Questions about adding overdrive

[George Coleman]

Jim what is the finial ratio of the OD trans? Scotts post said 80mph at 3000rpm has got me stumped?

 

[Series3Scott]

Scott, Are you using a OD with the 3.70 gear?

Yes - I replaced the stock 3.89 with a new 3.70 set from Rootes Post Vintage Spares. Coupled with my OD it makes for a sweet cruise at high speeds on the highway. I'm using 165/80 R13 radials.

 

[RootesRich]

Yes - I replaced the stock 3.89 with a new 3.70 set from Rootes Post Vintage Spares. Coupled with my OD it makes for a sweet cruise at high speeds on the highway. I'm using 165/80 R13 radials.

Scott, did you have your speedo recalibrated for the rear end change? I'm swapping my 4:22 with OD to a 3.89 and to have MoMa rebuild and recalibrate my speedo cost $230. Granted their work is superb, customer service is great and turn around time is fast, but their price has going up significantly the past few years!

 

[alpine_64]

I think the alpine with OD and 3.89 was 3.31:1 in top IIRC so with a 3.70 you would be really crusing.

 

[Series3Scott]

Scott, did you have your speedo recalibrated for the rear end change? I'm swapping my 4:22 with OD to a 3.89 and to have MoMa rebuild and recalibrate my speedo cost $230. Granted their work is superb, customer service is great and turn around time is fast, but their price has going up significantly the past few years!

Yes - Speedograph Richfield in the UK did mine. They sent me a worksheet to fill out giving them all the specs of my car and from that they calibrated my speedo. Cost was 53 pounds back in 2003.

 

[George Coleman]

Just looking at the gearing and with the 3.70 with the OD your finial drive ratio should be 2.97 at the rear, at 80 mph you should be turning 3756rpm thats with 13" tires, just a thought. My final drive with the 3.70 gear and the Toyota 5 speed is 3.18, so at 80 mph my tach reads 4020 rpm.

 

[Series3Scott]

Just looking at the gearing and with the 3.70 with the OD your finial drive ratio should be 2.97 at the rear, at 80 mph you should be turning 3756rpm thats with 13" tires, just a thought. My final drive with the 3.70 gear and the Toyota 5 speed is 3.18, so at 80 mph my tach reads 4020 rpm.

Let's go back to my original email. I said "going close to 80". I'll have the car out this weekend and do EXACTLY 80 and report back on what the tach says.

The main point of my submission was that the 3.70 rear end with OD is a fantastic combination for high speed cruising.

 

[George Coleman]

Thats right its all in the driveablity of the car I just thought that I had missed out at a better gear setup

 

[lgurley]

3.70

While you are waiting on Dellow and I know they are in no hurry, You can install a 3.70 gear with your stock trans. this will give you a good highway speed. I installed the 3.70 gear and it worked well then I added the 5 speed it made it better.

I am installing the 3.70 and an O.D. transmission next week. I think I will have to send the drive shaft out to be shortened. (right?)
I still want the 5 speed. I have more Alpines to get back on the road.

 

[65beam]

overdrive

george,
keep in mind that not all overdrives are the same as what was stock for an alpine.when i had mine rebuilt,the person doing it made some changes to the od in order to lower my rpm's even more.