3.23, 3.55, or 3.73

[Cranky]

Actually ran my best ET with a 2.94 rear end vs a 3.91 with a mild 383 probably because of traction off the line with the 3.91's but man, the 2.94 was sweet on the highway!

 

[lemondana]

Define your "Highway Use", the two lane highways around here-the speed limit is 65, the Interstate is 75 with most running 80. If you run 3.23's on the Interstate for an extended period, you WILL be wishing for 2.94's or better yet 2.76, or best of all, an OD trans.

 

[Curiousyellow71]

Rather then going old school with low gears I'd suggest installing a 9 1/2 dynamic torque convertor or Ptc and 3.23. You will get a car that launches hard like 3.73 or lower but drives like it has a modest convertor. 383 will wake up w a convertor. The 9 1/2 is tight enough that its still moves the car down highway speeds good but flashes the torque like its got 4.56s, best of both IMHO.

 

[OKDart]

Now if you asked in the 80's, people would be telling you to go 4.10 or 4.56. I guess we've gotten used to slower engines on the highway.

I think the main difference is 55 MPH speed limit vs 70+ of today. I think the turnpikes around here just went to 80 MPH in certain areas.

I plan on going with 3.73 with 28" tires. I took a road trip through the southwest 20 years ago when the speed limit was 65 MPH in a car with that setup, and it was a good compromise.

 

[Photon440]

I don't think I remember anyone actually doing 55.

 

[HawkRod]

With the 14" tire, I'd say the 3.55 is a good compromise.

As others have said, it depends a lot on what type of driving you will be doing. All highway, then 3.23's or even a 2.94. All local streets, then 3.73 or 3.91. I have 3.55 gears in both my cars and feel they are a great overall compromise. Good around town, and not too bad on the highway. If you will do some mixed driving without an overdrive, then I think 3.55 are the best.

On a 14 maybe 225/70 or 245/60

I agree with some about getting rid of the 14" rims. Tires for 14" rims are quite limited. I haven't checked, but it might be impossible to find a 245/60 tire for a 14" rim. Check first before you make any final decisions.

 

[Don Frelier]

I think you can get 245/60s but they really need a 7" or wider rim.

 

[BAFRAID]

Thank you. I appreciate all of the advice provided. Driving the different types would make this choice a lot easier. I looked at Dr. Diff and I can build new pretty much anything I want for about $1000 with a 489 case. Three other questions I have are,
With the differential choice is a 6 helical sure-trac ll needed/beneficial for a street car?

What is the benefit of green bearings/are they better than stock?

 

[Longknife]

http://wallaceracing.com/calc-gear-tire-rpm-mph.php

 

[kiwigtx]

Now if you asked in the 80's, people would be telling you to go 4.10 or 4.56. I guess we've gotten used to slower engines on the highway.

...reminds me that a PO of my GTX ran 4:56's in it for a year or two. Must have screamed down the highway with those gears.

 

[Demonic]

What is the benefit of green bearings/are they better than stock?

Opinions vary on that issue, but a tapered roller bearing, like the stock ones, have more surface area. More support for the axle. For a street car, I'd stay w the stock setup.

 

[66Satellite47]

The green/ball bearings are good for straight line driving, the tapered/Timken bearings for all around multi purpose use.

 

[AR67GTX]

If you run a loose torque converter, around town and medium speeds it will sound like you are running one gear ratio lower than you actually are. I put a slightly looser than stock Hughes torque converter in my GTX with a 3.55 gears and TF and I would not want to run anything steeper than that except strictly for the drag strip. With a 383 & stock TQ you should be fine with a 3.55 or 3.23. I believe the 3.55 is a great gear for a 383.

 

[BAFRAID]

If you run a loose torque converter, around town and medium speeds it will sound like you are running one gear ratio lower than you actually are. I put a slightly looser than stock Hughes torque converter in my GTX with a 3.55 gears and TF and I would not want to run anything steeper than that except strictly for the drag strip. With a 383 & stock TQ you should be fine with a 3.55 or 3.23. I believe the 3.55 is a great gear for a 383.

Thank you, I am running a stock torque converter. I had it rebuilt at the same time that I had the transmission rebuilt. All to stock specifications.

 

[66Satellite47]

Thank you, I am running a stock torque converter. I had it rebuilt at the same time that I had the transmission rebuilt. All to stock specifications.

A quality aftermarket converter can make all the difference in the car performance. The money spent on a converter like a 9 1/2" or 10" Lupo Dynamic will transform the car. A stock converter is blah.

 

[BAFRAID]

A quality aftermarket converter can make all the difference in the car performance. The money spent on a converter like a 9 1/2" or 10" Lupo Dynamic will transform the car. A stock converter is blah.

You mentioned a couple different sizes and a brand name. Is it as simple as ordering that or are there specific applications to a 383 727 set up?

 

[Johnpat]

3.55s

 

[AR67GTX]

You said a mild build on the engine - if stock magnum cam or close to it, you are probably OK with the stock converter - especially with 3.55 gears.

My GTX is full power and factory air (heavy) and it needed a bit of help getting off the line, especially as it had a tight 12" converter out of something or other - maybe the same Imperial the radiator came out of. I would probably have been fine with a stock (for a 440 Magnum) converter and my 3.55 gears - or a slightly looser converter and 3.23 gears. The Hughes converter is a 2000 rpm stall one but it reminds me of a used 68 Hemi Charger I looked at back in the early 70s. Lot of revs and noise at light throttle but really wakes up with full throttle.

 

[66Satellite47]

You mentioned a couple different sizes and a brand name. Is it as simple as ordering that or are there specific applications to a 383 727 set up?

No, a good converter manufacturer will want a lot of specifics of your combination and use. A "tight" 10" from a good builder will be amazing on the street even with a mild motor. It will also be good with a 3,23 or 3.55 gear. Changing to a 15" rear tire in the 27" plus range would be good too.

 

[33 IMP]

You mentioned a couple different sizes and a brand name. Is it as simple as ordering that or are there specific applications to a 383 727 set up?

Any good converter shop will ask you a ton of questions (fill out a questionair or answer in person) about your combination, the way you drive ,where you drive most, and what you expect to change, or what you want out of your car. I would call several different shops to see what kind of answers you get. Converter choice can be just as critical as cam choice! ATI , PTC, Dynamic, Hughes, Dice, FTI, several other good ones. Local to you is helpful. I would not consider TCI. Its not for nothing that people say that their initials stand for "total crap inside".