4L60E transmisson problems!

kylebigbucks · May 31, 2003

I Have a 98 GMC seirra with the 350 vortec and 4L60E transmission 118,000 miles on the truck....the tranny and engine suck in this thing and I am getting very very frusterated. I bought it only about 7,000 miles ago hoping for the best. Read the pathetic details on my engine on a different post to this board.

This last week the tranny stared shifting very hard. When I shut it off and restarted it it ran normally again for a period of time and then start shifting hard again. And it contiues on the same cycle....

Long story short I brought it in to the dealership and they said something to the effect of a computer running diagnostic code checks the tranny every so often for problems, when it finds a problem it adjusts the pressure etc. If the problem is bad it will over adjust and that is why it was shifting so hard. When the computer ran its test it found something not right and adjusted for it causing the tranny to shift hard, when I shut off the engine it reset the computer and it ran normal until the computer did anouther test.

The mechanics took off the pan on the tranny and inspected it for metal filings...they found a lot apparenlty and said that I should either get a new valve body, rebuild the trasnmission, or get a rebuilt tranny.

I had the tranny fluid changed when I bought it and and it looks good and smells normal. I had these problems when I was delivering mail with the truck last week ( a ton of stop and go driving) and have since driven 50 highway miles with no problems at all. It seems to run normally, at least i noticed no change as complared to when I bought it and I was pulling a 17' fishing boat for those 50 miles.

I am leaning toward getting a gm goodwrench tranny put in but would like to delay it as long as possible, at the same time I don't want to have to worry about the tranny stranding me somewhere.

Does anyone have any experience or advice for this problem?

Also, the boat I pull with this truck is about +/-2000lbs, is it okay to pull it in OD if it seems to pull good? I can hardly even tell I am pulling anything.

robsawatsky · June 2, 2003

It is likely the computer is detecting too much slippage in the transmission. It then compensates by setting the pressure to maximum for all shifts. This is what causes the hard shifts. It keeps the tranny from burning itself up in the short term, but is obviously something that needs repair. There are also possible other electro-mechanical faults that can cause this, but internal wear or damage is most likely.

COZWV · June 7, 2003

Well my truck (2000 Silverado 6.0) has been in the Trans shop for 8 weeks with that exact problem. The trans has been rebuilt, two different torques tried, two different valve bodies, computer.

The shop owner is so mad. This is my company truck and he wants our business. It embarrassing him bad.

We have other trucks that are doing this. I've also read of this problem lots of times but never any real answer. One truck only does it occasionaly but mine does it always after driving a few miles (especially on the interstate) They thought they had it fixed and they were driving it back to our office and "BANG" slam shifting again!

It really sucks because I think GM knows whats wrong but wont say because this trans is in so many of their vehicles.

Race18 · June 9, 2003

I had my tranny explode with 77,000 miles. Took it to AAMACO and they had 5 others the same year model with the same problems. The showed me the weak link in these trannys. I had them completely rebuild everything with new parts. $3000.00 later it ran fine for 25,000 miles then the torque converter started shuddering. I took it back and they replaced it and said I needed a valve body upgrade. They did that free of charge of course. I shift a touch hard at times but all is fine so far. These trannys suck and GM should replace them with the 4L80E. Just my 2 cents.

COZWV · June 13, 2003

By the way mine is a 4L80E, Also the other truck at work is a 4L80E also (Both 3/4 tons)

Just talked to the Trans shop, They think they may have a fix. He mentioned earlier about putting some kind of resistor on it from Radio Shack! Dont know yet. It has to be electronic. As my previous post shows all of the hydraulic end of it has been rebuilt.

I've also seen a TSB dealing with the Alternator causing a problem with the trans.

I WILL DEFINATELY LET EVERYONE KNOW HOW THEY FIXED IT!

COZWV · June 20, 2003

OK, Where now going to try a new transmission body! The trans shop has exhausted every other means! This is the only thing he has left!

By the way his original price of around $1,400.00 to rebuild it is still the same. He has absorbed all of the cost of trying so many things. Plus he has had it another shop and at a GM Dealer along with my company having the valve body replaced at a GM Dealer prior to the trans shop getting it.

This has been a nightmare!

MCourson · June 20, 2003

Also, the boat I pull with this truck is about +/-2000lbs, is it okay to pull it in OD if it seems to pull good? I can hardly even tell I am pulling anything.

On my '94 w/ 4L60E there is a sticker in the door jamb that says do not tow in OD.

Hope you get it all worked out

kylebigbucks · June 21, 2003

Well, I ended up putting a rebuilt gm goodwrench tranny in, (another 4L60e with the latest upgrrades). It was $2200 when it was all said and done but you also get a 3yr/50k warranty with it, which is pretty hard to beat.

I put some amsoil ATF in it right off the bat. I am not overly impressed with the way it shifts for a remanufactured tranny. Not very smooth and seankess, in fact I am not sure zI can really tell the differnce between how the new tranny shifts and how the old tranny shifted when the code was reset. But that might have something to do with the synthetic ATF.