Transmission Overheating

i have a 2009 gmc 1/2 extended cab. 5.3 3.73
had it since 2009. on first trip to bakersfield, 107 outside. engine temp 204, tranny temp 243. i called Mataga in stockton, and they assured me that was fine. i have had it in the shop for the tranny but they still say it is fine. many time the truck will jump, but still they say it is fine. 4 time when going uphill with trailer, when i come to a turn, as i slow down it won't go around the corner without a full stop. Again Mataga says this is all normal, and they do not see any problems. what i do hear is you do have a extended warranty. my next truck will not be a GMC.
TT 2006 trailblazer loaded is 6100

Glad you caught it when you did. Most of the time it happens when you are 100's of mi away from home.

BenK wrote:

ralphnjoann wrote:

BenK wrote:
Missing a few facts or information...

Did your tranny AFT temp gauge then stop going up once you turned off
the TC lock up switch?

Did the temp go down or stay where it was before turning off that switch?

It stopped going up when I turned it off and started going back down.

Confirms others comments that it is going...

Says the 'lock up' clutch is slipping, which is is NOT supposed to do

I'd have it rebuilt very soon...

Thanks everyone for your help. We had the transmission rebuilt by a classmate of my wife's who has owned his transmission rebuilding business for the last 35 years. We trust him completely. He showed the the old parts he replaced and explained the wear on each one of them. The torque converter was indeed ready to go so we saved ourselves much grief later on down the road. It was money well spent.

My 2000 F250 bit the dust @ 110,000. More than 1 mechanic said that is about the average life span.

ralphnjoann wrote:

BenK wrote:
Missing a few facts or information...

Did your tranny AFT temp gauge then stop going up once you turned off
the TC lock up switch?

Did the temp go down or stay where it was before turning off that switch?

It stopped going up when I turned it off and started going back down.

Confirms others comments that it is going...

Says the 'lock up' clutch is slipping, which is is NOT supposed to do

I'd have it rebuilt very soon...

BenK wrote:
Missing a few facts or information...

Did your tranny AFT temp gauge then stop going up once you turned off
the TC lock up switch?

Did the temp go down or stay where it was before turning off that switch?

It stopped going up when I turned it off and started going back down.

diazr2 wrote:

carringb wrote:
TC-clutch is slipping. You are on borrowed time. Consider yourself lucky because most E4ODs did not make it as far as yours.

Yep I got 75K out of mine before it went to transmission heaven...

80k

If that is the original transmission.... I think it is telling you it is about done.
If the switch locking the TC is causing heat, stop using it.

I had to rebuild the transmission on my 996 F-250 psd diesel at 120,000 miles and then that went out at 165,000 and I put a Ford rebuilt transmission in the truck. It was working good when I traded it off when it had 205,000.

I got 167K out of mine and it was fine when I passed it on to the next owner.

On my 99 a TC lock up switch would have been useless. The TC stayed locked until some really slow speed, I can't remember what, maybe 40 mph in third gear on deceleration.

Even on pulling grades it would lock up in the lower gear it shifted to.