NightmareTA

iTrader: (20)

Hey guys. I have a BMR adjustable torque arm and T56 transmission crossmember in my 86 trans am. I was recently underneath it getting ready to weld my subframe connectors in and I noticed that the driveshaft angle is out of whack. The car is on ramps in the front and has jack stands under the axle, so it is sitting like it would on the ground. My driveshaft actually has an upward angle from the back of the transmission to the axle. Every other car I have ever seen, the driveshaft has a downward angle to the axle. I'm really stumped on how to correct this since I don't even think the torque arm has enough adjustment to make that big of a difference. There are also a series of holes on the tranny crossmember to adjust where the TA bushing sits. I have it set to about the middle currently but am wondering if this needs adjustment??

Anybody with a similar setup that can give me any tips on how to set these, or a ballpark on where they are supposed to be? My car is also lowered 1 3/4" but I've seen plenty of lowered cars without this problem.

Somebody please help a brother out!

01ssreda4

iTrader: (96)

None of what you described will change the DS angle much. Whether the shaft goes up or down is really more a product of how high and low the trans tail to rear end relationship is. Most f body cars have near level driveshafts. Trucks and such will have a pronounced downward slope. Nature of the vehicle design.

NightmareTA

iTrader: (20)

The car drives smooth, and I've had it up to about 135 mph and felt no vibrations, but adjusting pinion angle and all that is new to me so I'm not sure if I have it at the "optimal" position. By eyeballing the rear axle, it seems like the pinion is pointing upwards a bit, where as I would think it should be level with the ground instead. I'm gonna call BMR (since they're the experts lol) and see if they can give me some insight on it. Thanks for the reply btw.

lowprofile

iTrader: (3)

Why eyeball it? Borrow an angle finder or buy one from harbor freight for $4.99. Put it on the back of drive shaft, then base of torque arm. Add them together and see what what your angle is. Adjust as needed...adjustable TA is (almost) worthless without an angle finder.

Edit: Would imagine BMR would be able to help determine angle for your application

01ssreda4

iTrader: (96)

No vibrations? I'd say you're fine and leave well enough alone.

BMR Sales2

iTrader: (40)

I agree 100% with this. The main function of adjusting the pinion angle is to get rid of any unwanted vibration from incorrect angle, it really doesn't affect performance too much at all.

Where you mount the front of the torque arm on the crossmember does change the performance so that could be something you want to play with. Generally the 3rd or 4th hole from the bottom is close to the factory location. The higher you mount the front of the torque arm the harder it will hit the tire but the shorter it will carry the power out, the lower you mount the torque arm the softer it will hit the tires but the further it will carry the power out.

NightmareTA

iTrader: (20)

Thank you for the reply. Very happy with all of your products so far, and my car has quite a few of them!

Also what do you mean by "hit's the tire hard, but doesn't carry the power out" and vice versa? Do you mean it will launch hard but lose some top end? It's a "spirited" street car so really just looking for the best setup on the street.

BMR Sales2

iTrader: (40)

The more energy (harder) you hit the tire with the less energy it has to push the car. It is kind of a give and take deal and every car has its happy spot depending on tires, temperature, traction, etc, etc. Moving the front of the torque arm up and down will adjust the instant center and also affect how fast the torque arm reacts which is why mounting it high hits the tire harder and lower hits it softer. If I were you I would leave it where it is at since you are going to really just be playing around on the street. If you decide to put some sticky tires on it and take it to the track it may be beneficial to play with it some but for the time being I would just leave it alone.