Overdrive: Who doesn't have it?

[lukeball]

I am hoping to upgrade to a B20 (2100cc B20F head ported) and I have also considered adding an overdrive, but it just doesn't seem worth while installing it.

I want to know who DOESN'T have overdrive. I am not looking to drive my car on the highway very often, and if I do it will be for short distances like <10 miles. Is it ok to drive these engines at sustained rpms along the highway or does it damage the engine? My neighbors think so, but they only know large displacement V8s.

Currently, I have the 4.56 diff, but I have thought about 4.10 or 3.90. At 70 mph I would be at 4292 rpm. Other than noise, is it ok to cruise at this rpm? I have noticed that a few people don't have it, but do you drive on the highway?

[940_Turbo]

It won't damage the engine, it may give you tinnitus however.

[lukeball]

Originally Posted by 940_Turbo

It won't damage the engine, it may give you tinnitus however.

I already have tinnitus from shooting automatic weapons without earplugs (it was a bad idea, but after 100 rounds, whats the big deal?).

Thanks.

[Alf ista]

I have a B20 with no overdrive. Being a 1970 car I think it has a 4.1 rear diff. No problems whatsoever, these engines are so well engineered. It is noisy though, and that seems to be the only real drawback.

[tom-madbiker]

yep at 95 with a 4.6 diff even with an overdrive i have to shout at the passenger

[heckflosse]

Originally Posted by tom-madbiker

yep at 95 with a 4.6 diff even with an overdrive i have to shout at the passenger

If you can get one, fit it !

[Derek UK]

Originally Posted by Alf ista

I have a B20 with no overdrive. Being a 1970 car I think it has a 4.1 rear diff. No problems whatsoever, these engines are so well engineered. It is noisy though, and that seems to be the only real drawback.

It's possible that you have the 4.30:1 diff. Once you have overdrive you'll wonder how you ever managed without it. You certainly won't want to go back. Factory OD cars have the low back axle so don't get the quiet cruise advantages of fitting it to a car with the higher ratio back axle.
For Luke with his 4.56 axle and a built B20 adding the OD will allow it to be both a tyre smoker or a cruiser. Having a nicer car to cruise in might tempt him to go further afield. Gas mileage will be up too. Nice even at cheap USA gas prices.

[Alf ista]

Originally Posted by Derek UK

It's possible that you have the 4.30:1 diff. Once you have overdrive you'll wonder how you ever managed without it. You certainly won't want to go back. Factory OD cars have the low back axle so don't get the quiet cruise advantages of fitting it to a car with the higher ratio back axle.

Thanks Derek, but I must look that up. I was under the impression that since the last cars didnt have an option of overdrive then they had the 4.1 diff. Must find out. Either way I would love an overdrive so if someone wants to give me a Christmas present.... I will forward my address! Ooh, and a nice set of those wide wheels from Brookhouse too please....