Excessive yoke outside trans?

[bob8619]

1968 C10 long bed, one piece drive shaft, TH350 transmission. I have about 1.25" exposed yoke but there is just under 3 inches of spline engagement.

Couple people in the truck forum suggested that the exposed section of yoke may be to blame for the bouncy hopping type feeling I get in the truck in the 50-55mph range. I'm certain that the spline engagement is sufficient but is there any harm in the 1.25'' exposed? Someone said it becomes unbalanced when there is too much exposed yoke shaft.

[PGSigns]

What you have is not to far out. I like to see an inch so you are really close. For bouncy hoppy I would look at wheel bearings, tires, shocks, if the truck is lowered the pinion angle, drive shaft balance, and go from there.
Jimmy

[cadillac_al]

I think the yoke looks ok too. How's the trans mount? Didn't those trucks come with a 2 piece drive shaft? could be pinion angle issues.

[bob8619]

Just swapped the mount out yesterday so it's good now. I think thast they came with 1 piece and also 2 piece but I'm not positive about that. The engine is a 305 transplanted from a camaro so who knows what else isnt original.

[nonstop]

Has it always had the bounce? The yoke is sticking out a little far, but I wouldn’t be concerned with its length. Your driveshaft looks like it has seen better days. It looks like it has been added on to. The end doesn’t even look welded on (at least looks like that on my phone). The shaft should be balanced with the slip yoke (your yoke looks newer than the shaft and likely not balanced with it).

[homemade87]

I like to see about 3/4" . This moves the u joint closer to the trans . The u joint center line closer to the trans will lessen the ( let just say the up and down moment at the joint ) . The more the splines are engaged helps also .

If to far out this will usually create a vibration , not a bounce . So I think your problem is else where .

[bob8619]

I've only had the truck for a couple months now but it has done it for as long as I've had it.

My mechanic said it's due to excessive run out on two tires so I took it back to where I bought the tires and they disagreed that the tires have any run out. To experiment I took the back wheels off and put jack stands under the axle and put it in drive and there was a ton of vibration (not the hopping , but vibration) I removed the shaft and found that the cap in the yoke had side to side play so I got a new yoke. Didn't try it on jack stands again but the hopping remains.

I remembered that the previous owner had pieces of 2x4s in the rear springs, so to experiment more I put the wood back in them. I no longer get the hopping feeling when the woods in there. Not sure if that is because I'm stiffening up the rear end so much that its masking the issues or what.

[YoungPup1977]

305 swap gone wrong.....start with the driveshaft, looks to be a combed job driveshaft being welded to fit the vehicle...which will create your vibration....start there than go to the "wood in the springs"

[68gmsee]

I ran my 69 with a 350/350 with at least that much yoke shaft showing and thought it would be a problem but never had any. I towed a tractor and trailer and hauled lumber etc. with it but never dogged it.

If it worries you of course you can get another drive shaft made but there was a time that I thought about drilling new holes and moving the motor mounts back between the front and back mounting holes. I still would have had room between the distributor and firewall.

[bob8619]

Originally Posted by 68gmsee

I ran my 69 with a 350/350 with at least that much yoke shaft showing and thought it would be a problem but never had any. I towed a tractor and trailer and hauled lumber etc. with it but never dogged it.

If it worries you of course you can get another drive shaft made but there was a time that I thought about drilling new holes and moving the motor mounts back between the front and back mounting holes. I still would have had room between the distributor and firewall.

It doesn't bother me, unless it's the cause of my hopping issue. I was just trying to determine if it's true that it can cause an imbalance as someone else had suggested.

[B. W.]

As others have said, just based on the pic, I don't like the double welded drive shaft. Not the proper way to shorten or lengthen a shaft. I'd fix that first, go from there. (Even if it's not your issue you want that fixed)

[bob8619]

Originally Posted by B. W.

As others have said, just based on the pic, I don't like the double welded drive shaft. Not the proper way to shorten or lengthen a shaft. I'd fix that first, go from there. (Even if it's not your issue you want that fixed)

Yeah I'll bring the shaft in tomorrow. Is the flaw you guys see repairable or will I just be needing a new staft?

[68gmsee]

Yeah, if the shaft was either lengthened or shortened at that extra weld point it may be a weak spot. I had one shortened once on a beach buggy but I cut and welded it right where the yoke was welded to the drive shaft and had it rebalanced.

Another thing that can cause bouncing or hopping may is bad tires or shocks. You can swap tires around to see if you can determine where it's coming from. If it seems it's under the truck it could be rear tires or shocks or driveshaft. Front tires or shocks you can sometimes feel on the steering wheel.

If it is shocks, sometimes the only way you can tell is by bouncing the corners but that may be hard to do since springs and coils are usually heavier than cars. I usually just remove the shocks and check them that way. If it's motor mounts you can check by jacking the engine up slightly.

[68gmsee]

Originally Posted by bob8619

...Is the flaw you guys see repairable or will I just be needing a new staft?

A good driveline shop will be better able to tell you but since you are taking it in and it doesn't cost a arm and a leg have them retube it.

[bob8619]

I only have one rear shock and I was down there looking around and noticed the upper shock bracket was loose so figured I'd knock the rivets out and use some bolts to hold it tight. So far, the hopping is gone. If it was that simple I'll be happy. Even if that was it, I will still get my drive shaft dealt with.

[YoungPup1977]

Wood in the springs is a dead give away for bouncy shocks. Sounds like a few issues to work thru before driving cross country. Have fun
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