Why do the swap if the car already has an 8 3/4 in it?
The answers:
- I recently changed jobs and the new work site is a "cross town shuffle", no freeway time.
- I recently picked-up a 3.31 ratio and wanted to give it a try.
- The unit is an early 60's 8 1/4 "drop-out", that fits right into the 8 3/4 housing already in the car!
So it's gear swap time... 2.94 pumpkin comes out and the 3.31 goes in.
Here are the two center sections, side-by-side, as you can see... the case is the same.
Note how the ring gear bolts to the carrier, fewer bolts that thread into a inner flange 'lip'... this keeps the ring gear thin, thinner then the 2.94's ring gear.
The carrier itself is pretty small but the spider and side gears are a decent size... way bigger then what you see in a 7 1/4. What makes this sweet is that the 30 spline 8 3/4 axle shafts plug right in.
This photo show how "hollow looking" the smaller parts look in that 741 case.
The good news... the unit is a good 15 lbs lighter then the 2.94 that came out.
My 63 FSM shows the 8 1/4 drop-out listed with the 8 3/4 service procedures. It lists the unit as "for 6 cylinder cars" and shows the 3.31 and a 2.93 ratio. I am amazed that Mopar would do a smaller gear size for the lower powered vehicles... was it done to reduce HP consumption or to save some $$$... it just does not make much sense. ( or cents as the case may be)
Anyway... I like this unit and the ratio, it works well for my around town driving. One other nice thing, this gear set is noise-free, not a sound out of it. No gear howl, no bearing noise... I can almost hear the gear oil splashing around inside
but nothing else.I need to beat on it a bit to see if the unit give me any trouble.
DD
