SAS Dual-Case Front Driveshaft Problem (?)
 

I've searched and most people have this problem on the rear shaft, not front. I'm still thinking driveline...

I am just wrapping up the build on my '89 4Runner. Front SAS w/4" springs, dual cases w/Marlin gears in the rear case. I live in Colorado and drive a lot in the snow, so I need higher speed 4WD. Here's the problem I'm having: When in 4wd-hi I get a grinding noise coming from the t-case area when I accelerate or decelerate. Under load I get a little vibration but no death noises. I don't hear this in 2wd with the CV shaft on the rear.

I have a long spline Davez Offroad shaft with standard u-joints for the front. Do I need a front CV (thought that wasn't needed with dual cases)? What kind of things should I look for to solve the problem? The pinion flange and t-case output flange are both tight, though not parallel. Just looking for ideas!

Thanks.

If the flanges aren't parellel, the more the angle, the faster the DL turns the more the vibes will be noticable. I'm running a similar set up but with the CV front shaft, haven't been on many smooth surfaces in 4wd with much speed so not to sure if mine is will make noises. My front shaft is unbalanced too.

Can you post a pic of the front shaft angle? Is the shaft still phased correct?

I've always put a cv front and rear on a lifted Toyota if driving on road.

:wabbit2:

Picture; hopefully the angles at the pinion and t-case output are clear enough. Angle at t-case is definitely steeper than the pinion. I tried to keep the camera as level as possible. The driveshaft is definitely in phase. Also, I'm hoping now that I have a bumper and winch on it, the shackle angle will improve after some wheeling.

A few more for reference. Thanks for the help.

you have too steep an angle you're gunna get vibes

You need some shims under the springs to change the pinion angle.

http://i810.photobucket.com/albums/z...4Runner048.jpg

In order for the flanges to be parallel, I'd have to rotate the pinion DOWN. Is this normal? I know for CV drivelines, you want the pinion point UP toward the flange.

With the snow I've had the chance to driven in 4wd a good bit. No noticable vibes up to 40mph.

No way. This is NOT the answer. It leads to too much caster, and even worse driveline angle. Not to mention that when the leafs droop, the tie-rod will hit the springs and rub.

I may be completely off here but shouldn't the pinion on the front diff point at the t-case? I mean.... well I don't have the words but back when I was doing SOA's on Scouts we'd cut the knuckles and rotate the axle so that the rear of the front diff was pointing almost right at the t-case output so that the front drive line was as straight as possible. Does that even make sense? That also helped with the 0 degree issue that Scouts had prior to 1980 (when they stopped making them) which made the driving like you were on freaking ice skates. We'd load it for -2 degrees for better road driving. I know that we're talking apples and oranges here with the Dana 44's I'm used to dealing with but pinion/drive line/angles are all the same when it comes to driving right?

Can you pull the axle and cut the knuckles and rotate the axle for a better angle or would it be less costly to buy a CV for the front?

Scotty,
That's about what I thought too. What do you think about the angles from the pictures? I know that they're a little hard to see.

The tie-rod is close to the spring, but i have a hi-pinion front third member, so it makes my drive line angles a little better than a low pinion third member. Would i be better off removing the pinion shims and bolting the springs right to the axle ?. My cousin installed the front axle and set it up for me, if its not right, let me know and i will remove the shims.

NEVER use shims on a front axle is my vote. Never had to, never will.

:wabbit2:

So if i remove the shims and bolt the axle directly to the springs the pinion angle will still be ok with the high pinion front third member ?.

If it were mine I wouldn't have put them in there in the first place. No need IMO.
Not even with a low pinion front third member. Especially with dual cases it is pointless.

:wabbit2:

It all depends on what sort of driveshaft you have, flanges parallel = u-joints, pinion pointing at t-case = CV joint:
- http://www.4crawler.com/4x4/ForSale/Shims.shtml#FAQ1

I always wondered why he put them in there. When the weather warms up i will remove them. I would do it now, but its about 8 degrees here with lots of snow here.

X2:welder: