rear gear 3.89

[Hodee]

Im wondering where I might source a 3.89 rear gear. Currently a late Ser V with a 4.22 . I know the drive shaft is a fine spline but not sure that matters which rear gear I use. Just to drop the highway rpms a bit. Im currently running very tall 15in tires which helps a lot. Just looking for a bit more. thanks

 

[Tim R]

If you are going to raise the gearing try and get a 3.7 if you can find one. These are rare but the difference out on the motorway is well worth it. Rootes tended to fit 3.7 to the high performance automatics and they are apparently more common in the U.S. than the U.K..
Tim R

 

[alpine_64]

Im wondering where I might source a 3.89 rear gear. Currently a late Ser V with a 4.22 . I know the drive shaft is a fine spline but not sure that matters which rear gear I use. Just to drop the highway rpms a bit. Im currently running very tall 15in tires which helps a lot. Just looking for a bit more. thanks

3.89 will help... But an overdrive would honestly be the best add.. @Jeff Howarth could probably sort that for you

 

[fordlandia]

Im wondering where I might source a 3.89 rear gear. Currently a late Ser V with a 4.22 . I know the drive shaft is a fine spline but not sure that matters which rear gear I use. Just to drop the highway rpms a bit. Im currently running very tall 15in tires which helps a lot. Just looking for a bit more. thanks

Hi, I have a spare differential that the prior owner of my Series V intended to install. Is there a part number identifying the rear gear ratio? I also have a complete overdrive transmission I plan on selling. I can take both to the United 40 so to avoid shipping. I only recently decided to part with them. Will be cleaning them up and taking photos. No clue yet on pricing.

Bill
Grand Rapids MI

 

[fordlandia]

Just found an old thread about spinning the rear end and measuring rotation to determine ratio. I'll try to determine the ratio that way. The PO said it was one of the two lower numerical differentials.

Bill

 

[RootesRooter]

If you are going to raise the gearing try and get a 3.7 if you can find one. These are rare but the difference out on the motorway is well worth it. Rootes tended to fit 3.7 to the high performance automatics and they are apparently more common in the U.S. than the U.K..
Tim R

In the U.S. 3.7's were fit to all Alpine GT fastbacks with automatics. Nothing noticeably 'high performance' about them.

 

[Tim R]

Bill, The ratio is stamped into the crown wheel. It will look like this....
Tim R

 

[RootesRooter]

One of the saddest days of my Alpine ownership was when the front oil seal went bad on my 3.70's, ending up with a shrieking monster that barely got me home.

Are new 3.70's still available from the Netherlands? The old rumor was that it was a very noisy unit. Any truth to that?

 

[alpine_64]

One of the saddest days of my Alpine ownership was when the front oil seal went bad on my 3.70's, ending up with a shrieking monster that barely got me home.

Are new 3.70's still available from the Netherlands? The old rumor was that it was a very noisy unit. Any truth to that?

Rootes post vintage did rerpo 3.70 for a while. There were mixed reviews on the whine... It may have been their mfg . It may have been people not setting them right when doing preload .... But either way I think it's now been a while since they were available

 

[Tim R]

My 3.7 is a genuine Rootes one, it is very quiet.
Tim R

 

[Hodee]

My 3.7 is a genuine Rootes one, it is very quiet.
Tim R

Thanks Tim. A great video. I'm assume that finding an entire "pumpkin" is much easier than changing the ring gear.

 

[Hodee]

Hi, I have a spare differential that the prior owner of my Series V intended to install. Is there a part number identifying the rear gear ratio? I also have a complete overdrive transmission I plan on selling. I can take both to the United 40 so to avoid shipping. I only recently decided to part with them. Will be cleaning them up and taking photos. No clue yet on pricing.

Bill
Grand Rapids MI

Thanks Bill, Texas is a long way to go for the United so i dont think I'l make it up. But you never know. Are you able to find out the ratio? And is it the entire pumpkin or just the ring gear?