1999 GMC Transmission Problem

[Mr.890]

When driving my 1999 GMC Denali for an extended period of time, say 30 miles or more, it begins to shift hard when accelerating. It will eventually turn on the SES light.

When I turn the truck off, even for just a minute or two, it will shift fine until I take another extended trip @ cruising speed (55-85 mph).

I have already had the transmission rebuilt. It didn't fix it.

Anyone know what is going on?

[Ernie22]

Sir,

I also have a 1999 Sierra Shortbed Pickup with a 5.3 liter engine, 4L60E
transmission w/overdrive, 3.73 rear end that special ordered. Ever sinse I bought it I have had a similar problem. Two days ago it went out in that it slips, shifts hard all this between 2-3 and 3-drive when I have the overdrive on. When I turn it off it operates better but still has a problem. I am going through the GMC service manuals to find the problem but no luck yet. If I find the problem I will let you know, please let me know if you can if you find out what's wrong. I believe it is a manufacturer problem and ther should have been a recall but that will be the day with GM.

Best of Luck and happy Holidays,
Ernie Ackerman
[email protected]

[Ernie22]

Mr.890,

I belong to ALLDATA and I looked up our problems and may have found some help. It seems GMC had a recall on both our problems. I am including 2 Winzip files for you to look at. I hope they help. If they don't I would suggest going to GMC service because there is alot of recalls or TSB on our transmission.
I assumed you a 4L60-E transmission but you might have the 4L8060-E but there are similar recalls and TSB's for both and we should have received a notice from GMC but I never did, I don't know about you though.

Best Regards,
Ernie22
[email protected]

Nick,

I just found out I cannot email you the attachments. Please send me your regular email address and I will send them to you.

You can always email me at ernie22.comcast if this does not help.

[Jeremy-WI]

Ernie22,

The reason no one has received a notice is because GM doesn't send notices to customers on TSB's only recalls. The purpose of the TSB is to give a heads up to service techs on the problem.

[Ernie22]

Jeremy,

I relize that. The point is from "my" experience GM does "not" even send out all of the recall notices, for what ever the reason. They are not always proactive nor consistant. I special ordered my truck, still have it and going to have it serviced I have found out there was recalls.

Ernie

[beuthling]

I have a gmc savana 96 3/4 ton After a 20 min drive or so when tranny gets hot , It shifts really rough. Is it broken, When I stop it and start it a gin it seems to work fine. It sets of a code for slipping tranny. Should I put a cooler on it?