Got a question 'bout a GM Tranny

[silverlion]

I am considering getting a 1993 3/4 ton Suburban w 454. It has an issue with shifting. I don't think it's the tranny though. The PO said it drove fine for 30 mins or longer before it acted like it went to neutral. He would pull over and turn the rig off, turn it back on and it shifted fine. He bought another tranny and installed it to find that it did the same thing. Sounds electronic and on the truck, not the tranny. Cruise control maybe? The tranny is a 4L80E so its not the POS 4L60E. I can get it cheap and the rest of the rig is in top shape.

Thought I'd ask. Maybe someone here knows someone that knows someone that knows something.

Thanks ahead of time. Best of all, I get to keep my Pathy!!!!!

Edited March 27, 2009 by silverlion

[Kingman]

The 4L80E is an amazing transmission, butthe 4L60E is the same but without overdrive. They are electronically controlled transmissions, so it's a sensor or something glitching out.

 

Have you driven it yet?

I don't know how someone can "think" it went in to neutral. Did it suddenly kick out of gear and rev high? Was it during a shift, or in gear and cruising? Which gear?

 

Just him saying it's acting like it's going into neutral isn't enough information.

However, if he put a new transmission in it, then it is something on the truck. Plain and simple.

 

The 4L60E I had in my 2500 Suburban would sometimes come out of second and back into first when it was cold a few times if you were driving very slow, but once it got a little warmer it went away.

Edited March 27, 2009 by Kingman

[silverlion]

I was wondering if they have a spped sensor. I know on some electronic trannies, the circuts were all tied in together through the cruise control via a speed sensor. Just though I'd throw that in there. The 4L80E is a virtually bulletproof tranny. And to have 2 with the same issue...very unlikely. If it's a speed sensor, that's a 30dollar part... May be worth a shot. Hell I can always part the truck out and make a profit.

[vengeful]

How cheap are we talking here?

 

Could be the trans control module, too.

[silverlion]

1000 bux. The truck as a whole is in real good shape. Engine is strong, 4wd works, a few scratches, but the interior is cherry, the carpet could use a shampoo in the cargo area.

[5523Pathfinder]

Found this on Alldata...

 

 

 

DATE: 1996

 

TECHNICAL BULLETIN # 333

 

TRANSMISSION: 4L80-E

 

SUBJECT: Neutrals on the 3-4 upshift

 

APPLICATION: GM Trucks

 

4L80-E

 

 

 

 

 

 

 

This symptom may be caused by a leak in the solenoid B circuit. It is not uncommon for the feed circuit for shift solenoid B to supply too little oil. When this happens, and solenoid A closes for the shift to fourth, solenoid B pressure can not continue to hold the 1-2 shift valve in the shifted position. The transmission is actually making a 1-2-3-1 shift which feels like neutral.

 

Note :Because the computer still commands fourth gear when the manual lever is in manual third, this condition will still occur in manual third.

 

If the leak cannot be found (damaged solenoid B o-ring, solenoid B doesn't close fully when energized, etc.) drill the shift solenoid B feed orifice to .035"-.041".

 

 

I will look for more.....

[shift220]

First of all, the 4L60E isn't a POS and can't be compared to the 4L80E since they are two very different animals.

 

The 4L60E has overdrive just like the 4L80E, the 80 is just a lot bigger in size and is rated for more torque. It is meant for heavier/higher horsepower trucks.

 

It does sound like a problem with the computer. I'm not sure with 93's but on newer trucks the ECM controls the transmission. I'd look into replacing that first if it isn't throwing any codes.

[silverlion]

Yeah, no codes at all. I think I might just buy the thing and do a little work to it. If I can't get it fixed, I'll re sell it or part it out. Thanks for the help. It does just as the TSB states. Sounds like a cheap fix. Thanks a bunch everyone. Best of all, I get to keep my Pathy. Time to celebrate with beer and some BACON!