'01 2500hd Transmission

Anonymous-0 · Dec 18, 2009

Posting for friend. 01' 2500hd 6.0L 4l80E 70K.
Trans cooler line popped off while driving. Friend didnt notice until engine revved out and stalled. Claims it was 2.5 qts low. But now truck will not move when in gear. Never any transmission problems before this. Also cannot find Trans fuse. Any Ideas?

Brokenwrench · Dec 18, 2009

A no move on a 4L80E won"t be electrical. GM has had alot of trouble with the clips for the cooler lines breaking at the cooler.

My guess would be that if he blew a line and drove til it started slipping, he lost alot more than 2.5 quarts. They can easily pump out 5-7 qts before the pump starts cavitating. 2.5 qts shouldn"t really be enough to slip the trans. Even if it ran low enough to damage the internals, once you get the fluid back up to full, it should at least move.

I have seen em where they have been run low enough to score up the pump. Then they will howl and have a delayed engagement. Usually you can replace the clips, fill it back up, and off you go.

Brian Jasper co. Ia · Dec 18, 2009

Time for a rebuild. The forward clutch is surely fried. The pumps in an 80 are the internal gear type. GM hasn't had any "clip" issue. The only trouble I've seen is the cooler lines on trucks with the Allison trans weren't crimped well and cold weather makes them leak.

Brokenwrench · Dec 18, 2009

Hello Brian,

I agree that baked forwards are very likely. Just seems odd to blow a cooler line and only add 2.5 qts.

The clips I"m refering to are the retainer clips GM uses in the later cooler line fittings. Those thin little E shaped wire clips.

I haven"t seen any trouble with them breaking at the transmission end, but have seen quite a few broken clips on the radiator side. I think line vibration plays a part. When the clip breaks, the line will blow off. Havent seen any trouble on the allisons, or the 4L60Es come to think of it. I had 4 2500/HDs in this fall with blown lines. Every one, we"d find a piece of the broken clip somewhere, and I think all were the top line on the rad. The clips look just like they were sanded thinner and thinner, til they just fell apart. Now, every one gets new clips, regardless.

Have you seen any solution to the drooling allison crimp connections? Seems I can put new OEM lines on and they might or might not leak. I have actually thought of taking new sets of lines up to the local parts house and having them recrimp them in their hyd hose crimper.

Anonymous-0 · Dec 19, 2009

i had to put a new set on my allison around 70000 miles. think a new set was around 200 bucks. RICK

bradk · Dec 19, 2009

I can guarantee the tranny blew out more than 2.5 qts.The entire tranny holds about 16qts.Dropping the pan alone will yield about 7.More likely,like Brokenwrench says, 5-7 was lost.

Silly question,but he is running the truck in park at idle when he checks it,right? The 4L80-E trannys are pretty dang tough and usually come around again when full of fluid.

The only clip issues I've seen are the ones that pop out from not being properly installed.Usually after a tranny flush or line replacement.

'01 2500hd Transmission

Anonymous-0

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Brian Jasper co. Ia

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Brokenwrench

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Anonymous-0

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bradk

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