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Intolerable slip yoke issue. (np208)

4x4blaze

4x4blaze

That's not going to work
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Hey guys, just recently finished a lift on my K5... Or so I thought...:angry1: Lifted it 3" with 4" of total lift in the rear(2.5 ORD shackle flip, super shackles, zero rates). Also had my stock driveshaft lengthened within 1 - 1.5" of slip yoke showing. Had also shimmed my rear end and got really good angles which are really close to each other. EVERYTHING SHOULD BE RIGHT.:mad:

BUT, for whatever reason when coasting, I get a grinding noise. Under load, everything is fine. Had it up to 75 and it was smooth as a bird. until you put it in neutral and/or let off the gas and there is no load on the shaft. Then it makes the grinding noise.

What gives? This is not a huge lift. Just big enough to clear 33's. And I know that a cv shaft or slip yoke eliminator is more than likely the golden ticket, but I've dropped thousands into this thing recently and quite honestly can't afford to keep this trend going. I just want to drive and enjoy my truck. Any help or input is appreciated!

Thanks guys!
 
If it makes you feel better that's probably the last thing to do.

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Theres really no other solution to eliminate this issue? Just find it hard to believe. So many of these trucks are lifted. And theres no way they all have this vibration issue.... What did i get myself into.......
 
It's a rabbit hole. Joint angles need to be equal and opposite but they still have maximum operating angles. You are well outside those maximums. Some get lucky. Some dont.

I drove mine on a 6 inch just like that for a couple years. I had no other option. You at least don't daily this.
 
Wow! and yeah, shes honestly just my weekend sidekick!& As much as I hate to say it, what about dropping or clocking the transfer case? this vibration isn't horrendous, just annoying. And when I swap in my 6 lug 14bsf, then I will more than likely have a double cardan shaft made.
 
And, Unfortunately its going to be a 2wd truck this summer since I'm swapping 4.56's in the rear(which will eventually end up in my front axle) when I swap in my 14 bolt.. So im not exactly worried about the front shaft angle.
 
You say it smooths out under load.
Only vibrates on coast or decel.

So under load, the torque wraps the pinion upward.
On decel, downward.
Could your pinion angle at rest be pointed down too much?
Maybe shim it up 2 degrees.

You could also lower the transfer case.
An inch.
Use square steel tubing.
It will change the output shaft angle so you'll have to adress pinion angle again.
But lowering the tcase will reduce the operating angle of the front u-joint a little bit and rear ujoint op angle a tiny bit too(on rear driveshaft only).
Actually makes things a little worse on front shaft.

If I were in you position, i would temporarily relocate the bolt stretch spacers from above the frame rail to between cross member and frame.
Not a permanent solution but quick and dirty way to see what happens with the vibes having the t case lowered an inch.
At least give you an idea.
Don't leave it that way.
Get some steel and make a t-case spacer if you decide to make it permanent.
 
When you swap to 4.56 gears your driveshaft will be going faster at the same speed. It may make it worse. May not.

Dropping the tcase may work may not. Worth a shot.
 
obijuank5 said:
When you swap to 4.56 gears your driveshaft will be going faster at the same speed. It may make it worse. May not.

Dropping the tcase may work may not. Worth a shot.
Click to expand...
Oh yea, i just remembered.
Mine is a diesel.. no distributor..
Just a silly vacuum pump that can be clocked away from firewall.
Be careful your dizzy dont get squished.
 
FYI you can't get a SYE for a np208. If you end up thinking its the 208 or need a CV driveshaft.. then find a np241. personally I'd be looking a np241 already cause the 208 slip yoke is garbage and I'd do a 241 before I screwed around with dropping the transfer case lower.
 
Blazooki said:
FYI you can't get a SYE for a np208. If you end up thinking its the 208 or need a CV driveshaft.. then find a np241. personally I'd be looking a np241 already cause the 208 slip yoke is garbage and I'd do a 241 before I screwed around with dropping the transfer case lower.
Click to expand...
Tom Woods makes a SYE for the 208.
32 spline though.

Here; http://www.4xshaft.com/SYE_detail.asp

But the np241 does have a lower low range than the 208.
Sounds like the op is planning major changes down the line anyhow.
 
I had a '69 Cougar that drove smooth as silk up to 80 mph,but when you coasted or let off the gas,it growled,grinded and vibrated like crazy--thought it was the u-joints,but replacing them did nothing to help..then I discovered the yoke on the rear diff was loose,the pinion nut had backed itself off I guess..torquing it back up to spec eliminated the vibration completely..

Might be worth a look, in case its your diff making the vibration..though its probably more driveshaft angle related on your truck..
 
I will say that I had wished for more of a selection in axle shims when I put the 14SF under my '90. Mine only has a zero-rate under the back, but that combined with the larger axle tube gave it enough lift to mess with the angles. I tried as best that I could to make the spring perches match original with my angle gauge, but I could have compensated there, if I had known. I had to play with it to quiet things. I run 33's with a little trimming up front, stock springs.
Yes, I know that I am not really helping...
 
Pretty much the only known sure fire cure for vibration after lift AND u-joint longevity is a double cardan at the t case and near zero op angle ujoint at the pinion.
I didn't go that route either though.
Already swapped out the gm 10 bolts for a 12b and d44 with lockers but only because I had already completely built them.
My plan is to wheel it as is for a few years while I amass a 14 bolt and D60.
No sense in wasting all that money I put into those axles.

So I compromised.
Saving the slip yoke conversion NP208 or who knows.. NP241.. or 205/203 since I already own a NP203.
A few vibes are not going to be the end of the world.
Just a reminder of better things to come.. and to replace the ujoints more often.
 
Verify that it isn't physically touching anywhere (like strap bolts to shaft yoke, or something like that) and the pinion nut is tight. You might need to come up another degree or 2, but this is a compromise between smooth under acceleration and smooth under coast. What is the total angle in the U-joint? They are sort of rated for just a few degrees, anything over 8 probably won't be smooth under all conditions, but a lifted K5 is likely to be 12+. You also want to make sure the bushing in the T-case is good and your rear yoke is holding the U-joint properly. The "ear" style yokes tend to wear over time and let the U-joint sit a little off center. Also, if the straps aren't tight that's a very good source of grinding-type noises.

If thinking of a SYE, they do help get some angle out of the joints by making the shaft longer. Have you considered an anti-wrap bar? I haven't heard feedback regarding U-joint angle issues, but they do hold the pinion angle steady over the different operating conditions and should improve this situation.
 
Really quick question before I drive home, would a double cardan driveshaft be able to be equipped with a slip yoke and still offer the same benefits as a slip yoke eliminator style setup?

Will reply in detail tonight when I have time

Thanks!
 
You can have slip yoke on the T-case (stock) with a C/V joint in the shaft. Several here have done it. There are still other advantages to the SYE, but if the only issue is vibe, just C/V might work. It does hang a lot of extra weight off the back of the T-case.
 
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  1. The slip yoke output on the T-case is at a different angle than the driveshaft, so it has a tendency to bind. Not a problem with stock angles, but with a lift, it can noticeably clunk when you let off the brake.
  2. SYE makes the driveshaft longer, so angles get better
  3. The fixed rear output is sturdier, centering the yoke with a roller bearing, vs. a bushing for the slip yoke. Better centering means less vibe and less stress on parts.
  4. No fluid loss when you pull the rear driveshaft. Easy to drive with no rear shaft.
I didn't mention the lack of long-travel options for the slip yoke because in practice it doesn't matter. Unlike the huge slip travel required for front leaf springs, you don't need much in the back.
 
Quick update: Installed the 1" tcase drop kit I recently purchased. And now my driveshaft has a total travel of 1/2" till it is stubbed against the tcase housing..... Afraid to drive it like this.. Only takes one time to crack the transfercase housing....
 
4x4blaze said:
Quick update: Installed the 1" tcase drop kit I recently purchased. And now my driveshaft has a total travel of 1/2" till it is stubbed against the tcase housing..... Afraid to drive it like this.. Only takes one time to crack the transfercase housing....
Click to expand...
You had the stock shaft lengthened before you got everything set up.
Dang.
I saved my stock driveshafts as "trail spares" and had new shafts made AFTER shimming and t-case lowering.
You could grab a stock shaft from a wrecking yard.
I think if i were you, i'd carefully take it for a spin on a flat section of road and see if the t-case drop even helped.
If it didn't, remove the drop and just live with the vibes until you do your 14bolt swap next year.
 
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