742 case with 3.91 gear - Manufacturer Recommendations

[OKDart]

I went from 3.23 to 3.91 in a car with a mild 440 and 29" tall tires and it made it quite a bit more fun. But I think 3.73 would be a better compromise. I ordered one from Dr. Diff last year, I think to my door was $1600ish. The repro cases are all 489's, yoke choices were 7290 or 1350, and it came with a helical gear "sure-trac 2". They make a conversion U-joint if you have a 7260 yoke.
Mopar 8 3/4" (8.75) 489 Case Third Member

 

[1 Wild R/T]

Back in the 80's I drove a 440-6 Challenger with 4.10 gears from central Ca to San Diego... And back.... 3.91's for a mostly city car are fine... And fun.. I've got 4:30's in this.... And I drive it a lot...

 

[Heat-Med]

Back in the 80's I drove a 440-6 Challenger with 4.10 gears from central Ca to San Diego... And back.... 3.91's for a mostly city car are fine... And fun.. I've got 4:30's in this.... And I drive it a lot...

View attachment 1618503

Lots of 4.30s available around me. I am just concerned it will be too much.

 

[1 Wild R/T]

Lots of 4.30s available around me. I am just concerned it will be too much.

Take your car for a drive and leave it in second gear... That's the equal to 4.68's

 

[Bee1971]

Been running 3:91 Gears in my 383 BEE for over 30 years now - Auto Trans

28” 275 60 15” Tires help a little

Fun yes - Really helped the torque curve of the stock 383 down low - Different camshaft , intake blah blah

Now that I am running a 383/432 Stroker Kit as of five years ago - Edelbrock heads , nothing to crazy , Street car

The Torque with the new engine down low is just incredible around town , then add those same 3:91 Gears

5600 - 5800 RPMs comes on so fast , to fast , smoke the tires at will

My 71 Superbee is a factory 489 case 3:23 Sure Grip

Thinking of now heading back in that direction with mentioned above

So it really depends on your engine torque curve , cruising , RPMs , and what you want to do

I don’t NEED 3:91 gears anymore

An overdrive would really BEE the cats *** , but not going to happen

 

[Dave6T4]

I bought a new 1969 SuperBee, 383, automatic, that came with factory 3.91's. I drove it everywhere, and never worried about the rev's; 3000 rpm. @ 60 mph. Gasoline was about $0.35 / gallon back then. The extra gearing made my car surprise a lot of guys on the street. I remember meeting a couple of 442 guys at a burger joint one day, who wanted to street race. They were sure they could mow me down. Didn't happen!
When I first put my '67 440 R/T together, I put 3.91's in it, remembering the fun I had years before with my SuperBee, with same gearing. What a disaster! The extra low end torque of the 440 made my car kinda treacherous, especially if there was my moisture on the highway. It would burn the tires at will. They stayed in there about a month before I swapped them for 3.23's. A good compromise gear would be 3.55's. I ran them in my "one-of-none" '67 R/T wagon, with 440, 4-speed. They were fun in it.

 

[Krooser]

Talk to Moser Engineering in Indiana...they have been great on everything they have done for me.

Quality parts....fast shipping and unequaled service. Shortened my 9.25 axles on a 3 day turnaround... unheard of.

moserengineering.com

 

[Heat-Med]

Talk to Moser Engineering in Indiana...they have been great on everything they have done for me.

Quality parts....fast shipping and unequaled service. Shortened my 9.25 axles on a 3 day turnaround... unheard of.

moserengineering.com

I will consider it, but was hoping to find an OEM.

 

[Krooser]

I will consider it, but was hoping to find an OEM.

Ship them a used pumpkin and they will build what you want and have it back to you in five days.

 

[Chi Town Runner]

Heat-Med

Check your PM messages

Frank

 

[Pool Fixer]

I got a new one made for me by Quick Performance. 489 case with eaton tru track, 3.23 gears. 1600 including shipping. It's crappy here so i havent had the car out to test on the highway yet.