4L80E w/ Transmission Drum E-brake Leaking

[jcwren]

Man, this stuff gets confusing. And factory service manual is pretty vague on a lot of it, too. According to the identification chart you posted, it seems what I should need is the "heavy duty fixed yoke", not the "long heavy duty fixed yoke":

3. HD truck series with tail mounted brake. 5.5" sticks out.
4. 4 wheel drive option, much shorter in length. Only 3" sticks out.
5. Long, HD fixed and sticks out 6.5-7"

I did just measure mine as a sanity test, and it's right at 6.5" from the seal. But it is tapped at the end, and the post says this:

Also if the output shaft has a hole that was tapped for a 1/2" bolt, then it was designed to have a fixed yoke and a driveshaft that slips.

I can see far enough down the sleeve to see that it's fully splined. Sigh. This was supposed to be as easy as replacing a seal. Camera didn't want to focus where I wanted it, but it's good enough to tell.

I put a dial indicator on end of the output shaft, and I'm getting about 0.030" deflection in either direction, but that's with some definite pressure. Seeing how the output shaft is connected to the main shaft, and there's no intermediate bushings, this seems reasonable. I'd think that 0.009" number is when the extension housing is installed, and the bushing is supporting the output shaft. The FSM doesn't list any tolerances for this sort of thing (at least that I can find).

The two piece drive does have a slip joint, but it's between the carrier bearing and the differential. I would have expected some slip to allow for the motor/transmission flexing.

You must be registered for see images attach

You must be registered for see images attach

 

[stutaeng]

Here's my setup. My source was an article from Sonnax and it listed endplay as 0.007" to 0.019". I don't believe the tailhousing extension does anything for the measurement. There's thrust washer right on the inside of the case that establishes this. I figured you can check since you don't know anything about it, and you are there already.

I think you are measuring deflection perpendicular to the shaft axis? If you can get it on a smooth surface, that's called run-out, like if the shaft is bent. I don't recall any specification for that, or checking it from my recollection.

What service manual are you using? I don't know if the ATSG manual has anything on the different output shafts and yokes, I don't recall.

Sorry, I wish I was more help. :-(

You must be registered for see images attach

 

[jcwren]

You been a MASSIVE help, thanks very much! You're correct I was measuring run out, not end play. I'll have to measure the end play in the morning.

I have the 4 volume GMT400 factory service manuals. I'm thinking of ordering the ATSG manual, although I was hesitant as a number of reviews said the illustrations were really poor resolution and hard to read.

 

[stutaeng]

I ordered the ATSG manual, and DOES look outdated and yeah, illustrations are not too good.

You can preview it here: https://www.google.com/url?sa=t&sou...kQFnoECA0QAQ&usg=AOvVaw32eAoQwy6d5MGXvZ5X5hyE


Page 82 & 84 are the only ones that seem to mention the tailhousing. I didn't see specific mention of yokes though.

I've never done this, but I suppose you can clean everything really well and put some of that dye in the ATF, go for spin and check underneath with a black light. Leak source should be pretty obvious.

 

[jcwren]

Another one I saw recommended is this one, although I don't know how much it pertains to my needs at the moment.

xc_hide_links_from_guests_guests_error_hide_media

Maybe I'll just give Alex Taylor a call and see what she knows

 

[yevgenievich]

4l80e manuals and other info in the zip file:

xc_hide_links_from_guests_guests_error_hide_media

 

[jcwren]

4l80e manuals and other info in the zip file:

Thanks! Looks like lots of light reading material

 

[jcwren]

OK, here's what I learned today. The run-out seems to be 0.005" to 0.007", so we're good there.

Using a tape measure, I put the yoke on the output shaft, and set it where the seal would land on the seal face on it (about 7.25" from where the extension housing meets the transmission), the measured from the center support bearing to where the U-joint would land on the yoke (about 30.25", with the center bearing support bracket as far forward as it would go). This looks like the seal should engage well, and have the lip of the seal on the smoothest portion of the yoke.

The bolt I bought is useless (goodbye $21), as it's far too short, and it won't help on a slip yoke anyway. The shield shown in this picture doesn't do anything, but won't hurt anything, so no point in removing it. The spline shaft portion of the yoke doesn't go deep enough to engage the seal in the shield, and this wouldn't be present on a drum brake output shaft anyway.

I did clean up the seal face of the yoke today, and it polished up pretty well. So I'm hoping the leak was caused either by the seal face being too rough and/or the stub shaft center bearing support bracket being set too far back and the yoke seal face not actually in the seal. New seals should be here Monday, so hopefully I can assemble all this without the drum brake parts and confirm all my measurements.

I do need the bracket (circled in red) that the e-brake cable attaches to, as shown in the picture below. Unfortunately, I can't find a GM part number for it, so searches haven't turned up anything.

You must be registered for see images attach

 

[tpass]

I do need the bracket (circled in red) that the e-brake cable attaches to, as shown in the picture below. Unfortunately, I can't find a GM part number for it, so searches haven't turned up anything.

You must be registered for see images attach

that would be a fairly simple bracket to fab if need be, piece of steel with two holes and a 90 degree bend, probably doesn't need to be a very accurate copy.

ETA: I just looked at my bracket, its pretty beefy... but still looks like an easy project. Look for GM campers and P30 van part outs of the same era, they probably all have that same e-brake.

 

[jcwren]

that would be a fairly simple bracket to fab if need be, piece of steel with two holes and a 90 degree bend, probably doesn't need to be a very accurate copy.

ETA: I just looked at my bracket, its pretty beefy... but still looks like an easy project. Look for GM campers and P30 van part outs of the same era, they probably all have that same e-brake.

Any chance you could take a few pictures, maybe with a ruler placed for scale? I don't mind trying to fab one, but I can't find any pictures that show just the bracket (they're all pictures of the transmission, and just a little bit is visible here and there).