Spring Perch Shims?

[shawn]

well i put the spring-over that was in my '86 long box into the '91 shortbox and there seems to be a new drive-line vibration. its not bad, but i definitely feel something is there and it shows abit in the rear view mirror. both truck are 5 speeds and there is no t-case drop.  a friend suggested shims and low and behold another friend has a new set to spare. my question is does anyone have experience of this kind of thing and do you, dear c.c. member, think it will solve my vibe. all input greatly appreciated.

[HOrnbrod]

Axle shims are used to correct excess pinion operating angle caused after a lift. Go to the Tom Woods site, get and angle finder at Lowes or elsewhere, and measure the angle. No way anyone can recommend what degree shims you need until we know that.

 

http://4xshaft.com/techinfo.asp

[Biotex]

If you do go with shims, use only steel ones and IMO it is best to tack weld them in a couple of places. They have been know to get loose, crack and fall out. It is well documented.

[shawn]

uuuuugh.  i picked the wrong day to fail geometry  :(     with a straight shaft ( no double cardan), i don't see how any of the angles would have changed. only difference is the t-case sits  about 5.5 " higher than it was. i've read alot but at this point I'm not even sure if the housing should be rotated backward or forward ....... 

  ive also seen posts that suggest 1 degree per inch of lift.  from what i gather, in this set-up the pinions should be parallel regardless of the hieght difference.

[shawn]

i should have added in my original post that i do have the chevy drop shackles on. they are the 2 hole kind and are set on the lower-amount -of -lift setting, so in that configuration they are about 1" longer than stock.

[Biotex]

The 1/2" lift shackles will raise the pinion up.  Could be your vibration.

[shawn]

 in the end a 1.5"  t-case drop solved pretty-much all of it.  the slip yoke wasn't in far enough. the drop brought it in quite abit but could probably use an inch longer driveshaft too.  (or thereabouts).

[Eagle]

Use a YJ slip yoke. It's longer, and it also allows a better range of operating angle.

 

And it's much cheaper than a new driveshaft.

[HOrnbrod]

The YJ slip yoke is 5/8" longer, that's all. But maybe that's enough for you. There are much longer yokes available if not.

[shawn]

Eagle, that's an awesome tip!  that might be just the little bit extra that I'm missing now.

 and Hornbrod, i may be coming to you for ideas if i need a bit more. thanks guys.

[HOrnbrod]

YJ Slip Yoke

 

 

GM Long Slip Yoke (Ebay)

 

[a4xnut]

21 September 2013 - 09:30 PM

The YJ slip yoke is 5/8" longer, that's all. But maybe that's enough for you. There are much longer yokes available if not.

 

 

YJ Slip Yoke

 

 

From where I sit, the one labelled "MJ" appears to be longer than the "YJ" one.

[Incommando]

YJ Slip Yoke

 

 

GM Long Slip Yoke (Ebay)

 

What would be a good vehicle source for that GM slip yoke?

[HOrnbrod]

HERE is one source. The ones using the 1310 u-joints that is.

[92tanMJ]

 in the end a 1.5"  t-case drop solved pretty-much all of it.  the slip yoke wasn't in far enough. the drop brought it in quite abit but could probably use an inch longer driveshaft too.  (or thereabouts).

That's an awfully large tcase drop imo...More than one inch is pretty hard on the motor mounts and I have heard, never seen, but heard of people with 2" drops with their mechanical fans hitting the radiator.

 

 

Noob question.. How is a longer slip yoke going to help with vibration? Aren't the vibrations caused by the angles of the joints?