Bolt-on yoke TH400 to 4L80E
 

When I removed the bolt-on yoke from my TH400, it was pretty wet outside with trans fluid and was clearly seeping and slinging trans fluid all over the place. The bolt wasn't very tight at all. This yoke had an open end with a very thick washer. This washer was about 1/4" thick -- one side was smooth, flip it over, and the other had a slightly raised ridge machined into it.

I installed this yoke on my 4L80E, it was a tight fit over the output shaft and needed a tool rigged up out of a piece of all-thread and nut to get it to press on. Once it was fully seated, I made sure the machined side with the edge of the washer was facing inward, and tightened the bolt quite tight (I believe I looked up the torque for the TH400 in my FSM -- but that was months ago when I did it). Was there anything else I should have done to prevent seepage from this bolt area? I don't want it to start leaking on me later.

Before anyone asks, it's a multi-piece drive shaft with the slip yoke at the last segment, thus the bolt-on yoke at the trans.

Re: Bolt-on yoke TH400 to 4L80E
 

Any suggestions? I'll be working on this over the weekend.

Re: Bolt-on yoke TH400 to 4L80E
 

The output shaft should have a O-ring on it that the yoke slides over, They are left off alot of time during a rebuild, Heres a pic to show what im talking about.

Re: Bolt-on yoke TH400 to 4L80E
 

Ah, OK, so if it leaks, it is missing this o-ring. Well the 4L80E trans was freshly rebuilt, so I hope the shop put the o-ring on. I imagine either the TH400 didn't have one or it was worn out -- which is why it leaked. Thanks.

Re: Bolt-on yoke TH400 to 4L80E
 

If I'm not mistakin,,, isn't the nut of the bolt on yoke a one piece , crimped type self locking nut with the washer part of the nut?

I don't know the insides of the 4L80 but just a thought here,,, I don't think it should have required a makeshift press to pull the yoke in the output shaft should it???? I think I'd be looking for damage to the splines of the output shaft or the yoke.

Re: Bolt-on yoke TH400 to 4L80E
 

No idea if that's the way it should be stock. My 4L80E is exactly like the TH400. There is a threaded hole in the output shaft of the trans. The threads were the same as the TH400. What your saying is that there should be a stud in there? Really?

I had to use a puller to get the yoke off the TH400, which I understand is pretty common. It wasn't tremendous force, just more than I could exert on the transmission laying loose on the floor pulling with my hands. And I had to press it on to the 4L80E with a threaded rod and a nut. Again, it didn't need tremendous force, and after it made it past the first set of internal seals, it slid on much easier. Once it was on far enough, I simply put the stock bolt back in, and seated it the rest of the way, It's not a slip yoke, so I expected it to be a little tight. What I didn't know about was that the o-ring -- and how it would certainly lead to a leak if it was cracked or missing. If I get a chance, I'll yank apart the tail of the TH400 and see if the o-ring is gone. As for the 4L80E, well, I have no idea and I'm not in a position to yank that tail apart now at this point. I might, however, remove the bolt and smear some silicone under the washer just in case.

Re: Bolt-on yoke TH400 to 4L80E
 

LOL, no sir,, I worded that about as poorly as I possibly could have (damn vicodine)
I think I still have the bolt I pulled out of a 1ton van yoke / TH400.

What I was 'trying to say',,, the bolt 'looked' like a.....ohhh....... a body bolt! with the washer integral and part of the bolt head. But the hex was a bit thin, and the corners were rounded off on the top (like a grade 8 stove bolt )

I think it was thin to make sure the bolt didn't contact the U-joint at high angles or something. .. man that still sounds like a bunch of incoherent babble don't it.. ONE picture,, LOL It would explain everything. I'll look around the shop later today and see if I can find the thing. I know it's out there somewhere.

I guess all in all if the u-joint doesn't contact the bolt / washer you have,, "it's all good!"

I misinterpreted force needed in the 'used a puller'. I have a old cheep body slide hammer I stick through the u-bolt hole and gently tap the yoke off if it's tight,,, and a rubber hammer to put it back on. Using a puller would be much smarter and gentler on the bushings,, your just to nice to your trans LOL.

Re: Bolt-on yoke TH400 to 4L80E
 

Yeah, They need a good beating every now & then:lol:

Re: Bolt-on yoke TH400 to 4L80E
 

If you are worried about a missing O seal, you can pull the bolt/washer , clean the end (splines & yolk) with brake clean. After it dries good, break out the tube of "spooge"! Ill bet that a good app of high temp RTV will seal it;) crazyL

Re: Bolt-on yoke TH400 to 4L80E
 

LOL, OK, now I get it. All you had to say was a body bolt (or a flanged bolt).

Nope, mine is a Spicer yoke with a separate washer and bolt, but the washer appears to be machined for this purpose because of the lip on it, the thickness of it, and recess in the yoke. I forgot to mention this is a 1-ton chassis, not sure if that makes a difference. The original bolt had a slim, rounded head on it. So again, that looks like the right bolt. It came off of the TH400 and had no clearance problems. I would much rather have the aforementioned flanged bolt though. That seems better.

As for hammering the yoke, I put quite a bit of $$$$ into this drivetrain and usually make beatings with a hammer the last resort after trying other methods of force. I'm a fan of "work smarter, not harder."