Headlines

4L80E Problems

old377guy

old377guy

Charter Member
Hey guys, I've searched all over the web and gotten some partial answers. The 4L80E transmission in my 1994 K3500 dually lost reverse suddenly. All forward gears seem to work ok. Fluid level, color and smell are good. No codes are set for transmission or engine and these were read at idle and at 25mph. I ran the 25mph in 1st gear test and there is no compression braking. I really need to find the inexpensive fix as the Mrs. and I are both "between" jobs. Does anyone have specific info about the band anchor pins, servo, solenoid or whatever gets me back on the road? Thanks for any enlightenment on this. - Jeff
 
I wonder if the 3 inch straight pipe exhaust, ported heads, intake and air box, OH and the injection control pump turned up 30% had anything to do with it???
Forgot the wastgate is set for 16PSI also.
 
Tinkerer said:
I wonder if the 3 inch straight pipe exhaust, ported heads, intake and air box, OH and the injection control pump turned up 30% had anything to do with it???
Forgot the wastgate is set for 16PSI also.
Click to expand...

I dont think so, loosing a lot of tourge because of the 3 inch straight pipe !

BTW, there is a 4L80E on the bay for cheap and low miles !
 
old377guy said:
Hey guys, I've searched all over the web and gotten some partial answers. The 4L80E transmission in my 1994 K3500 dually lost reverse suddenly. All forward gears seem to work ok. Fluid level, color and smell are good. No codes are set for transmission or engine and these were read at idle and at 25mph. I ran the 25mph in 1st gear test and there is no compression braking. I really need to find the inexpensive fix as the Mrs. and I are both "between" jobs. Does anyone have specific info about the band anchor pins, servo, solenoid or whatever gets me back on the road? Thanks for any enlightenment on this. - Jeff
Click to expand...

been a chevy trans tech for 26 years now....1994 is the early model 4L80E,,no selenoid or anything ecm controlled or electrical will cause you not to have reverse,one of 3 things happend ,,servo piston broke....reverse band broke,,or the reverse band anchor pins broke,,must drop the valve body to inspect servo piston and replace if broken,,if pins broke you will need a new case,,if band broke you will need to replace band and would be a good time to overhaul the trans while apart...sorry but no quick fix for this one
 
Last edited:
boatnt said:
been a chevy trans tech for 26 years now....1994 is the early model 4L80E,,no selenoid or anything ecm controlled or electrical will cause you not to have reverse,one of 3 things happend ,,servo piston broke....reverse band broke,,or the reverse band anchor pins broke,,must drop the valve body to inspect servo piston and replace if broken,,if pins broke you will need a new case,,if band broke you will need to replace band and would be a good time to overhaul the trans while apart...sorry but no quick fix for this one
Click to expand...

Thank you, I really appreciate your straight forward analysis of my issue. One question at this point, is the servo piston in the cylindrical housing with size bolts? Thanks again. - Jeff
 
I am in the process of rebuilding mine out of my 93 motorhome. It is my first and I am learning as I go(yikes).

In my case the rubber o ring which seals the clutch pack to hold fluid pressure broke and smoked the reverse plates. One 50 cent o ring cost be a ton of hours and a couple hundred bucks for a rebuild kit.

I am only hoping this will be the only time I have to pull this tranny as it was a chore to get out. Mainly due to how low this 13k lb beast sits and how hard it was to get in the air.
 
Underdog88 said:
I am in the process of rebuilding mine out of my 93 motorhome. It is my first and I am learning as I go(yikes).

In my case the rubber o ring which seals the clutch pack to hold fluid pressure broke and smoked the reverse plates. One 50 cent o ring cost be a ton of hours and a couple hundred bucks for a rebuild kit.

I am only hoping this will be the only time I have to pull this tranny as it was a chore to get out. Mainly due to how low this 13k lb beast sits and how hard it was to get in the air.
Click to expand...

make sure you air check the unit before you install the valve body.
 
boatnt said:
been a chevy trans tech for 26 years now....1994 is the early model 4L80E,,no selenoid or anything ecm controlled or electrical will cause you not to have reverse,one of 3 things happend ,,servo piston broke....reverse band broke,,or the reverse band anchor pins broke,,must drop the valve body to inspect servo piston and replace if broken,,if pins broke you will need a new case,,if band broke you will need to replace band and would be a good time to overhaul the trans while apart...sorry but no quick fix for this one
Click to expand...

boatnt, I sent a PM over to you but you may not have received it so I'd like to bring you up to date. I removed the valve body and gained access to the servo piston housing. I removed the housing and the piston. Although I don't really know what it should look like, it seemed OK. I've seen people refer to the rod or pin on the top of the piston as being too short and having to lengthen it. Any thoughts on this? Also I think that I may have dropped a few of the ball bearings form the valve body as there are only 7 left and it looks like there are spots for 2 more - any thoughts? Thanks for any help you can send my way. Jeff 503-975-0551
 
You must log in or register to reply here.
Back
Top