Pinion angle

[72SB]

IMHO I find the tremec phone app comes up with different #'s each time. More because the phone case (better to use it without a case) you have to hold STEADY against the point you measure. A $5 magnetic analogue angle finder, for me, is more stable and "hands free" so the needle settles for an accurate reading. One option for getting trans tail angle is hold the angle finder against the flat front of damper as it is dead nits the same angle as engine/trans

Lowered truck often needs an angled shim on rear end to get DL angles back "within" spec and also flat shims between trans and rear mount. This is where using an angle finder tells you wtf "your" angles are and which direction the tail of trans needs to move and rear pinon

[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.

[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

[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.

[72SB]

OP

Are you sure this is a DL induced vibration??

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

[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.

[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.

[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...

[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?

[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

[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.