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Discussion Starter · #1 ·
I've got a 1992 chevy 2500 4x4 6.5TD/4L80E 3.42 gear The trans shifts great in all forward gears, no codes, and locks up the torque converter as it should. no slipping whatsoever. When put in reverse it clunks like its engaging, then won't move, no sign of moving. It clunks like its in, but 100% freewheels. Any chance its something stupid and easy??
 

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Discussion Starter · #3 ·
Well my Dad traded this truck in and its been sitting for about 6 months like that. I'm gonna buy and I'm tryin to figure out if it really needs a trans. It will manually go into first. checked fluid again to make sure, was a little low, but I filled it and still the same. Still clunks like its in reverse but no movement.
 

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First off it takes twice or more pressure to have reverse gear than the forward gears. Up to 310 or so.
It could be anything from low fluid level so check that first. A worn rear band. if it is not the rear band then place the shift selector into first gear manual and see if it will go forward. If it does then you just ruled out the rear band application.
It could be a worn reverse servo seal.

Deeper still is the direct clutch or overdrive roller clutch failure.
 

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Hello All,

I have read quite a few posts on no reverse and I am still not exactly sure what needs to be done.

The issue that I have is a little different. The truck was fine and I go to back out of a parking space and it goes in to reverse and will Idle slowing backwards. If you try give it some gas it does not go backward any faster. It will only idle backwards. It will not reverse up any slight grade.
I have the 4l80 and All forward gears work great.
The fluid is full, fresh red/pink, no burnt smell. The trans does leak fluid out of one of the seals. I am not sure when the filter was last changed.

Can anyone give me ideas as to what is wrong and if the solution is a complete rebuild or of something that can be done with the trans still in the truck.

the truck has 300,000 miles on it and this is the second trans, as the first one was destroyed by water ingestion in a FL hurricane. I am not sure how many miles are on this trans.
 

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Before you overhaul.....The rear servo adjustment is very sensitive to band wear. I have fixed many 4L80Es for this complaint by installing a slightly longer servo pin. This can be done in the vehicle and is a cheap fix.
Forward gear is not affected when the rear band does not hold.....only the braking/holding ability of manual low gear.

I will note here that if the rear band is completely trashed, this would not be a long term fix.
 

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Slick250:
I have a H1 Hummer with a 4l80 trans that has also lost reverse. It also will not hold back in first. I would be interested in a little more detail about installing a longer servo.
Thanks,
John
 

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Little more info about my tranny problem. When it went out it made a clunk sound then would not move. I had a shop check the linkage, fluid and check for broken wires and they didn't find anything. After reading some old posts it appears I may have a broken band, if that is the case can it be fixed with the tranny still in the truck?
Thanks again,
John
 

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This seems to be a fairly common failure point on the 4L80E. IMO whats happening is either that the band anchor point breaks or the band anchor bolt breaks. If it just all of the sudden won't go into reverse I highly doubt its because the band has worn or stretched and will no longer hold.

I know my 4L80E with a shift kit has a very very strong engagement into reverse. I think if my 4L80E does fail it will be the reverse band.
 

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Like I said before, band pin length is very sensitive in order for Manual 1st holding and reverse. Sometimes the pin needs to be longer than available from the OEM. I have welded 1/8th to 1/4" extra length on several units over the years and made them last a long time.
The band anchor on a 4l80e does not break. period.......however there are two anchor pins pressed in the case that CAN walk out a bit and cause the band to lose contact with them. (You can see this from the outside of the case towards the top.) That is not common though.
If you weld the pin, make sure to smooth it back up on the tip. If it still does not work, the band is broken and cannot be replaced without complete teardown.
 

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Please excuse my ignorance when it comes to Automatics, I am mechanically inclined but my truck is the only automatic that I have even owned.

Where is the reverse servo? (better yet what is the best manual that will show me the reverse servo?
 

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I'm going through this same problem and joined this forum just to look at the links and pictures of a 4L80E.
I'm real curious as to what Slick50 charges to do the reverse servo apply pin modification. I started to go after mine to discover the main valve body is just enough in the way that I could'nt get the servo cover off. Called every tranny shop in this one horse town and all said pretty much the same thing. The cost for that much tear down to get to the servo, might as well rebuild. The more knowledgeabe said it was more than likley the drive drum that broke based on my discription of the damaging event.
 

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Slick 250 Please...tell me more!!!!

Before you overhaul.....The rear servo adjustment is very sensitive to band wear. I have fixed many 4L80Es for this complaint by installing a slightly longer servo pin. This can be done in the vehicle and is a cheap fix.
Forward gear is not affected when the rear band does not hold.....only the braking/holding ability of manual low gear.

I will note here that if the rear band is completely trashed, this would not be a long term fix.
On a mildly chilly morning, my 95 c2500 6.5 TD (4L80E) reversed 2 feet and all of a sudden, felt like a fuse popped. No reverse now -not even a hint of reverse. All forward gears work perfectly.
The fluid was brown and low. I drained the pan, replaced the filter, filled it back up.
Still no reverse.
Drove it for about 3 miles, pan was leaking.
Dropped pan again.
Fluid was brown again -probably from residual fluid in torque converter.
Disposed contaminated fluid.
Sealed pan properly and refilled with fresh fluid.
Still no reverse.

Please give me hope that I haven't trashed the tranny! Seems a used one for this vehicle is impossible to find!

Of course, I have always avoided transmissions. Any info you can provide will probably be taken directly to my mechanic friend as I won't have a clue where to look for something like, "The rear servo".

Thanks for your help!

Ross
 

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Thanks Slick! -One more thing....

Like I said before, band pin length is very sensitive in order for Manual 1st holding and reverse. Sometimes the pin needs to be longer than available from the OEM. I have welded 1/8th to 1/4" extra length on several units over the years and made them last a long time.
The band anchor on a 4l80e does not break. period.......however there are two anchor pins pressed in the case that CAN walk out a bit and cause the band to lose contact with them. (You can see this from the outside of the case towards the top.) That is not common though.
If you weld the pin, make sure to smooth it back up on the tip. If it still does not work, the band is broken and cannot be replaced without complete teardown.
You mention "manual 1st holding" -I'm not sure what exactly that means. Does it mean you can put the gear shift in 1st and when you start driving, it will pop out of gear?

Hopefully, you're part of the crowd that lives by the statement, "there's no such thing as a stupid question". If not, pardon my stupidity!

Thanks again,
Ross
 

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Its not hard. Dump the fluid, drop the pan, and 5 bolts remove the servo cover/housing. Pull the servo out, take off the E ring and remove pin from servo, then put in new pin and reinstall.
 

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Its not hard. Dump the fluid, drop the pan, and 5 bolts remove the servo cover/housing. Pull the servo out, take off the E ring and remove pin from servo, then put in new pin and reinstall.
Hi, I have a 2003 Chevy express 3500
I lost reverse other gears works good
Will that solve my issues
Replace the servo pin? I ask a mechanic and he said that I have to get a new transmission just wondering before I buy. Whole new transmission
 

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Hi, I have a 2003 Chevy express 3500
I lost reverse other gears works good
Will that solve my issues
Replace the servo pin? I ask a mechanic and he said that I have to get a new transmission just wondering before I buy. Whole new transmission
Welcome to DieselPlace

Here is some info on the Servo Pin from the trans FAQ page: Question: - 1999 Suburban K2500 - No Reverse
 
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