Spohn 399 User Manual

Spohn Performance, Inc.

494 E Lincoln Ave Myerstown, PA 17067

1-888-365-6064 www.spohn.net

Full Length Transmission Mounted Adjustable Torque Arm

Part # 399 – 1982-2002 GM F-Body

USE OF THIS PRODUCT IS ACCEPTANCE OF SELLER’S DISCLAIMER OF WARRANTY!

By their very nature, competition components are cons ta ntly pus he d to their limi ts . While o ur com po ne nts are
designed to withstand intense race conditions, it is impossible to control the quality of installa tio n or the varying
conditions in which they are used. It is for this reason that absolutely no warranty or guarantee is either written or
implied. Neither the seller nor the manuf ac ture r wi ll be liable for any loss, damage, or injury – direct or indirect –
arising from the use of or inability to determine the us e of any prod uc t. Befo re us ing, the user should determine
the suitability of the product for its intend e d use , and the user shall ass ume all res po ns ibility in connection
therewith. Spohn Performance, Inc . makes no guara nte e as to the legal ity fo r any spe c ific class. Spohn
Performance, Inc. makes no claims, nor does it intend its products to be used in street driven vehicles. Spohn
Performance, Inc. reserves the right to make changes in desig n or add to or improve on their pr oduc t witho ut
incurring any obligation to install the same on prod uc t prev ious ly manufactured. The Buyer agrees to indemnify
and hold Spohn Performance, Inc. harmles s from any clai m, actio n or demand aris ing out of or inci dent to the
Buyer’s installation or use of product

s purchased from Spohn Performance, Inc.

Instructions

1. Raise car and support with jack stands under frame allowing rear suspension to fall to it's
furthest position.

2. Remove both long bolts that attach the factory torque arm to the rear end.

3. Remove all three bolts that hold the torque arm front mount to the transmission and
remove the entire torque arm and front mount assembly. Some cars require lowering the
transmission crossmember in order to remove the bracket.

4. Separate the two halves of the factory clamshell front mount and remove from torque
arm.

5. The factory mount requires minimal modification to accept the supplied polyurethane
bushing. Locate the four rivets that attach the rubber bonded metal to the brackets and drill
out or grind off the factory rivets to remove the r ubber portion. Leave the outer half of the
clamshell mount off and reinstall the half that bolts to the transmission. Tighten.

6. Place the polyurethane bushing onto the mounted half and install outer half but leave

the top bolt loose.

7. Lube the polyuret hane bushing and then slide the torque arm in through the bushing.
Positioning the rear bracket over the rear end may require turning the torque arm adjuster
to get the proper bracket angle. Note: All jam nuts and rear bracket cross bolts must be
loose to turn adjuster. The rear end may also need to be levered into the proper position to
slide the torque arm bracket over it. Once this is achieved, slide the factory bolts in through
the top and tighten to 100 ft/lbs.

8. Tighten front mounting bolts to snug bushing.

1

9. Once pinion angle has been set, tighten all jam nuts and rear bracket bolts.
Note: Before adjusting your pinion angle, you must first loosen the two bo lts that secure

the two rear solid rod ends to the rear-housing mount. This allows the torq ue arm the ability
to swivel up or down as you adjust the pinion angle. If you do not loosen these two bolts
the assembly will bind and you will not be able to a d just the pinion angle. After setting the
desired pinion angle, retighten thes e tw o bolts.

Ford 9” Rears: For those running a Ford 9” rear - You will notice that the rear mounting
bracket of the torque arm has two sets of mounting holes. On the 9” rear you want to use
the set of mounting holes that are towards the driver’s side of the car. On a stock rear or
12-bolt rear, you would use the set of mounting holes towards the passenger’s side of the
car. The reason for this is that on a 9” rear, due to the larger center section, the torque arm
mount on the rear is actually 1” further to the driver’s side of the car compared to the OEM
rear. Using the set of holes towards the driver’s side of the car in our rear mounting bracket
will move the torque arm back to the OEM location and line it straight up with the front
mount. If your 9” rear is equipped with a nodular (large ribbed) center section, it may be
necessary to grind away part of the rib so it does not interfere with the torque arm’s rear
mounting bracket.

2

Setting Pinion A ngle

There are two an gle s to deal with:

1) Driveshaft angle

2) Pinion angle
You subtract pin ion angle from drives haft angle to get TRUE pinion angle
Here's how you do it:
First, had you m easured your stock driv e s haft angle and pinion angle before you r emoved your stock

torque arm, you would have calculated a 0 deg. TRUE pin ion angle. This is how a ll c ars come from the
factory.

Using an angle finder place it on the underside of the driveshaf t and record the angle indicated.
Next, place the angle finder under the flat surface where the torque arm mounts to the rear end (this

surface is parallel with the pinion s haft) and record the angle indicated.
Record both angle s from the driver’s side of the car. On th e d r iveshaft anything to the left of 0 is

positive, on the rear end anything to the right of 0 is negative.
Subtract the pinion angle from the dr iveshaft angle. The result is "TRUE Pinion Angle".
In order to apply preload you need negative TRUE p inion angle. Adjust the torque arm so that the

front of the pinion goes down; con tinue to check each an g le until the pinion angle is m or e degrees
down than the driveshaft angle.

We recommend –1 degrees on a m ildly m odif ied daily driven car. For h igh horsepower applications we
have gotten the best r e s ults with –2 to –3 degrees. There is no reason to run more negativ e th en
that, it will actually hurt your per formance becaus e it will induce driveline bind.

You don't want to drive around with your suspension preloaded all the time, it' s a lot of unnec es sary
binding on the u-joints and suspension. It should only be used when racing.

Here's a tip. Whe n adjusting for you r TRUE pinion angle, count the number of flats (or the 1/6 of a
turn) as you turn the adjusting nut, to know how many it tak es to adjust 1 degree of nega tiv e T RUE
pinion angle and in what direction (c loc kwise, or counter-clockwise). O nce you know that, then
adjusting the arm at the track or before a r ace will take almost no time, and no angle finder will be
needed.

Adjusting your Spohn Torque Arm: You adjust the pinion angle by turning the pinion angle
adjuster, (located at the rear of the lower torque arm tu be ) e ither clockwise or c ounter-clockwise. As
you turn the adju ster you will see the pinion nose of the rea r housing moving up/down. Moving the
rear housing's pinion nose down will g ive you more of a neg a tive pinion angle degree, and up will give
you more of a positive pinion angle degree.

You will quickly le a r n that it does not take m a ny turns to adjust the angle by several degrees, so go
slowly and chec k your angles often.

3