92 Yukon 4L60 Factory / Dealer replaced / Died on Highway ???

[TerryKing]

Hi Everyone,

About 6 months ago the AT on my 92 Yukon (140,000 miles) died. I decide to keep the truck and I installed a new GM Crate 350 which runs great.

I had the dealer install a new transmission (Like $3K total) with 12M 12,000Miles warranty. They replaced cooler lines (I have a new radiator) and did a flush and test on that.

Ran 100% normal for 3000+ miles, including about 1800 mile trip with 3000 lb camper.

3 days ago, started another trip with the camper, checked everything, ran great 180 miles and then suddenly the 1-2 shift didn't happen until high RPM (like 2000 to 3000) but seemed OK in 3 and normal shift to 4th/OD. Then 50miles later it slipped, ran in 3rd and then REALLY slipped and stranded me. Just got off Route 95 :-(

So towed to Union NJ Buick/GMC dealer who finally pulled the tranny and said it must be replaced.. "There's metal all over the inside". They have a replacement coming in tomorrow and are running the flush/test of the cooler.

Dealer guy said "this only happens from overheating".. Hmmm. Ran pretty level and easy. 35 degree weather. I have a gauge on the radiator OUTlet which did not rise and was about 170.

I put the original $$ into this to get reliability. Original trans ran 140,000 miles.

I'd like your opinions on What Happened Here... Did something internal just break, and then metal parts killed it? Could it have been overheating?? Why?? How??

Hope to be back on the road tomorrow, but I sure would like ideas on What happened, and what to look for for the future...

Thanks!

Terry King ...On the road from Vermont to Florida...
terry at terryking dot us

 

[rhino]

Unfortunately buying a "new" transmission from the Chevrolet dealership is only a bone stock build. They outsource their re-manufacturing and what you get is a good, stock, dyno tested transmission. They aren't able to do any upgrades. They are very overpriced for what you get. The nationwide warranty is mostly where the price is and is handy for someone who travels a good bit. It sounds like your 3/4 clutches got smoked. Without tearing it down it would be hard to tell really.

 

[1997chevydriver]

Well having your Trans gauge on the line coming out of the rad back to the Trans is not a good place to have it....... Best place is the pressure test port on the side of the Trans, next best is output line grom trans to radiator

 

[someotherguy]

Well having your Trans gauge on the line coming out of the rad back to the Trans is not a good place to have it....... Best place is the pressure test port on the side of the Trans, next best is output line grom trans to radiator

Lots of debate about this and your reply (and mine) will probably start it up again but I agree with you; that's exactly where I install them. Seems to be an accurate location to read the temperature based on my testing with an IR gun all over the pan, case, etc. after some hard runs - maybe a 1° difference at best as to what the gauge read! Also, T'ing in on a cooling line is another potential leak or place for the line to come loose.

Good luck with the warranty on it...as said earlier that's what you paid the GM price for, so hopefully they will stand behind it.

Richard

 

[TerryKing]

It sounds like your 3/4 clutches got smoked. Without tearing it down it would be hard to tell really.

Thanks for the responses, all! What would have caused the "1-2 shift delayed until 2-3000 rpm" symptom??

Maybe:

- Something / some bearing broke, metal fragments in system
- Pump?? Pressure?? Flow is low, so shift delayed???
- Low flow causes overheating, burns clutches??

Sorry, I don't understand the guts of these transmissions...

IF I did SomeThingWrong (Sounds like a Beatles song..) What could it have been??

Thanks, guys ... makes me feel less alone out here...

 

[1997chevydriver]

I'm almost wondering if they didn't adjust the TV cable (detent cable, kickdown cable, etc....depending on who writes the info) correctly.....

 

[bluex]

I'm almost wondering if they didn't adjust the TV cable (detent cable, kickdown cable, etc....depending on who writes the info) correctly.....

That or it moved or stretched. That would cause a late shift...

 

[rhino]

When a 700R4 gets metal and debris floating around it goes straight to the throttle valve. That's the valve the detent cable works. My guess would be either the converter went out, or anything really that could put out metal. Then it stopped up the throttle valve, which in turn caused low pressure, which led to clutch burnout. A stock converter on a 92 has a paper clutch vs the improved woven graphite and carbon clutches made after 95. Usually when a transmission looks overheated that's where the slipping is coming from.

 

[TerryKing]

Hi Everyone,

Happy to say Dealer replaced with new 4L60 from factory $00.00 cost to me. WHEW!!

I had a nice 1/2 hour talk offline with their 25 year transmission guy. He said he usually can figure cause-effect on transmission problems, but not on this one. It was a 3000 mile GM rebuilt and nothing happened that should have caused a problem. Seems like something was not caught/replaced in the GM rebuild.

AND here's the interesting thing:The truck runs much better! Now it's apparent that the previous transmission had some kind of internal friction or dragging.. It now takes less throttle for the same speed and MPG is about 15% better. The 1-2 shift is nicely placed and smooth without hesitation.

I ran 500 miles in D with 3000 lb trailer and it was an easy run. Now around town no trailer it seems just simple and nice.

Wish I had some overall diagnostic to check this all out other than my personal perception.

Anyway: Back On The Road to Miami and Snowless Places...

Thanks for all the help and perspective!

 

[rhino]

Awesome news!!!