Driveline vibration

[BB72CHEVKT]

I have a vibration in the drive line on my Suburban and after reading think it may be due to the pinion angle. I am running a 4'" rear spring with a two inch lowering block. The drive shaft was just shortened and balanced since I changed to a 700R4 tranny. It also has new u-joints and a new CPP billet carrier bearing. What is normally done to correct the pinion angle. Unfortunately the shop is 80 plus miles away and I need the burb back right away so I am looking at alternatives to returning to their shop. Do you think the problems are due to the long wheel base of the burb?

[SCOTI]

A couple of things that can be checked/verified @ home... Make sure u-joints are phased correctly. If not, that can cause vibrations. Also check the trans/driveline angle vs. pinion angle. They should be equal yet opposite or as close as possible.

[Painter D]

Originally Posted by SCOTI

A couple of things that can be checked/verified @ home... Make sure u-joints are phased correctly. If not, that can cause vibrations. Also check the trans/driveline angle vs. pinion angle. They should be equal yet opposite or as close as possible.

Agreed

I'd definitely check the U-joints first.
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[BB72CHEVKT]

How can I tell if the U-joints are phased correctly? Sorry for my ignorance. The rear end seems to be tilted up too much toward the burb floor is another reason for thinking pinion angle.

[SCOTI]

Originally Posted by BB72CHEVKT

How can I tell if the U-joints are phased correctly? Sorry for my ignorance. The rear end seems to be tilted up too much toward the burb floor is another reason for thinking pinion angle.

In phase....

[BB72CHEVKT]

I don't know if this will help but here are a few pics.

[SCOTI]

Only way to know is to measure w/an angle finder. Measure the differential pinion angle & the trans pan angle (easiest part of the motor/trans to measure).

[BB72CHEVKT]

Originally Posted by SCOTI

In phase....

Thanks that second pic help explain better. It looks real close. Is it either right or 180 out with no in between?

[SCOTI]

Originally Posted by BB72CHEVKT

Thanks that second pic help explain better. It looks real close. Is it either right or 180 out with no in between?

Correct.

It can be felt on a single shaft set-up so the 2pc set-up most likely multiplies the issue (I've never personally done the 2pc driveline on my trucks but have looked into possible concerns since my CC dually will be my 1st).

[BB72CHEVKT]

I am a little curious. Why do only some trucks need to shim the pinion and not others? I would think it would be an all or none situation.

[SCOTI]

Originally Posted by BB72CHEVKT

I am a little curious. Why do only some trucks need to shim the pinion and not others? I would think it would be an all or none situation.

Subjective... Some set-ups it's more noticed than others. A lwb, 2pc driveline, & OD trans would likely be more sensitive to vibration vs. say a lwb, 1pc, & a standard 1:1 3spd trans.

[wraprail]

you should measure your pinion angle at the pinion yoke (usually removing the driveshaft) and at the transmission tailshaft. Not the pan (although the pan rail would work)
You should be around 6 degrees( split evenly between the trans and diff 3 degrees each only opposite) total. You would probeley adjust the rear with taper shims under the lowering blocks and you can raise the trans mount (or lower the crossmember) to correct the trans.Maybe they got the wrong tranms crossmember?

One more thing, If you have an IPhone they have several angle finder apps that are free and work excelent

[BB72CHEVKT]

Originally Posted by wraprail

you should measure your pinion angle at the pinion yoke (usually removing the driveshaft) and at the transmission tailshaft. Not the pan (although the pan rail would work)
You should be around 6 degrees( split evenly between the trans and diff 3 degrees each only opposite) total. You would probeley adjust the rear with taper shims under the lowering blocks and you can raise the trans mount (or lower the crossmember) to correct the trans.Maybe they got the wrong tranms crossmember?

One more thing, If you have an IPhone they have several angle finder apps that are free and work excelent

I am running a CPP tranny crossmember that is supposed to accept the 700R4 and a CPP drop crossmember.

[SCOTI]

Originally Posted by BB72CHEVKT

I am running a CPP tranny crossmember that is supposed to accept the 700R4 and a CPP drop crossmember.

This might be part of the issue. These aren't needed until you do a fairly radical drop @ the spring. I'd try some pinion shims if the shaft phasing checks out correct....

http://www.stockcarproducts.com/

[BB72CHEVKT]

Originally Posted by SCOTI

This might be part of the issue. These aren't needed until you do a fairly radical drop @ the spring. I'd try some pinion shims if the shaft phasing checks out correct....

http://www.stockcarproducts.com/

Yes phasing is correct. It is a drop trailing arm crossmember.