Oldracerjones

I have 3.91 gears in my 70 442 and while I love the acceleration speed I'm not so crazy about the 3,000 RPM at 60MPH going done the road. I don't drive the car daily but want to be able to go to shows and such more than a few miles from the house.

Anybody had to make this choice before? Did it do what you expected it too?

69ishHoliday

A trailer and a Silverado.

oldsmobiledave

Two options are put a taller tire on the back or install 3.42s into your existing carrier. Swapping in a OD trans is a 3rd option.


What size rear tire do you have on the car now? 3000 rpm @ 60 mph with 3.91 gears indicates that you have a very short 26.3" tall tire on the car.

69ishHoliday

http://www.discounttire.com/dtcs/infoTireMath.dos

This seems a good calculator that Oldcutlass posted for me when I was weighing options.

And this is the other one,

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

Lonestar

I also have 3.91's and there a bit steep for the distances we're used to traveling in Texas. If you have a Turbo 400 auto in your car the Gear Vendor overdrive unit is a good choice... a bit pricey but will handle up to 800hp with no worries. As others have posted, taller rear tires, changing the ring & pinion, an overdrive tranny, or a trailer round out your options.

oldcutlass

X2 with Dave, you have options. You also have to weigh the mod cost against the perceived inconvenience of going slower and the gas savings difference long term based on annual miles traveled.

nj_cutlass72

So for higher gear ratio, ie 3.42, taller tire will maintain lower rpm in higher speed but who wants that...

At cruising speeds the transmission gear ratio is 1.00 for th400 and muncie's, is there a significant difference in having an extra gear with muncie 4 speeds vs th400 for highway driving?

oldcutlass

The final drive ratio on a Muncie is also 1:00, no difference.

monzaz

Yes this is wrong info if you think 4 speed manual has different final gear. 4 speed was better in racing as the gear shift were tighter to get the car through each gear and pull better

As stated still 1 to 1 with the rear end ratio once you hit 4th gear.

Over Drive trans built strong is the only way right now with the 12 bolt Olds rear. 700R4 or 200R4 or retro Electronic 4L80 in the rear which are real strong. Might need mid plate to doe this . Jim

Nilsson

It is just RPM's, what does it hurt other than crappy gas mileage? I have A 4-speed car with 3:91 and drive it anywhere I want to go. I admit I don't travel real long distances but wouldn't hesitate too if I really wanted. Your situation may be different living in TX. What distances do you need to travel to attend car shows?

2blu442

Since your car is a clone I'd consider an overdrive transmission. I've got a 1970 442 that a previous owner swapped a chevy 12 bolt into. It has aftermarket 4.10 gears. In 1995 I found a ZF 6 speed from a 1991 corvette at a reasonable price and with the help of friends modified the Olds bellhousing to fit. There are a lot more overdrive transmissions on the market now so I wouldn't go with the ZF again, but the overdrive made it much more comfortable on the highway. I also got about 17 mpg on the freeway although the quality of gas was likely better back then and may have had something to do with it. The biggest downside was that I had to hack the transmission tunnel much more than I wanted to make the shifter fit. This car was my daily driver through the 1990's. John

Fun71

My engine is turning 3200-3400 RPM at highway speeds and I drive 35 miles each way to the monthly car club meeting/show and 100 or more miles each way to shows in other cities. The only issue I have is that during the summer with 100+ temps and the AC on the coolant temp gets up to 210 or so. If I slow down and bring the RPM below 3000 the temp comes down to 190 and I can cruise all day.

As others have posted, taller rear tires is a good way to bring down your cruise RPM, if you are really concerned about it. I'm not.

Koda

My 72 came with a 2.73 posi. No, it's no off the line sprinter, but it will go all day from 50 to 80 no issue. Downshifting to pass at highway speeds is an absolute joy.

My 67 has 3.08 posi, and I am not planning on changing it. I do more highway driving than drag racing. If I ever do get a drag car, that, of course, is different.

Oldracerjones

What size tires,are you running? I have the OEM size wheels and tires.

Oldracerjones

I don't mind driving it at high RPM it just is not normal to me anymore. My new cars all run at 2,000 rpm at 70, very quite.

The good guys nationals in two weeks is only 45 miles from the house but I want to go to the North Texas Olds Club get together in Granbury, TX in April. It's about 2 hours from my house.

With the car being new, just have to get used to it and it needs to prove to me it's reliable. I think any real long distance I'll just trailer and drive locally.
Thanks for the input.

oldcutlass

Cruise at 60-65 and don't worry about people passing you. Look forward to seeing you in April.

Fun71

Details are in my sig line below. 245-60-14s on factory SSII wheels. Tires are VERY short at ~25" tall, which combined with the 3.23 gears makes the effective final drive ratio fairly low.

I had the original 2.56 axle back on the car for a while and I swear to you the engine seemed much happier at the higher RPM on the highway (2800-3000) than it did at ~2200 RPM with that axle.

Agreed. That's essentially what I meant by reducing the RPM to below 3000, which would equate to 60 MPH or so. Just hang out in the right lane and wave back at all the folks who will be admiring your ride as they pass by.

Lonestar

Some very good info in the link below addressing optional transmissions and the pros and cons of each vs a true overdrive unit.


http://www.gearvendors.com/

Oldracerjones

Great link thanks.

Lonestar

My pleasure. Several of my friends have this unit in a variety of vehicles. To a man, they enthusiastically recommend it and a couple have "tested" the warranty. Excellent product with great customer service is the recurring theme.

The only negative I see is the initial cost. But the quality of the unit and service, combined with the ease of installation and ability to transfer it to another vehicle offset that. Who wouldn't want a W-30, clone or not, with a six speed auto with overdrive?

Qwik71442

the Gear Venders will need floor pan clearancing in the tunnel around the adapter but is not a problem with an air hammer being careful. I can post pictures if needed....

Lonestar

I'd like to see some pics....

Bluemeanie

Me Too!!

Qwik71442

here are some pictures...

Qwik71442

more...