Thread: Minimum distance transmission yoke to frame

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Hi,

I am installing a 700r4 tranny on my 1962 Vette. I end up having the transmission yoke at only about 1/4 inch above the frame. I have a polyurethane transmission mount. Is 1/4 inch enough or will it hit the frame when driving? The tranny is connected to a 440 hp 383 stroker.

Is it too close?


Thanks,

Chris

Although in theory the transmission doesn't move in relationship to the frame, I would be pretty nervous about running things that close. If over time the polyurethane mount compresses slightly, or on a hard launch the engine/transmission torques a bit in one direction, you could grenade the transmission case. ----By the way---the yolk looks like it is too far out of the transmission housing. Optimum distance with suspension loaded (under full weight of car) is about 1" from the end of the tranny case to the back of the yolk.

Originally posted by brianrupnow
Although in theory the transmission doesn't move in relationship to the frame, I would be pretty nervous about running things that close. If over time the polyurethane mount compresses slightly, or on a hard launch the engine/transmission torques a bit in one direction, you could grenade the transmission case. ----By the way---the yolk looks like it is too far out of the transmission housing. Optimum distance with suspension loaded (under full weight of car) is about 1" from the end of the tranny case to the back of the yolk.

Ok, I will try to move the transmission up a little bit.

This is a restored chassis sitting on jack stands. On the picture there is no load on the suspension and the drive shaft is quite angled and I guess the yoke will slip in a little bit on full load. On the picture the distance between the yoke and the transmission case is about 1 1/2 inch. I'm not sure how much loading of the suspension will affect that distance.

You can see the angle on this picture.

I'd shim your back mount up 1/2" or so.

Originally posted by R Pope
I'd shim your back mount up 1/2" or so.

The transmission is dropped by installing two steel blocks on each side of the transmission mount. I'll shave off 1/4" to 1/2" from those blocks which will put the yoke 1/2" or more above the frame. That should do it I hope.

Any more comments on how far out the yoke is? I had the drive shaft custom made and the shop decided that this was the proper length. I thought it looked a bit too short, and now I'm not sure if I should take it back to the shop or not. When I put a load on the suspension, the yoke is still about 1 3/8" from the housing. Is that too much?

I would wanna know how much of the yoke was on the shaft. You need a little clearance for when the rear end goes up and down and the yoke slides in and out of the trany. This way when you hit a bump it does'nt bottom out the yoke in the back of the trany. If the drive line is level or parallel to the trany you won't hardly need any play but if it's angled like your photo, the more clearance you'll need. The car does need to be sitting down on the ground to see what angle the shaft will be at. This way when the car hits a dip in the road and the rear end comes up and brings the driveshaft in line or level with the transmission the yoke will not bottm out in the back of the tanny. You should have at least a 1/2 inch of clearance from the yoke bottoming out in the transmission when the driveline is parallel or level with the tranny.


~ Vegas ~

I have about 1 3/8" of clearance toward the transmission when the drive shaft is straight.

The yoke is slid on about 2 1/2" (of 4" total) onto the outgoing axle from the transmission. Is this enough or will I run into problems here?

I think it is a little to far out, The problem that I have is that alot of the yokes the splines don't always come to the very end or the shaft that the yoke slides on to is recessed back in the trany or tail shaft. This will allow a little wobble which will tear up your rear seal in the tail shaft of the trany. Then you'll have the trany dripping trany fluid all the time, and if your anything like me that will drive you out of your mind. I swear I can hear that thing dripping, laying in bed at night. And it does'nt matter how many times you replace the seal after a couple of weeks they go right back to dripping again. Can you tell I've been through this before, several times but I hate to admit it. I would want it at least 3/4 of the way on the shaft. I would say 1 in. or less would be acceptable.


~ Vegas ~

Ok, I guess you're right.

I'll have a chat with the guys that made the shaft and ask them to make it longer. I don't want to ruin my transmission.

Thanks guys for all the input!

Chris