Vibes AFTER SYE?

coach9119 · Apr 21, 2004

'90 XJ
3.5" RE lift w/full leafs
242 Tcase, AW4

I put in a Tom Woods SYE and drive shaft b/c I was getting knocking from slip yoke after the lift. Now after the SYE, I'm getting vibes...

The vibes start at MPH and go through 35 mph or so. After MPH, I get occasional harmonic vibes, but not too often. Also, I think I'm still getting a little knock when I let off the gas, but it's hard to tell.

Here's what I'm checking, please let me know where else to look.

1. before the SYE, Pinion angle was 7.5 at the diff and 7 at the Tcase IIRC. I'll measure again tonight to be sure all is well.
2. I had a little trouble with the rear bearing on the install, so I'll break down the shaft, SYE and bearing cover to be sure everything is seated right and bolts are tight.
3. Drop the front drive shaft to see if that's where the vibes are from.

questions:
Anything else I should be looking at?
Can the bolts on the SYE (SYE to output shaft, DS to SYE) be over torqued? I torqued them to 25 ft/lbs or so. too much? too little?
Did running without the SYE mess up the t-case? (probably 1k miles)

Thanks in advance,
Andy

Dirk Funk · Apr 21, 2004

spring wrap???

89xj · Apr 21, 2004

coach9119 said:
'90 XJ
3.5" RE lift w/full leafs
242 Tcase, AW4

I put in a Tom Woods SYE and drive shaft b/c I was getting knocking from slip yoke after the lift. Now after the SYE, I'm getting vibes...

The vibes start at MPH and go through 35 mph or so. After MPH, I get occasional harmonic vibes, but not too often. Also, I think I'm still getting a little knock when I let off the gas, but it's hard to tell.

Here's what I'm checking, please let me know where else to look.

1. before the SYE, Pinion angle was 7.5 at the diff and 7 at the Tcase IIRC. I'll measure again tonight to be sure all is well.
2. I had a little trouble with the rear bearing on the install, so I'll break down the shaft, SYE and bearing cover to be sure everything is seated right and bolts are tight.
3. Drop the front drive shaft to see if that's where the vibes are from.

questions:
Anything else I should be looking at?
Can the bolts on the SYE (SYE to output shaft, DS to SYE) be over torqued? I torqued them to 25 ft/lbs or so. too much? too little?
Did running without the SYE mess up the t-case? (probably 1k miles)

Thanks in advance,
Andy

what is your pinion angle after the sye install. it should not be the same as before the sye. your pinion should be inline( 3 degrees) with the drive shaft. tom woods web site has a pic of how it should be after the sye install. tom woods "geometry 101"

you may need to install shims

xjhm · Apr 21, 2004

i agree with 89... the pinion should point up, in line with the driveshaft (actually 1-3 degrees down from being in-line)...but after i shimmed mine i found it better at three degrees..
but still had harmonic vibes, i couldn't really feel them but could hear them... turns out my front shaft was emmiting them...
i found this out after i bought adj. uca's to help correct my caster ...

btw i have fixed lowers, but they are for my 3" rusty's lift with a two inch spacer

Danno · Apr 21, 2004

one last thing to try is to check the balance of the DS. I know this sounds crazy but I had a new Tom Wood's DS put on after the SYE was installed and it still vibrated like crazy. We did EVERYTHING we could think of to cure it. The last thing to do was to send it back and have Tom rebalance it and that cured it. That was quite astounding as TW's stuff is almost always very well balanced. shit happens as they say! If you get really desparate try that.

coach9119 · Apr 22, 2004

Knew I was forgetting something. The angle at the diff is 10 deg now - I had a t-case lower in at the last measurement. According to TW, I need little or no angle to the shaft, so this is almost certainly the problem.

I need shims, I guess, so I'll do some searches on the topic and post back if I have any questions.

Thanks all!

Andy

coach9119 · May 10, 2004

Just and update - it was the angles. I put in 5 deg shims and the vibes are GONE. :clap: :clap:

now if only that annoying knocking would go away.....

bchulett · May 11, 2004

coach9119 said:
Just and update - it was the angles. I put in 5 deg shims and the vibes are GONE. :clap: :clap:

now if only that annoying knocking would go away.....

Question:

Do you have a CV shaft ?

I'm curious because I have the same setup and with same problem. I'm running a RE 4.5 but don't have a CV shaft. I think I've read somewhere that you're only supposed to angle the pinion in-line if you're using a CV shaft --- please correct me if I'm wrong.

Thanks.

coach9119 · May 11, 2004

I do have a CV shaft, and you are correct. With a CV shaft, the pinion should be in line with the driveshaft (angle should be 0). With a non CV shaft, the operating angle needs to be the same (or very close) at the t-case and the pinion. I found several good references on this, first on the Tom Woods site, and second on Pirate 4x4.

The tom woods stuff is here: http://www.4xshaft.com/ under "Tech Info"
The p4x4 articles are here:
http://www.pirate4x4.com/tech/billavista/PR-shaft/index.html

Hope that helps,

Andy

Vibes AFTER SYE?

coach9119

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