About to pull the trigger on 3:42

[tobyp]

The only thing that concerns me is the highway RPMs. I have a communte that I drive 23 miles one way to work. I cruise along at 70 mph at 2200 RPM. I currently have a highway gear 2:43 with a th350. How bad would the rpms scream at 65-70 mph?

 

[jmt455]

You will be turning approximately 3200RPM at 70 MPH.

I've also been thinking about a gear set change.
If I was ultimately going to install an OD trans (200-4R or 700-R4), the 3.42 would be a nice choice.

If you are planning to stick with a non-OD trans, you might also want to consider a 3.23 gear. At 70, you will be turning approximately 3025RPM.

 

[DRIVEN]

http://www.angelfire.com/fl/procrastination/rear.html

 

[Longroof79]

Honestly, you're not going to like it unless you go with an OD trans, or have 3.08's put in the rear. Especially for a car you commute with. And again, this is my opinion and my experience using 3.42 gears and TH350 trans.
Besides your mileage being cut, it gets nerve wracking hearing the engine buzz away at 3000+ rpm.
The 3.08's are more tolerable, but I'd still prefer an overdrive trans.

 

[DRIVEN]

By using the RPM calculator I posted I found that my car will have the exact same cruise RPM with a 200-4R/3.42 as the original TH200/2.29. It just has way quicker acceleration. It's a fun tool for finding the right combination without spending money on parts you end up not liking.

 

[tobyp]

Thanks for the replies. I have a hard time finding the 8.5" rear I am looking for with also finding a 200r4 without taking part of my leg and my arm off. What a damn addiction!

 

[dogsht]

Toby You don't need the 8.5 to upgrade to the 200-4R. A 7.5/7.625 would be a perfect match for that Buick 350. Its not like you have a 455 with slicks & a transbrake. Down the road if you want to upgrade it with 28 spline axels, posi & support cover it would handle all that 350 can throw at it even at the track.

Lonnie Diers from http://www.extremautomatics.com from right there in Cincinnati built two 200-4Rs for me with good results. If money forces you to stay with the ole 3 speed get a 3.08 its a much better compromise. Most of the acceleration and still a nice driver. But if you plan to step up to the 200-4R anyway why not wait on the gear and buy once instead of twice. With Extremeautomatics you don't even need a core you could just order and drive over and pick it up when you and it is ready. 8)

Edit: In fact if you go 200-4R you could go 3.73 and still have a final drive ratio of 2.49 almost exactly what you have to cruise on the highway now only with dramatically better acceleration. Plus the benefits of a lock up torque converter.

 

[tobyp]

Toby You don't need the 8.5 to upgrade to the 200-4R. A 7.5/7.625 would be a perfect match for that Buick 350. Its not like you have a 455 with slicks & a transbrake. Down the road if you want to upgrade it with 28 spline axels, posi & support cover it would handle all that 350 can throw at it even at the track.

Lonnie Diers from http://www.extremautomatics.com from right there in Cincinnati built two 200-4Rs for me with good results. If money forces you to stay with the ole 3 speed get a 3.08 its a much better compromise. Most of the acceleration and still a nice driver. But if you plan to step up to the 200-4R anyway why not wait on the gear and buy once instead of twice. With Extremeautomatics you don't even need a core you could just order and drive over and pick it up when you and it is ready. 8)

Edit: In fact if you go 200-4R you could go 3.73 and still have a final drive ratio of 2.49 almost exactly what you have to cruise on the highway now only with dramatically better acceleration. Plus the benefits of a lock up torque converter.

Yea,

I am in touch with Lonnie right now. Since I work for LKQ and he knows Brian Weaver at Gbody and he needs some parts :wink: He and I are going to start working on a plan.

 

[dogsht]

Very cool! 8)

 

[tobyp]

Very cool! 8)

heck,

Look me up if you ever need anything as well, I'm only down the road from you a bit.