Transmission Problem [Archive] - GrandAmGT.com Forum

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bigtard
02-25-2006, 03:05 AM
My 1999 GAGT with about 99,000 miles has a transmission problem that I need to fix.

The transmission often severely slips.

But it ONLY happens under these conditions:

(1) The outside temperature is above about 65 degrees.
(2) The car is driven for a while.
(3) The car is taken out of drive and put back into drive (e.g. after filling up at a gas station).

I've driven 500 miles at almost 100mph stopping only to get gas when it was 45 or 50 degrees outside. No problems. None. I've done city driving when it's below about 65 degrees. No problems. None.

But once the temperature creeps up above about 65 degrees, I start have big problems seemingly regardless of distance as long as I've driving maybe 5 miles or so.

Has anyone else had this problem? Do you know how to fix it?

I have taken my care to mechanics and dealerships. Those shady morons just check the oil, notice it's fine and has no debris in it, and then try to sell me a new transmisson.

H.O. Driver
02-25-2006, 06:34 AM
I have taken my care to mechanics and dealerships. Those shady morons just check the oil, notice it's fine and has no debris in it, and then try to sell me a new transmisson.
Thats because its easier for them to swap the trans then it is to pull it, rebuild it, and put it back in. Have you had anywork done to the trans? Fluid/filter change lately? It sounds like synthetic fluid was put in, and once it warms up enough, its too slippery for the clutches. (I have seen that happen on a few FWD GM ATX that switched to a full synthetic blend)

Thats my theory, but could be wrong. The transmission has 99k on it, right? If so, thats a pretty good life for the stock 4t45e.

bigtard
02-25-2006, 07:57 PM
Thats because its easier for them to swap the trans then it is to pull it, rebuild it, and put it back in.
It's more profitable.

Have you had anywork done to the trans? Fluid/filter change lately?
All that was done about 4000 miles ago.

It sounds like synthetic fluid was put in, and once it warms up enough, its too slippery for the clutches. (I have seen that happen on a few FWD GM ATX that switched to a full synthetic blend)

So why does it only do it when it's warm outside? Doesn't a transmission get hot after driving several hundred miles when it's, say, 50 degrees outside?

I'm having a hard time believing that my transmission would get nice and toasty after, for example, 10 miles when it's 80 degrees outside but it doesn't get nice and toasty after extensive driving when it's 50 or 60 outside.

H.O. Driver
02-25-2006, 11:23 PM
the outside air will cool the trans fluid specially when moving. Here in Michigan, the trans never gets above 115* in the city when its less then 40* outside and I don't have a trans cooler. When its 70* or higher, it takes no time to get to 180*.

If it was the 1st time the fluid was changed 4k ago, thats kind of what did it. If the stock fluid has been in that long, the gunk and sludge is what was holding it together :(

GAGT7386
02-26-2006, 02:40 PM
The 4t45E is a good tranny ... as long as the usual maintance is kept on it. When you say it was done 4000 miles ago was it a flush or just a pan drop and refil? With that many miles on it you should have only done a pan drop, after so many miles if the tranny wasn't well maintaned then a flush does more bad then good. It losens all the dirt and crap in there ...

bigtard
02-26-2006, 11:33 PM
If it was the 1st time the fluid was changed 4k ago, thats kind of what did it. If the stock fluid has been in that long, the gunk and sludge is what was holding it together :(

You misunderstand. The problem existed before the oil was changed. The problem was there after the oil was changed. I had the transmission checked because there was a problem.

bigtard
02-26-2006, 11:37 PM
When you say it was done 4000 miles ago was it a flush or just a pan drop and refil?

I don't know. It was done while I was away in Los Angeles. The charge was about $60, if that helps.

...after so many miles if the tranny wasn't well maintaned then a flush does more bad then good. It losens all the dirt and crap in there ...

Either way, the problem was there before they looked at it and it's still there. The only relevant variable seems to be the outside temperature.

bigtard
02-26-2006, 11:38 PM
Here in Michigan, the trans never gets above 115* in the city when its less then 40* outside and I don't have a trans cooler. When its 70* or higher, it takes no time to get to 180*.

How do you know that? Do you have some sort of aftermarket sensor?

H.O. Driver
02-27-2006, 07:25 AM
How do you know that? Do you have some sort of aftermarket sensor?
yes, I have a trans temp gauge in the a-pillar pod. Also if you have a tech II or a scanning device, the trans fluid temp is also shown in the PCM.

Is the funny shifting on the 1-2 shift only or all shifts? The 99 and some 2000 model years have a bad (read, too small of a ) cylinoid and it can't hold enough line pressure for the 1-2 shift to be firm. I know my car has it, I have just maxed the line pressure in the trans, and once it learns the shift points it goes away. I highly doubt thats what you wanna do though, its just a band aid, not a fix. It only keeps it happening till it finally becomes a failure in the end.

bigtard
02-27-2006, 01:05 PM
Also if you have a tech II or a scanning device, the trans fluid temp is also shown in the PCM.

Unfortunately, I don't.

Is the funny shifting on the 1-2 shift only or all shifts?

It's not even the 1-2 shift. When I initially start the car, it shifts perfectly. No problems. The problems happen when I shift out of drive into park, reverse, or neutral and then later shift back into drive. The slipping happens during that initial engagement into first. Once it's in gear, there are no problems at all until I shift out of drive again. As long as the car stays in gear, it's fine. For instance, I can stop at lights and take off again with no problem. I can cruise around Phoenix in 115 degree heat, and there's no problem until I shift out of drive.

bigtard
02-28-2006, 12:00 PM
P.S. Is there any chance my problem is related to this http://www.grandamgt.com/forum/showthread.php?p=760851#post760851 ?