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Discussion Starter · #1 · (Edited)
I have an 03 GMC 3/4 ton 4x4 with a duramax allison combo. About 60,000 miles ago My injectors went bad, and lunched my engine. I had a new duramax engine installed at the dealer and everything ran great until a couple of weeks ago. I was driving down the freeway when the trans started dumping fluid from the front of the bell housing. I pulled the transmission, checked the pump bolts and replaced the front seal. I found where the seal was riding on the converter was shiney, but there was no groove. I sanded the shaft a little to make sure the seal seated, and bolted everything back together. The dealership didnt line the tranny up correctly, and the alignment pin on the right side was pressed back into the bell housing. I drove the pin back into place, and bolted the tranny back in. The leak was still there, but not quite as bad. Almost as bad, but a little better.
I took the tranny back out and checked everything in the front. The pump bushing is coated in red, and I don't see any uneven wear patterns. I don't see any place that even looks like a crack either.

I bought an allison from a wrecked truck. It is an 05 3/4 ton 4x4 like mine with a gas motor. I cant figure out what is wrong with the tranny in my truck, and Im hoping this other allison will work.

Can anyone tell me if there are any differences between an 03 and 05 allison? Also if there is a difference between the allison in a gas engine truck and a diesel engine truck?

Thanks for your help!!
 

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Im no expert but I believe they are all the same, as long as the 05 tranny isnt a 6 speed. If its a 5 speed, everything should be the same I would think. Someone with better knowledge on this will hopefully chime in so here's a bump for you!
 

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I have an 03 GMC 3/4 ton 4x4 with a duramax allison combo. About 60,000 miles ago My injectors went bad, and lunched my engine. I had a new duramax engine installed at the dealer and everything ran great until a couple of weeks ago. I was driving down the freeway when the trans started dumping fluid from the front of the bell housing. I pulled the transmission, checked the pump bolts and replaced the front seal. I found where the seal was riding on the converter was shiney, but there was no groove. I sanded the shaft a little to make sure the seal seated, and bolted everything back together. The dealership didnt line the tranny up correctly, and the alignment pin on the right side was pressed back into the bell housing. I drove the pin back into place, and bolted the tranny back in. The leak was still there, but not quite as bad. Almost as bad, but a little better.
I took the tranny back out and checked everything in the front. The pump bushing is coated in red, and I don't see any uneven wear patterns. I don't see any place that even looks like a crack either.

I bought an allison from a wrecked truck. It is an 05 3/4 ton 4x4 like mine with a gas motor. I cant figure out what is wrong with the tranny in my truck, and Im hoping this other allison will work.

Can anyone tell me if there are any differences between an 03 and 05 allison? Also if there is a difference between the allison in a gas engine truck and a diesel engine truck?

Thanks for your help!!
The flex plate appears to be different and if you replace the trans, reset the TCM to base calibration. Just scanned the factory manual and the only difference between gas and diesel was if you pull the trans and the 'flex plate vibration test'.
Torque converter may have different stall speed, no other differentiation noted. 5 speeds should be the same, 6 speed is different.
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