High Speed Vibration

[Powerflite]

I am getting a driveshaft type of vibration at 75mph and greater in my '70 Satellite. At lower speeds, everything feels great. It is there under acceleration as well as deceleration. I have double checked for bent rims and bad tires. All looks good. My U-joints are new.
It didn't vibrate before I:
replaced the original 8 1/4 with an 8 3/4 from a '69 B-body.
installed a 700-R4 trans with an extra length yoke and a conversion U-joint.

The output shaft of the trans is installed at the stock height and location so that isn't a part of the problem. From the picture, it looks like the yoke is too far out from the trans, but it is extra long so it is making the proper amount of contact inside the transmission. My question is if this extra-length yoke could be causing the high speed vibration. I don't want to go get the driveshaft lengthened with a new yoke if that isn't likely to fix the problem.

Thanks.

 

[RustyRatRod]

The first thing that jumps out at me from that pic is, that slip yoke sure is a long way out of the tail shaft housing. Other than that, check the usual stuff. Pinion angle, make sure the trans mount is good and on that conversion u joint, I'm not a fan. Never have been. I know they can be used successfully, but I just never have liked them. It's just a personal preference.

 

[dryheat]

Inquiring minds need to know 700-R4??

That's a lot of changes to the drive train to try and diagnose a vibration.

Lets start with the simple stuff ... given the u-joint conversion with the extended yoke have you verified that the drive shaft is balanced?

 

[Powerflite]

Inquiring minds need to know 700-R4??

That's a lot of changes to the drive train to try and diagnose a vibration.

Lets start with the simple stuff ... given the u-joint conversion with the extended yoke have you verified that the drive shaft is balanced?

Yeah, I just got off the phone with a driveshaft shop. He asked me the same thing and told me that I need to have the driveshaft re-balanced with the new yoke. I didn't know that they were balanced together and that it needed to be re-done after changing the slip-yoke. So I guess that is probably the source of the problem. I also checked the length of the yoke compared to a stock one. It is only about .75" longer than stock so I can't see how that would make much of a difference. So I'm off to get it re-balanced.

 

[RustyRatRod]

Why did you choose the 700, when the 200 would have been much better? Even all the chebbie guys make that mistake.

 

[300]

I have 2 Chevs and 2 Mopars. That makes me Chebmop or MopCheb

 

[Powerflite]

Why did you choose the 700, when the 200 would have been much better? Even all the chebbie guys make that mistake.

Much better in what way? The reason I chose it: It is an overdrive trans that fits with very minor mods to the floorpan and the T-bar crossmember. It fits. The 200 might fit if you don't mind lowering the output shaft a couple of inches from stock or hacking up the lower left portion of your T-bar crossmember. But this one sits right where it is supposed to be.

Internally the 200 is like the 904. Smaller, weaker, and more efficient. The 700 is like the 727, bigger, stronger, but less efficient. A 200 can be built to be stronger, just as the 904 can, but that is mostly irrelevant to me because I have no intentions of building a custom trans. The 700 is stronger right out of the box (the box in this case is an '89 crapmero), is well suited to my mostly stock 318 in a heavy wagon, and *it fits*.

You can read about my swap here:

http://www.forbbodiesonly.com/mopar...5647-700R4-Swap-into-66-70-small-block-B-body

as well as a short comparison to the case dimensions of a 200 vs. 700 on page 2.

 

[RustyRatRod]

Wrong. The 200 is both larger and stronger than the 700 where it needs to be. The gear ratios are also better. You've never had them side by side, or you wouldn't say that. It's as apparent a difference as the turbo 350 and 400. You need to remember, there are two different 200s. One is distinctly a light duty transmission, which I am not talking about. The other, is the same transmission that GM chose OVER the 700 to put in the Buick Grand National cars and Monte Carlo SS. That's the transmission I'm talking about. Trust me. I know what I'm talking about. You chose the inferior transmission. It'll work, but it's nowhere near as strong or as quick. My buddys 29 Model A ford rat rod has a 200 in it. He just swapped in a 392 Hemi with dual quads. He's also half owner of the transmission shop I used to work for. They don't take the internet's word for it. They take direct experience. You are right in that some of the internals in the 700 are bigger. But that doesn't mean better. All things equal, I garrantee you the car with the 200 will be in front everytime. Al the chebbie boys fall for them for the 3.06 first gear, but that's a mistake. I'm not sayin the 700 is crap. It'll work fine. The 200 is just a faster and better transmission. It's funny. All the transmission shops know it. GM knew it, too.

 

[Powerflite]

I have a built 200-4R in a '63 Nova so I am very familiar with them. But I should have said, it is irrelevant to me because the 700 fits better. It really does. I would love to see proof to the contrary. Every 200 conversion I have seen involved bad angles and/or cutting. When I measured it out, I couldn't make it work well with the 200 either.

That low gear *is* well suited for a wagon like mine or a truck too. Drag racing times have no benefit for me here. Also, I don't disagree with you about their potential strength because I have witnessed it myself, but I do wonder why GM went with the 700 in the corvette and stayed with it to the end as a 4L60E. If the 200 was so much better, why did they throw it to the wayside? Maybe it was seen as more of a BOP thing that the chiefs wanted to eliminate.

 

[RustyRatRod]

I think that's the answer. There are WAY more BOP dedicated housings than the dual pattern....and to my knowledge, there never was a chebbie only unit. Either transmission is a good unit. It all depends on personal preference. I'll tell you this....and I'm sure you'll agree. Considering what you have to do for a 518 swap, I bet you'd say the 200 would be far easier. lol I try to preach the GM transmissions when people start talkin overdrive, but usually it falls on deaf ears. How the hell does the car know what's in it? lol But getting back to your problem at hand, like I said, I would check all the stuff you normally would in an OE application FIRST. Treat it like it's not a swap. Then if you run out of options, look at the swap. No sense in making it more difficult than it is right off the bat. It's probably somethin simple.

 

[Meep-Meep]

Some things to check: Phasing of driveshaft weld yokes. They should be zero, or in phase with each other only if the driveshaft leaves the tail shaft with an offset in one direction. For example it shouldn't move up or down AND over to reach the pinion yoke. Also the main shaft can't be skewed. The ideal situation is the main shaft CL and pinion CL should be lined up as if they are connected by one common shaft but with a lateral offset to keep both U joint angles the same.

I became a believer in the 200 when I saw a 4000 lb GTO running 10.0's and carrying the front end several feet out of the gate on every pass.

 

[Supershafts]

You can't change the slip and then expect no vibrations.. You need to balance the shaft, you changed the balance when you removed the original slip which is part of the shaft and needs to be there when balanced.

When you change a joint and put the slip back the wrong way it'll be out of balance.

Yes it's that important.
.

 

[Powerflite]

Thanks for the great info. I had no idea it was that sensitive. With the original yoke, I had 2 large weights at the front of the shaft and 2 smaller weights at the rear. After balancing, they removed both weights from the front and added 1 on the opposite side on the rear, effectively cancelling some of the original weight there. So it seems the original yoke was not nearly as well balanced as the new one. That should make a big difference. I haven't had a chance to test it yet, but I will let you know how it goes as soon as I do.

 

[Meep-Meep]

I have had slip yokes on and off to change U joints and had no problems. Not saying the balance won't change, but I don't recall any major vibrations after the repair.

 

[Powerflite]

I got a chance to take the car out today and took it up to 90 mph before I saw a pair of motorcycle cops ahead of me. Vibration is completely gone! Feels so much better now.

I suspect that the reason I had so much trouble with mine is mainly because my old yoke was very unbalanced from the factory and the new one wasn't. If you start with a yoke that is well balanced to begin with, it may not matter as much if you turn it around during a u-joint change. But if you see any weights at the front of the driveshaft, you had better beware because any change is likely to have reverberating consequences. But it doesn't take much effort to put it back to the way it was so that is a good rule to follow.

 

[Supershafts]

I have had slip yokes on and off to change U joints and had no problems. Not saying the balance won't change, but I don't recall any major vibrations after the repair.

Many people don't even notice the little vibes, they're not all major type vibes that loosens your teeth, they don't have to be felt, they could just be a noise very much like what tricks people into thinking they have a exhaust drone or it could be a hum or buzz but those are all an imbalance of the shaft.
I haven't seen a shaft built with slip change to another slip, even of the same style and not need balancing.

Same with flange yokes.

Always put it back the same way, and even sometimes putting it together wrong and running it with the vibe and then changing it back, sometimes can still cause the shaft to need to be re-balanced and dropping shafts, as odd as that sounds it's true you can launch a car at 9000 rpm but dropping a shaft can cause them to need balancing, it's why my shop truck has holders we found that some drivers driving causing the shaft to knock around in the bed was enough to change the shaft to need balancing.

.