I went to install my new driveshaft's yoke into the tail of my TH400 and had a strange problem. It would go in part way and then "CLUNK". It wouldn't go in all the way. The splined shaft at the back of the transmission has a shallow countersink in it, but it is NOT TAPPED. At first I thought maybe I had a truck transmission, but I checked it again and it's NOT TAPPED. The truck transmissions use a special yoke that uses a bolt to hold it on, and the yoke winds up fixed instead of able to slide back and forth. I talked to Inland Empire Driveline (who made the driveshaft) and they had never heard of anything like what I had. They asked me to unbolt the tailshaft housing of the trans to figure out what was going on. This is what I found. The yoke can only slide on until it gets to the smooth larger OD part of the shaft right before that O-ring. So it's like a truck shaft, but it's not tapped. Maybe this trans was in something with a transfer case on it for 4WD or something and they swapped for a normal tailshaft housing? Or maybe it originally had some kind of "power take off unit" for a pump truck or something? It would have never worked with a normal bolt on yoke because it's not tapped. Kind of a mystery. Inland Empire made the driveshaft and they were really nice about it when I called them and they had UPS pick it up at their cost and they're working on the shaft now. I think they're going to machine out the splines from the last inch or so of the yoke and possibly shorten the nose of the yoke a little. They said they'd re-balance it and ship it back to me. They give pretty great service. If you ever have a driveshaft made for a TH-400, you might want to try sliding a long skinny ice pick sort of tool down the length of the splines on the tailshaft to see how far in they go. On mine the splines are only about 2-3/4" long and un-splined wider O-D part is about 3-3/4" inches down. I'm guessing the normal car tailshafts must be splined about 4-3/4" deep! Anyone ever had this problem before? What's your opinion on the o-ring? If I leave it there, it will seal against the ID of the yoke which will mean transmission fluid will never get into the splines and I'll have to rely on whatever grease I put on the splines to last forever as a slip joint. If I remove the o-ring, then transmission fluid will be free to lubricate the splines, I think? But leaving the o-ring might help to sort of support the nose of the yoke to keep it from rattling? I think maybe I should remove the o-ring though because I think it would be better to keep the splines lubricated. Any opinions on this? Inland Empire is a real nice shop to deal with. When I first ordered that driveshaft, it arrived on my doorstep in about two days! And they're being great about having to work on it some more now to get it to work for me. Thumbs up! Thanks!
The tailshaft you have is designed to be used with the "long" yoke that has a machined ID for it to ride on. You have to grease the splines, no trans fluid goes on them. And it has a vent hole in it. This design was used on full size cars in the late 60s-mid 70s, as far as I know. I notice that it's a long tail shaft transmission, they probably mostly deal with shortys at Inland?
I ran into a similar situation during mockup. The junkyard T-400 splines were dirty and wouldn't allow the yoke to slide all the way on. Pulling the tailshaft housing and scrubbing the splines with a small brass bristle brush cleaned it up so that the yoke seats all the way to the bottom. How long is your yoke? I have a HD Inland Empire and stock yoke, neither one of them is too long. I think the truck yoke is longer, but not completely sure.
I had the same problem on a truck I built. Spicer makes a yoke especially for this problem. I got mine from Denny's Driveshaft Service, but I bet a good local Spicer dealer could look up the part number, which I do not have anymore.
Thanks for the info! I think the wide angle lens on my camera makes the shaft look longer than it really is. I looked for a picture of my trans when it was together and found this. Looks like a typical "short tail shaft" I think. Aren't the long shaft transmissions obviously way longer? The end of the yoke definitely bottoms out on that unsplined larger OD part right before the o-ring. It needs to slide on almost an inch more to get fully on there so I can hook up the rear u-joints. And there's about 1" of polished steel of the yoke exposed out the end of the tailshaft when it bottoms out. So if they machine away an inch of the splines, it should slide in the rest of the way and solve the problem. And the new smooth bore that they're going to machine in the nose of the yoke should seal up against that o-ring. Thanks Squirrel for that info about the tailshaft area having no transmission fluid in it. I was thinking that whole area was going to be full of tranny fluid. So I should grease up the yoke really well and leave that O-ring on there I guess? I used red grease from a grease gun like the stuff I used for greasing up ball joints and tie rod ends. Is that the right grease to be using for the yoke? Or should I be using white lithium grease or something instead? Thanks a lot guys!
There are 3 lengths just like a 350 short4" medium8" and long12". Medium and long both require the countersunk(no splines for about an 1 1/2" or so) slip yoke. Very common,nuthin' special.
Okay. Thanks everybody. I learn something new every day. So the special Spicer yoke made for tailshafts like this must be about the same as the normal one, except bored smooth near the end to remove the splines in the first 1". And I guess that's what they're going to do to fix it. The yoke that came with my driveshaft was a Spicer, but obviously not the one with the splines bored out at the nose. Anybody have a favorite grease to use for the yoke splines? Or is any old grease fine? Thanks again.
Output is out of caddy.Use Caddy yoke or all little createtive work with welding disk grinder will remove o ring bump.
I just found out they already fixed it and shipped the driveshaft back to me and it's waiting for me on my doorstep. I'll give an update when I find out exactly what they did to it to modify the yoke and take some more pictures. I'm going to install it tomorrow morning probably. By the way, I measured the diameter of the un-splined larger diameter part in the area of the o-ring, and it's 1.372". So I'm guessing they probably bore out the end of the yoke to around 1.375" to make it so it slides right over that part instead of crashing into it. Thanks again
OK here's the yoke your looking for. Has a weep hole on the U-joint end and the missing spline to allow it to slide on the output shaft. Its a leaker on a "normal" 400 because of the weep hole.(ask me how I know). The missing splines are 1.765" deep and the inside dia. is 1.437" with a pretty smooth finish so as not to tear up the O-ring on your output.
Thanks. I wonder if the weep hole and the missing spline are there to keep it from building up pressure in the spline area as it warms up, or maybe just to relieve the pressure so it slides on easily initially without working like a bicycle pump? I wonder if it was transmission fluid leaking out of your weep hole, or just some excess grease that heated up and sprayed out. I'll post a picture of the reworked yoke. I'm guessing it'll look pretty much like that one. I'll check to see if it has the missing spline and if it has a weep hole. Thanks.
The hole is there to allow it to relieve pressure. If they machined the inside of the yoke just like that one, then you need the weep hole and grease the splines if you leave the o ring on the shaft. If not, dont' worry about it. notice the yoke shown has the plastic ring in the hole where the U joint cup goes...it takes that funky Saginaw U joint.
Not to hi-jack So will that yoke with the end splines removed work in the cube van 400 I have that took the bolt on yoke ? Will it hold up to a bbc, since it has half the amount of splines inside ?
Okay, I got the driveshaft back from Inland Empire Driveline and it looks like they shortened the end of the yoke by about an inch and they also bored away the splines about 1/2" deep. By shortening it, I think the end of the yoke won't even reach the o-ring anymore, so I don't have to worry about that. There is one spline missing, so that should help the spline area "breathe". It looks like it'll work just fine now. Thanks everybody for your help solving this mystery. Here's what the yoke looks like now:
This thread makes me shudder! I have installed many TH400 swaps over the years, some with parts of unknown origin, and I was so lucky that I didn't know this problem existed. If I have a choice of skill or luck, I'll take luck every time. Bob
late sixtys big block buicks have the same deal, and spicer is the place to look, very common and of no real concern, leave the oring and grease the spine.
I had a problem that I now find out is due the yoke not being far enough into the tranny. Ripped the rear seal and bushing out the trans 200 miles from home. Make sure the end of the yoke goes completely into the bushing. I would hate for anyone else to have the same problem.
So what i did on my daily to fix the problem was cut an inch off of my yoke with a grinder.... Is there any reason that shouldnt work??? I've been driving/abusing it for half of a year
Ok man, it's been 7 years. Shortening them yokes is not the thing to do and I'm picking myself off the floor that empire did that because they didn't know better and never saw anything like that.
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