This problem did not seem to exist before I installed the 9". Its really bad on deacclerating but it also exits above 70mph. I thought it was the tailhousing bushing on the tremec.. but after replacing it, it is not really any better. The lower control arms are adjustable. But, since the torque arm (a JEGs one) has no adjustment, I really cant change the pinion angle. I think I will need to get some type of adjustment in the torque arm before I can get this reduced.. any one have similar experiences?

 

With out knowing more it`s hard to say but I`m thinking pinion angle????

 

9" moves the driveshaft u-joints lower than a stock 10 bolt, could be the driveshaft due to the increased u-joint angles

 

but I think its something to do with alignment because it gets so bad when the rearend changes when I let off.

 

check pinion angle then report back.

 

I have confirmed there is no where near 1+ degree downangle. But all aftermarkets (spohn and bmr) are telling me there is no solution for a 9" with a tremec to get an adjustable pinion angle.


What solutions have been used by those here to adjust pinion angle with a tremec and 9" combination?

 

jegs sells an an adjustable torque arm that mounts to the floorpan that would work for you.

 

You can adjust the pinion angle at the rear by changing the control arms. I wouldn't go too far with that, since it also changes the wheelbase; but I'd think that just a little bit, like less than ¼", might really help.

You can lower the rear of the trans by stacking shims between the crossmember and the frame, so that the angle between the drive shaft and the trans is about the same as that between the drive shaft and the rear. If those angles differ very much, it will vibrate from the drive shaft shuffling front to rear along its length as it spins.

I can't imagine what a Tremec, or a 9", would do that would make either of those adjustments ineffective.

 

The existing jegs torque arm I have is the non-adjustable one. They said I cant really purchase the hardware to turn it into an adjustable one. I guess the only option on that deal is purchase an entire other one.

I tried to adjust the lower CAs, but I really cant get even one more turn on the heim joints to add negative Pinion angle. Even adding one turn makes it where I cant align it up on the otherside.

Currently, the tremec is about straight with the rearend - there is about 0 degrees and I cant raise the trans anymore because it is touching on the bottom of the car.

 

I'd expect, with a 9", you'd already have TOO MUCH negative pinion angle; since the pinion is located lower in the housing. ??? That's what usually happens anyway.

When you say you can't line it up on the other side, why? are the LCAs already fully extended, or what?

I'm just having a hard time imagining how it could be THAT FAR off, in the direction you seem to be saying that it's off. I can see how the trans could be tight in the tunnel, but the parts about the rear sound kind of odd.

 

The LCAs are not fully extended, but since the Jegs TA is hard mounted and is closer to the rearend than a normal TA, it just pivots in the center. One side goes forward, the other back. There is basically no ability to "lengthen" the distance between the Trans and rearend, effectively limiting the pinion angle to what it is. I will take a pic of the angle finder on the car this afternoon.

 

OK, makes sense...

Whose bracket is on the 9"? Any way to modify that? If it bolts onto the chunk studs, any way to use washers or something under it, to tweek the angle it sits at? Could you drill new holes in the torque arm to attach to it?

Would you be willing/able to cut and thread the torque arm at the rear, and put 2 rod ends in it?

 

Well, it does not bolt to the pumpkin studs. It basically mounts like a standard TA (the housing is a moser) and has a bracket for the TA. Here is a pic of the TA from jegs
JEGS High Performance - Jegster Camaro/Firebird Torque Arm (click on view image)
I tried to get a couple of pics of the pinion angle with it jacked up in back (with the plan of subtracing the driveshaft angle which appears to be about 0 when jacked - from the pinion angle which appears to be about -3.5 to give me the effective pinion angle), but with the angle finder attached to the pinion support which I dont think is flat, im not sure Im getting an accurate reading. I found a local guy who had said he would maybe mount some heim joints in the non-adjustable one and I sent him the jegs pics of both the TAs, but have not heard back yet. I guess its closer to neg 2.5ish than I thought, which is disappointing bc that would indicate this might not fix it, but I guess I could start with some washers in the top bolt. Certainly would be easier and cheaper than another TA (which might have minimal benefit). thanks for the suggestion.

edit
But now that I think about it, I would need to put the washers on the mount that wraps around the centersection. .. that might be a challange.. .but I will give it a shot.

 

I sent a note to tremec ( Transmission Technologies Corporation (TTC) ), to ask them about a torque arm mount on a tremec. They appear to have forwarded the note to one of their sales outlets. Whoever answered the e-mail, offered a suggestion to rotate the driveshaft 90 degrees .. I guess the individual does not spend too much time under a car...

>>> "Jeff Chytil" < > 9/29/2006 8:43 AM >>>
Jimmy,
Mark with a paint pen where your drive shaft is bolted to the
rear end. Try unbolting the drive shaft and re-bolting the drive shaft a
quarter turn, (90 degrees). See if this makes a difference, or better or
worse. The two through holes and the threaded hole on the drivers side
are for a torque arm provision.

 

i think he means 180 degrees, and sometimes that will stop vibrations

 

He seems to be implying that the rearend yoke is a slip fit and should be rotated. Im not sure where thats from.. :/