hard shift when hot......

[421racing]

Hello everyone, I am new to this forum and here is my "icebreaker" thread!

I have a '99 tahoe and it has 137K on it. Whenever I drive it for more than 30 minutes or so in hot weather, shifting in the low gears(1-3) seems to be delayed, and when it does finally shift to the next gear it is not a smooth shift.....it "jumps" into the next gear....this only seems to happen in the summer months (I live in Vegas)...Once the weather cools down, I don't notice it until it gets hot again!This has happened to me for the past two summers....It does not occur when I drive short trips, only those lasting more than approx. 30 minutes ....

I have been told by more than one person that I am "lucky" that I got 110K out of this tranny, and I know that I will need to rehaul it soon, but I was wondering if this may be a problem that I could remedy without a rebuild.....

any advice would be appreciated.....

 

[bparker]

Sounds to me like the clutches are worn out and need to be replaced. :skep:

 

[marinekilz]

It could be a million things, from a line pressure problem to the sensors monitoring the line pressure in different areas (like thottle pressure and governer pressure) to the clutches and accumlator. Could just be a band in the tranny. I haven't look at the schematic for your tranny so I am speaking in general. scan tools will tell you what is engaging and when in the tranny to see what it is doing it, but if it does it in ALL GEARS then it is something commoning between the all.

 

[johnebgoode]

Considering the mileage it may be time for a rebuild. I would highly recommend an after market tranny cooler, if you dont have one already.
What color is the fluid. Is it dark or light as it should be.
Does it smell like it burning?

 

[RonH]

That shifting condition is called a "1-2 bump". It's possibly related to the control valve body of the transmission. Is your service engine light on? You may also be getting a "P1870 - transmission component slippage" code. GM has a service bulletin on it (TSB #010730023B).

The heating problem can be caused by your torque converter going and overheating the transmission fluid after heavy or long useage.

The transmission will eventually go out, and it will be at the most inconvenient time and place possible.

Mine started with the overheating and then came the bump, and then a thrust bearing went and destroyed the planetary gears. I was able to limp in on first and second gears. I got about 25,000 miles out of it after the symptoms started by never driving over 65, but I wouldn't count on it.

When you do get your overhaul, It's worth your time to shop around. I just got one done, a complete overhaul with a new torque converter, and all labor for $900.

 

[Redwood]

Same problem...

Dude, I had the same problem in my 95 yukon. We were in heavy traffic after a long fast run on the highway, trying to catch a flight for a family vacation to see gramma. The same shift problem had me worried. We made it to the airport and ran for it. All that week on vacation I thought about the return. Every thing was fine, all 250 miles of it. Service the tranny, it may last for another year, mine did. Good luck.