Drive-line vibration

[Bagged620bulletside]

Alright Guys I'm having a bit of an issue with my datsun. I am dropped about 5/5, Torsion bars Uncranked in the front and 3" Block, DJM 2 degree pinion shims and 1 leaf spring pulled out of my 3 leaf pack so i am rocking the main leaf and the overload. My problem is that at 20-30 45-55 I have a terrible shake i have tried My pinion shims both ways and doesn't seem to change the issue at all. Just wondering how the Lower static 720 guys have addressed this issue. I have had several static s10s but have never had a pinion angle problem this bad before.

 

[ggzilla]

Pinion shims change the pinion angle.

 

Have you changed the angle of the driveshaft to match?

 

If you have the two-shaft driveshaft, the carrier bearing must be lowered/raised to correspond the pinion angle and the the tranmission mount lowered/raised about 1/2 as much.

[Bagged620bulletside]

Pinion shims change the pinion angle.

 

Have you changed the angle of the driveshaft to match?

 

If you have the two-shaft driveshaft, the carrier bearing must be lowered/raised to correspond the pinion angle and the the tranmission mount lowered/raised about 1/2 as much.

 

Yea i know that pinion shims change the angle of the pinion that's why i have them in there hoping to fix the vibration issue but its not working, i have a 1 piece shaft. I didn't know if any of the other guys that are this low have done anything with transmission mount spacers or what not.

[flatcat19]

Check U-joints.

Check driveline balance.

 

Pinion shims should be installed so thickest part is at rear of car.

[datzenmike]

Keep in mind the the angle in should equal the angle out. In other words the angle formed by the front and rear driveshaft at the carrier bearing must equal the driveshaft to differential angle. Throwing shims at it without carefully measuring and setting these angles is like blindly putting wheel weights on a rim to balance it.

 

So on a two piece driveshaft this has to be looked at with the front possibly being affected by changes in the rear. The carrier bearing angle change may be so slight that the front is unaffected.

 

On my 710 I swapped a long tail 5 speed in and a shorter driveshaft, as well as lowering the rear at least 2". It had a loud hummmm when driving. I removed the driveshaft and held a compass from a geometry set vertically against the aluminum end of the transmission where the seal is and held a string with a washer as a plump bob. I did the same at the differential yoke. The transmission angle was much smaller than the rear end angle and the differential. Two ways to correct were to lower the tail on the transmission to equal the diff... but this would place it as the lowest point under the car and risk hitting it on bumps... (not sensible) or to lower the front of the yoke on the differential. By putting shims on the back side of the lowering blocks at the leaf springs. The axle is rotated downward at the front. I was lucky and used a 1/8" shim and the angles equaled on the first try.

 

Get paper and pencil and make a drawing and fill in the angled measured. Give it a little thought and the results are very worthwhile.

[ggzilla]

+1 what he said

 

If no angle change to the transmission mount then there should be no angle change made to the pinion.

 

But if no shims under pinion on a lowered/raised vehicle the u-joint angle might be too great which will cause terrible vibration. And if shims are added then the transmission/shaft angle must be changed to match.

[datzenmike]