3.89 differential

[65beam]

3:89

the original 3:70 gear sets are as quiet as a 3:89 as long as the ring gear bolts stay tight. i have original units in my series 4 and also in the wife's series 5. they are out of fastbacks that i had with the auto trans. the white fastback also has a 3:70 that i took out of a fastback that i parted a couple years ago.

 

[alpine_64]

They are a little noisy but I've grown used to it, and frankly it may be normal - I never owned one from new so really don't know what it should sound like. The ability to cruise at 85 mph in an Alpine makes it worth it.

What kind of RPM are they at 62mph oin OD?

 

[puff4]

What kind of RPM are they at 62mph in OD?

Kinda depends on the tire size. Assuming you have 165/80R13 tyres...

• With a 3.70 axle and OD you'd get 23.42 mph per 1000 rpm.
  At 60 mph you'd be doing 2561 rpm.

• With a 3.889 axle and OD you'd get 22.69 mph per 1000 rpm.
  At 60 mph you'd be doing 2692 rpm.

• With a 4.22 axle and OD you'd get 20.53 mph per 1000 rpm.
  At 60 mph you'd be doing 2923 rpm.

 

[agmason54]

3:89 differential

Chuck& Betsy,
I looked it up in Rootes Parts list Publication No.660092 page N2 part #5220523 and it turns out that I do have a 3:89 pumpkin still in a
SII..
B9108431 is the last Alpine to use course splined axels.The non OD donor's VIN# is B91161129.Call or PM me if you still need one...
Agm

 

[atallamcs]

Alpine diff

I have a 389, 25 spline in very good condition.
Bill

 

[AlpineII]

The Series II I wrecked last summer was B9108405. I never realized how close to the change it was.

 

[Mikeflbmer]

Super Minx Rear

I have the rear out of a 67 Super Minx that I parted years ago....It had an automatic tranny in it....Anybody know what the ratio should be? Is it a 389? or 370???? Also I have a posi rear out of an old Mazda rotary car that was raced....but I think a low gear....It has left and right anti sway bars...I believe will bolt in a sunbeam....Anybody need it? Mike