Pinion angle

[72SB]

drive shaft run out???

4:10's...that DS better be balanced dead nits and with a high RPM balancer....which few shops have

Tire balance good?
and rim bent or have run out?

[kwmech]

Originally Posted by tdangle

So are you guys saying that changing from a TH350 to a longer 7004R trans and having the front section of a 2 piece driveshaft will change the angles to the point that a vibration will occur.

Nope, that's why I asked how he had the driveshaft shortened. The clocking could be off or the front section-- if shortened by itself-- may not be in balance with the rear now

[pontiacvince]

Originally Posted by kwmech

When you had the front section shortened, did you take both pieces in to the shop or just the front piece? And did you pull the whole assembly out as a whole or pull the 2 pieces out separately?

I took the whole thing to a driveline shop. They shortened the front section and installed all new u-joints and carrier bearing. I can only assume they rebalanced it.

[tdangle]

Originally Posted by kwmech

Nope, that's why I asked how he had the driveshaft shortened. The clocking could be off or the front section-- if shortened by itself-- may not be in balance with the rear now

Actually it's been balanced twice (the entire assembly including carrier support). 1st time was when I had a 2004R. It didn't need a change in length but I had it completely rebuilt, new carrier bearing, U joints and balanced. 2nd time shortened and balanced (the entire assembly again) The shop has a high speed balancer setup and said it was good.

I ran it supported on jack stands without wheels, tires and brake drums. The vibration is still there. BTW: at 45 driveshaft speed is about 2K max. At 70 nice and smooth.

[kwmech]

Originally Posted by pontiacvince

I took the whole thing to a driveline shop. They shortened the front section and installed all new u-joints and carrier bearing. I can only assume they rebalanced it.

Yes everything should have been balanced as an assy----I assume you shoved it back in without taking it apart so everything still lines up?

I'd be looking at tires and rims--possible alignment--shocks, bushings not seated etc. Can you get us a picture of the rear with the d-line showing

[kaycee]

I used an app off play store seems to be pretty accurate and yes take the case off phone. I double and triple checked mine even bought a digital one to check it. I am a 1 piece shaft and installed a 700r4 that sits way low on stock crossmember 7*down on tail end and rear pinion was 2* up got the rear trans at 3*down should be good to go now.

[72SB]

OP

Are you sure this is a DL induced vibration??

Have you ruled out torque converter shutter? (most common at 45mph...)

[Ironangel]

Originally Posted by Lancialonnie

This post has definitely gotten complicated! I'm working through this with my 2-piece driveshaft now. I used 4 inch lowering springs and had the front driveshaft shortened when the 700r4 was installed. After a while I realized that there was no slip in the rear section and the driveshaft had destroyed the center bearing. I just had the CPP cross member and tubular trailing arms installed along with the poly center bearing and their rear slip driveshaft. Everything looks like it will work and now I just need to have the center yoke replaced, since there is metal missing where the c clips go, and get the unit balanced. I'm hoping this will do the trick and I won't have to do any angle measuring!

You should be good to go! Theres an app on these smarter than me phones that make your phone an angle finder..."Cheers!"

[pontiacvince]

Originally Posted by 72SB

OP

Are you sure this is a DL induced vibration??

Have you ruled out torque converter shutter? (most common at 45mph...)

No, not positive if it's the driveshaft. The torque converter is a brand new Hughes unit.

[72SB]

Hughes is a very good TC. what I run in other cars.

Trans fluid is a typical "shutter" problem...so assume you are running the right type. This assumes trans/TC shutter is even the issue. Just thought I would add hat to the ? list if the vibration was possibly not a DL angle issue or DS balance issue

[SCOTI]

Before changing a bunch of stuff, try re-using the previous rubber trans mount. There's been more than one complaint about vibrations after switching to Poly driveline mounts.

[tdangle]

to the OP, did you ever get this resolved?

[pontiacvince]

Originally Posted by tdangle

to the OP, did you ever get this resolved?

Not yet. I want to check the pinion angle before I do much of anything.

[tdangle]

Originally Posted by Ironangel

Actually, shortening the front shaft doesn't change the DS angle because the carrier bearing is in the same location. The fact that you went from rubber to polyurethane mounts may contribute to your feeling something now that you didn't with the rubber mounts. Also, did you have both shafts with the carrier bearing balanced when the shaft was shortened? I dont think any of the changes you've made would affect the
pinion angle enough to cause a vibration. On page 4-24 of the service manual it describes rotating the rear shaft 4 splines to the left side of the vehicle. Model CE31403 rotates only two splines to the left. That phases the rear shaft to the front shaft regardless of the pinion yoke position. You should have both front and rear shafts with the (preferably new) carrier bearing balanced assembled together with new u-joints at a DS shop.

What service manual are you referring to? I have the 1970 service book and don't see what you are referring to.

[kaycee]

If it helps any I used 1 of them ol school mechanical dials compared to my smart phone which I compared to a store bought digital which I compared to the tremec phone app and they all read different Couldnt hardly pinpoint the mechanical dial but the phone app seemed to be pretty close to it and the tremc toolbox app for the phone was way different reading. This was me squished under the car trying to get good readings . Good luck

[72MARIO]

I spent a great deal of time perfecting my driveline angles. Ended up being the polyurethane transmission and engine mounts. Back to rubber now and the vibration us gone
Poly has its place..in a race car.

[SCOTI]

Originally Posted by 72MARIO

I spent a great deal of time perfecting my driveline angles. Ended up being the polyurethane transmission and engine mounts. Back to rubber now and the vibration us gone
Poly has its place..in a race car.

I mentioned this above. Many overlook this as a possibility yet it's common. Easy enough to verify as well w/o requiring other changes & should be a 1st step IMO.

[pontiacvince]

My engine mounts are rubber. The trans mount is poly. Maybe that's it....

[SCOTI]

Originally Posted by pontiacvince

My engine mounts are rubber. The trans mount is poly. Maybe that's it....

Anything is possible & it's easy enough to verify.

[Ironangel]

Originally Posted by tdangle

So are you guys saying that changing from a TH350 to a longer 7004R trans and having the front section of a 2 piece driveshaft will change the angles to the point that a vibration will occur. I have a C20 totally stock suspension with rear leaf and 4.10 gears. Very noticeable vibration at ~45 to 50 MPH. Both shafts were rebalanced when shortened. Shimming Carrier bearing, 2 and 4 degree axle shims, many hours later and nothing really changes. Is not wheels, tires as these have been changed.

"NO!" Shortening the front shaft wont change the rear shaft angle. Having the two shafts phased together correctly can affect the balance, or a shop unaware of the phasing procedure for these older trucks may affect the balance. A two piece drive shaft needs to be phased correctly and the carrier bearing installed on the front shaft before balancing...I wonder about alot of these shops and the man doing the balancing, sometimes their age defies experience and knowledge...

[Ironangel]

Originally Posted by tdangle

What service manual are you referring to? I have the 1970 service book and don't see what you are referring to.

I have the 72 manual. Page 4-24, the 70 manual should have the same spline phasing procedure maybe not on the same page?