Vibration

shadow88 · Mar 21, 2014

After putting in my lift I have a driveshaft vibration, my lift came with rear springs, the springs had wedges already on them, this lift was for a ranger, could this be the reason I have the vibration? Because the driveshaft in my b2 is shorter? I didn't have this vibration before the lift, and the vibration is most noticeable when I'm down shifting or coasting

4x4junkie · Mar 21, 2014

shadow88 said:
Because the driveshaft in my b2 is shorter?

Could be...

Are you running a double-cardan type driveshaft?
Is your pinion u-joint angle ok?

shadow88 · Mar 21, 2014

I'm running the stock drive shaft, and I'm not sure what my pinion angle should be at

shadow88 · Apr 4, 2014

So I took out the wedges and the vibration almost went away, I called rough country about the wedges and they said they were 6 degree! That seams a little much

ab_slack · Apr 5, 2014

There you go, some hard evidence it is related to the wedges.

Is your drive shaft a CV type or a U-joint type? Most factory stock were CV but some did get the u-joint type . Since you have a 90 it seems more probable for the latter. I do not think the factory u-joint type were double-cardan however.

With a non-double-cardan u-joint shaft the transfer case output shaft axis and differential input shaft axis need to be relatively parallel to cancel out rotational speed differences.

Also with the short length as it is lifted angles increase and there is a point reached, even when axis are parallel, that angle is too steep for smooth functioning of the driveshaft.

I am guessing the wedges are supposed to help that angle by tilting up the input shaft of the differential a bit to help keep the drive shaft angles from getting too steep, but it threw off the alignment so that rotational velocities didn't get cancelled out. They probably also help prevent the shaft from running out of travel in the slip joint.

Without the wedges that is back in alignment, but you have the steeper angles. That could be the remaining vibration you are experiencing. You not running out of travel on it are you?

I believe a double-cardan shaft will be more tolerant of higher angles with a lift and, I think the axis of the transfer cases vs differential don't need to be parallel. As such the wedges are beneficial to keep the u-joint angle down and help with travel issue.

shadow88 · Apr 5, 2014

I have the u-joint style and I have plenty of travel left, until I decide to try some extreme flex, but I still think it could flex far enough as it as to come apart

shadow88 · Apr 5, 2014

Non double carden

ab_slack · Apr 5, 2014

All that makes sense then. Why the wedges caused vibration cause that messed up the angle setup. So really the only thing to worry about without the wedges is how bad the angles are. I don't know at what point that becomes a problem however.

4x4junkie · Apr 5, 2014

shadow88 said:
Non double carden

That wouldn't be a stock driveshaft (and is what's causing your problem).

The stock shaft on your '90 most likely was a dual CV type (has enclosed CV joints at both ends of the shaft). These shafts are very failure-prone (even without a suspension lift) and is probably what led a previous owner to replacing it with the shaft you have now.

My suggestion would be to swap over to a double-cardan u-joint shaft (has 3 u-joints, one at the axle, and two together at the t-case), then set your pinion angle so that it's 1-2° down from pointing directly at the T-case while the vehicle is at resting height. This small bit of down-angle allows for both vehicle loading as well as leaf spring windup while you're under power.

On mine I'm using a shortened front driveshaft from a '92 Explorer as the rear driveshaft. No vibrations at all at any speed that I can tell.

shadow88 · Apr 5, 2014

Thanks for the info, as far as this not being the stock shaft, I'm thinking it is, I might be wrong but I've seen other members on here that have had the same shaft in a 90 b2, everything else on this truck has been stock, even the shocks, my speedo reads 41000, I know that's more close to 141000, but I'm in Minnesota and my fame isn't full of scale rust and it's real clean, I'm guessing this truck didn't get used much before I owned it

ab_slack · Apr 5, 2014

Well I don't think rust had much to do with the stock CV shaft failures. They were just weak for even the amount of torque the 2.9L could put out. My 88 BII had an issue around 75Kwhere the dealer told me the main drive shaft was bad and ended up having it replaced.

As I said before I've heard there are some BII that did have u-joint shafts. I don't know if 4x4junkie was saying they would have been double cardan types if it was factory u-joint type or if just saying they were CV (the most common).

What he says tho about having a double cardan and adjusting accordingly makes sense, but you could always worry about that when/if the existing one fails unless the vibration is too high even with the improvement. In which case what he said is probably your best bet.

4x4junkie · Apr 6, 2014

'84-'85 BIIs had u-joint factory driveshafts (maybe some '86-'87 also, but not real sure on those). They were all double-cardan type shafts. These used tiny 1210-series u-joints however, which you don't really want if you're going to be wheeling it a lot (mine from the Explorer has 1310-series joints).

Dual-CV shaft failures were very common. Having seen other BIIs with shafts like yours doesn't surprise me (my own BII had a CV shaft that was making noise when I bought it).

I know some people have cut down Explorer or Ranger rear driveshafts to work in BIIs, however they are not ideal being they are only single-cardan shafts. Front shafts from '91-'97 trucks work a lot better, though you need to also bring in the donor's t-case output yoke to replace your output flange, and a flange adapter to mate the shaft up to your rear pinion flange to be able to use it.

Here's what mine looks like (yours will likely be a little longer since I don't think you have a dual t-case):

Scrambler82 · Apr 6, 2014

Could be just bad joints, rust build up without any noise.

Take out the shaft, check it out.

Rowdy Fitzgerald · Apr 7, 2014

I agree with Scrambler. Start with the simple stuff first. Check to see if the U-joins are going bad, then check the slip yoke. Maybe the drive shaft is slightly bent, maybe a weight came off and now it's out of balance?

Scrambler82 · Apr 7, 2014

I just re-read the thread.
When you did the lift did you check out the whole front end, drive shafts (3), ball joints, tie rod ends, what about the alignment, chamber off ?

Also, if anything is wrong with the rear strings it, it might be that they are a little under rated for the extra weight of the rear of the BII but rears shouldn't hurt anything other than sag...

Start with the rear shaft, then the front main shaft and the two secondary ones. After that check the ball joints and tie rod ends.
Are the hubs manual or auto, maybe one is stuck in lock position ?

Just thinking out loud here... ,

Vibration

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