What diff ratio does a '79 have?

[Guest]

Is a '79 3.9 or 3.7? I know that '77 was 3.7, was it used from there up to '79, or for just one year? I've got an extra 3.7 and need to know if I'll be wasting my time by swapping.

Thanks.

 

[aeronca65t]

My '78 had a 3.7 for sure and I'd be about 95% sure that a '79 would also run a 3.7

My factory workshop lists all '75 to '79 cars as having the 3.9 ratio, but I know that is wrong.

 

[GeeBee1]

probably wasting your time, give the extra one to me :wink:

 

[mccalebr]

"The differential gear ratio was changed from 3.9:1 to 3.7:1 from GAN6-200001 (August 1977)..." [Horler - 'Original Sprite & Midget'; p.132; 'Rear Axle']

The information in Horler appears to coincide with the original dealer brochures on my web site (www.raysmg.com; 'Documentation' link). The Mk IV octagonal brochure (1-77) is the last one to list the 3.9 ratio...the remaining two brochures (1-78 and 9-78) both list it as 3.7.

Ray

 

[jcatnite]

Seriously,
There are several here that would like a crack at the 3.7 if you decide to sell it. The used ones are sought after since the usual suspects want an arm and a leg for a "rebuilt" one.
JC

 

[Guest]

Both need bearings. I'm just debating which one gets 'em. The "spare" has a small amount of surface rust on the ring face. I'd rather rebearing my original if it has 3.7. I wish I could find soemone with an old VB 3.55 they want to get rid of.

 

[jcatnite]

Yeah, a 3.55 would be sweet. Don't think there are many of those around. Seem to be pretty plentiful over the pond though. If the rear end needs rebuilt, it will still bring enough to pay for the rebuild on the one you have.
JC

 

[Hap Waldrop]

I got $425 for a 3.7 on Ebay one time, think about that the next time you see a $200 1977-on RB parts car lying around

 

[Trevor Jessie]

Yup, I bought a '79 parts car ... but it had been swapped to a 3.9 rear end. However, I still used plenty of other parts from it. And made money by the time I sold a bunch of the other bits.