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I have a 2003 4L80 that someone put into a small 1ton chassis motor home about 5 years ago. This was a replacement for the OE transmission. It does not have a en-brake attached.
I could see where it was leaking from the output shaft. They tried to seal it with silicone. I already know I have the wrong output shaft so please don't state that fact.
1) It has a bolt on yoke.
2) The output shaft is for a slip yoke and takes a yoke tube.
3) Extension housing is casting #8677464 and takes a early 2.020" bushing.
So when I bolt down the yoke it pulls it into the rear seal & rubs slightly.
I know this isn't correct. The output shaft/extension housing are not mated. To me the output shaft needs to be 1/4" longer. The problem is there are 11 different 2wd output shafts and 4 different lengths. If you take out the 91-96 shafts that wont work at all. There is still 6 of them w/ 4 different lengths. The one I have is circled and if I'm correct I need the one on the right. the others are shorter and would make it worse, but the long one is supposed to be for the units with a brake drum. it is also 7/8" longer at 9" overall.
I'm stumped...
I had this almost fully assembled and took this all the way back down to measure the output shaft.
Last edited by mrvedit; May 1, 2023 at 10:33 PM.
Reason: Spelling in title to permit easier search
List of 4L80E output shafts taken from WIT parts manual. Ignore the red box in the image below.
The output shaft in your first picture I'm pretty sure is 34678RA if it has no lube holes. So the one circled in your images seems like it would be either 34678QAA (slip on 97+) or 34678QB (bolt on 97+) as possible options. Based on the length of the extension housing used and the need for it to be a 97+ and bolt on and your thoughts on it needing to be longer, perhaps this is the one you need? Check out ebay item #112005981686. I'd ask for a photo from the seller of the shaft with the tape measurer on it showing how long it is, as sellers tend to misrepresent parts all the time on ebay.
Last edited by 5.7stroker; May 2, 2023 at 11:27 AM.
List of 4L80E output shafts taken from WIT parts manual. Ignore the red box in the image below.
The output shaft in your first picture I'm pretty sure is 34678RA if it has no lube holes. So the one circled in your images seems like it would be either 34678QAA (slip on 97+) or 34678QB (bolt on 97+) as possible options. Based on the length of the extension housing used and the need for it to be a 97+ and bolt on and your thoughts on it needing to be longer, perhaps this is the one you need? Check out ebay item #112005981686. I'd ask for a photo from the seller of the shaft with the tape measurer on it showing how long it is, as sellers tend to misrepresent parts all the time on ebay.
I ordered a 34678QBB THIS morning. Not sure what the difference is. The description is 8-1/8" overall bolt on yoke w/o-ring groove. My hope is the yoke bottoms out on the end of the splines before it hits the rear seal.
The fix was the 34678QBB shaft that I ordered.
FYI the yoke bottoms on the ledge of the o-ring groove leaving the proper gap at the extension housing..
Good to hear that the 34678QBB fixed it. I wonder what the difference is between 34678QB and 34678QBB.
They have the same description so I'm not sure. The shafts in the pictures show an HD version. The part numbers in the description are hard to run down. There isn't much information from GM because they have all been discontinued. So it could be just like the difference between a 4L60E output shaft and the 4L70E output. Just the hardening process.
My guess though is it is just the difference in one company's part # system against the other...
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4L80E Output shaft trouble 
