429 CJ Mustang/Cougar

429 CJ Mustang/Cougar

3.91 Traction Lok "N" Case Paint Markings

The pictures above are from an original '71 429 SCJ Mach 1 with a 3.91:1 Traction Lok. Note the following;

• The yellow paint dab by the "N"

• The blue color on the yoke and pinion support

• A red paint daub on the bottom side of the yoke

• The number "7" and "0" on the driver's side of the case

The pictures below are from a '71 Boss 351 also with the 3.91 Traction Lok. Note it also has the yellow paint dab above the "N".

  
The pictures below show additional paint marks found on the Boss 351 3.91 Traction Lok "N" Case.

Yellow dab on bottom of case.	In the photo at left, note the pink paint mark on yoke. The photo at right shows this same pink mark  looking from case towards yoke.
There is an additional pink paint mark and white dot on the opposite side of yoke. The picture at left shows an overview and a closeup in the photo at right.

Traction Lock Unit 

Detroit Locker

Detroit Locker

Differential

Axle Tube

31 Spline Axle with 3 holes. Note: The three hole rule is only to be used for small and mid size cars from 1971 and earlier.

28 Spline Axle with 1 concave hole.

N Case Carrier

Daytona Support

Detailed "N" Cases

9"  Rear End Housing

Pinion Snubber

Differential Yoke for N Cases with Daytona Pinion Support

28 Spline          28 compared to 31             31 Spline

AXLES

The picture above shows a 28 spline axle. You can spot a 28 spline by the large concave hole on the end of each shaft. The other photo shows the more desirable 31 spline axle. These can be identified by the flat surface with 3 dimples on the end of each shaft. Note: The three hole rule is only to be used for small and mid size cars from 1971 and earlier.

Traction Lok

There are two different Traction Lok unit designs shown above. If you look closely, the earlier design version at left has four silver dollar size holes at the 3, 6, 9, and 12 o'clock positions. These four deep holes, machined into the  inside of the cast iron cover, act as stress risers and significantly weaken the unit. The later design shown above right, is stronger because it does not have these 4 holes.

Both of the Traction Lok designs shown above have a common weak point when used in very high horsepower applications. The cast iron cover can fracture around the perimeter at a thin point in the casting. The photo below shows the same unit with the broken piece in place (at left) and removed (at right). The Traction Lok is still OK for the street, but not high powered racing.