something. I pulled the six bolts that hold on the pressure manifold switch that all have an 8 mm head. Three were longer and three were shorter. Are these all supposed to be the same size? Just for kicks, I left out the six bolts for the pressure manifold switch and snugged up all of the remaining 10 mm valve body bolts and the driveshaft still turns both ways freely. What do you guys think? Is this my issue? If so, where is a good place to find three of the shorter bolts since I have no idea where the old ones are now.
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4l80e reverse issue 
