8 3/4 or Dana

[Cranky]

Perhaps the 3.91 gears were thinner and weaker than numerically lower ratios, or the pinion gear was just too small? At any rate, Chrysler knew of the weakness. This 1968 Field Bulletin says that the 8 3/4 3.91 was barely strong enough for even the 383 4-speed combo.

View attachment 550496

The 8 3/4 only has one size carrier so the pinions can get pretty small as the ratios go up so a 3.91 ring gear would be thicker than a 3.55 etc. Don't recall seeing or hearing of problems behind 383's. Maybe they got a weak batch of gears for a short run....?

 

[Mike67]

Already had the trans, rear was stock

I guess I misinterpreted your earlier post, it sounded like you were going to have the trans "mildly built"...
If your future could include a 700+hp motor I wouldnt waste your time or money on anything other than a dana or a modified 9". 2nd'ly even if you are just looking to get by until then I dont think you would ever get any of your money back on a 8. As most that would look for something ro hold that kind of hp are going to go with what has been mentioned here already.
Good luck with it!

 

[YellowDodge67]

I guess I misinterpreted your earlier post, it sounded like you were going to have the trans "mildly built"...
If your future could include a 700+hp motor I wouldnt waste your time or money on anything other than a dana or a modified 9". 2nd'ly even if you are just looking to get by until then I dont think you would ever get any of your money back on a 8. As most that would look for something ro hold that kind of hp are going to go with what has been mentioned here already.
Good luck with it!

Thanks. Yeah I got a good deal on a 489 case 3.23 sg to get it driving again. But a 9in or Dana is in my future. I've had the car for 12 years so it's changed directions a few times and I've acquired parts along the way, hence the RV 440 and the mildly built 727.

 

[tomlin]

My worst was in a 1980 Monte Carlo. GM 7.5 axle. Mild 350 with a aggressive TH350 transmission. Broke the cross pin on the first to second shift spinning the right rear tire. Blew the pin and spider gears through the differential cover. Then the fun began. The C-clips fell out, lost one axle (wheel drum and all went flying) The other side came out far enough for the center to hit the road. Ground to a stop. Axles missed the body panels. One junkyard assembly later and it was round two. LOL.

 

[5.7 hemi]

Don’t use a ferd 9 inch in your Mopar, get a Dana.

 

[YellowDodge67]

Don’t use a ferd 9 inch in your Mopar, get a Dana.

I could flip a coin on that one lol. Will probably end up with a GM trans anyway so remaining pure Mopar is unlikely.

*prepares to be banned*

 

[5.7 hemi]

If ya got a race car, understandable, but for a hot street car, no reason at all to run ferd or chebby parts on your Mopar.

 

[YellowDodge67]

If ya got a race car, understandable, but for a hot street car, no reason at all to run ferd or chebby parts on your Mopar.

Not a true racecar but to have a TH400 built for what I need it to do is less expensive and more readily available than a 727. I work in the car business so I can be a brand bigot like the best of them but since money isn't unlimited, I can sleep at night as long as it's Mopar powered.

 

[Photon440]

If ya got a race car, understandable, but for a hot street car, no reason at all to run ferd or chebby parts on your Mopar.

Sometimes the parts that you want, like an OD automatic, won't fit without cutting the car. Unless you use a different brand. Not everyone can afford the Mopar tax on stuff that is mostly hidden anyway.

Lots of stuff gets mixed up in the corporate world. Dana isn't a Chrysler brand, while 80's GM trucks with the 'MY9' transmission code were using the Chrysler O.D. 833. Ram trucks use a Chevy (AAM) rear now, no more Dana after 2002. It's mostly the engines that I like to see stay true to the brand.

 

[5.7 hemi]

I’m giving ya guys chit, not my car, so do what you like, can afford, think is best. I’ll still like ya in the morning. Lol!

 

[YellowDodge67]

Sometimes the parts that you want, like an OD automatic, won't fit without cutting the car. Unless you use a different brand. Not everyone can afford the Mopar tax on stuff that is mostly hidden anyway.

Lots of stuff gets mixed up in the corporate world. Dana isn't a Chrysler brand, while 80's GM trucks with the 'MY9' transmission code were using the Chrysler O.D. 833. Ram trucks use a Chevy (AAM) rear now, no more Dana after 2002. It's mostly the engines that I like to see stay true to the brand.

^this

 

[YellowDodge67]

I’m giving ya guys chit, not my car, so do what you like, can afford, think is best. I’ll still like ya in the morning. Lol!

I'd do the same thing lol. I have 2 Fords too and I gave my diehard Ford friend a mountain of grief when he put a TH400 in his turbo Mustang. Still do in fact lol

 

[rumblefish360]

Perhaps the 3.91 gears were thinner and weaker than numerically lower ratios, or the pinion gear was just too small? At any rate, Chrysler knew of the weakness. This 1968 Field Bulletin says that the 8 3/4 3.91 was barely strong enough for even the 383 4-speed combo.

View attachment 550496

There level and what it actually handles are two different things.
Now it is a shame that they didn’t upgrade the 383 to a DANA level!

 

[Photon440]

Now it is a shame that they didn’t upgrade the 383 to a DANA level!

But if you read that bulletin, that's exactly what they did in those cases. Warrantee claims with the 3.91 were upgraded to a 4.10 Dana.

 

[rumblefish360]

But if you read that bulletin, that's exactly what they did in those cases. Warrantee claims with the 3.91 were upgraded to a 4.10 Dana.

But I did read that!
Allow me to rephrase what I said;

It is a danm shame the 383 wasn’t made more powerful so Chrysler Corp would put in the DANA. This way there would be more DANA rears that came stock behind a more powerful 383.

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