Dana 60 gear ratio selection question

[usraptor]

My 1970  Cuda has a factory 4-speed and OEM stock Dana 60 and 4:10 gear set.  The 4:10s are not conducive to freeway driving to attend car shows, cruises, etc.  I would like to change to possibly a Dr. Diff.  3:54 gear set.  On his web site he offers two 3:54 gear sets, a Motive Gear and OEM Spicer.  Forgive my ignorance but what is the difference?  FYI, my engine is a 440 with a 512 stroker kit, roller hydraulic cam, aluminum heads and intake, headers and 3" exhaust.  I'm probably pushing 500 HP plus.   I can't even begin to keep the rear end planted in 1st gear or even 2nd for the most part and even get rubber during a hard shift to 3rd.  At 55 MPH I'm running 3K RPM with the 4:10s.  I would like to drive at a comfortable RPM at 65 MPH on the freeway.   I owned a new 1970 Cuda that had the 383 Magnum, 335 HP engine, 4-speed and 8 3/4 with a 3:55 sure grip and I didn't have any problem running it on the freeway.  However, I realize my current set up is a whole different beast so I don't know if the 3:54s would allow comfortable freeway driving or not or should I go with the Dr. Diff 3.23 gears?   I don't intend on racing the car at the drag strip so I'm not really concerned with low ETs.  I may do an occasional burn out or a hard run through the gears, but I would like the car to be more user friendly at cruising speed.  (Did people really drive these at constant freeway speeds with these 4:10s back in the day?)  Has anybody else changed their 4:10s to either 3:54s or 3:23s or have a factory Dana 60 with the 3:54s or 3:23s and what was/is your experience/recommendations.

[RUNCHARGER]

How tall are the rear tires? Generally 3.23's are a lot nicer on the freeway than 3.54's are.
3.54 will drop your RPMs about 12% at a given speed so that might not be enough to get you where you want. A 340 would be a different deal but 440's have pretty good grunt on the low end.
I took the factory 4.10 out of my Hemi Cuda after the first 50 miles. I installed a 3.54 and it was still humming pretty good at 60MPH, it would have been much nicer with 3.23s on the highway.

[Chryco Psycho]

Times have changed , yes we drove the highways with 4.10s at higher RPM but engine barely lasted 100k miles
Now we are so used to overdrives & with the 512 the torque is immense , so RPM is not as nessisary .
3.54 is a better choice for you , as Run said 3.23 would be fine also but I had no luck in finding a source for a set of 3.23 for a Dana , they did make them at one point but no one has them now so to go to 3.23 you need the 8 3/4 diff or you need to swap to some sort of OD trans , Passon has the Hemi 4 spd with OD , or the 855 with 5th gear OD or you can use the 23 spline 833OD from the dodge trucks , I have done numerous conversions like this or you could swap in a tremec which would be the last option I would choose . Any of these you could retain the 4.10 gear ratio as it would drop the RPM to approx .71%or = to 2.91 rear gear ratio

[usraptor]

Chryco, Dr. Diff makes a 3:23 for the Dana 60.

[Chryco Psycho]

That is great !

[Brads70]

Too bad we didn't live closer  I took out 3:54 out of my DrDiff brand new Dana and went to 4:10 . Shipping them would be a deal killer.

[Spikedog08]

Chryco, Dr. Diff makes a 3:23 for the Dana 60.

Seriously?   OMG . . I need one of those and someone to set it up!      

[RUNCHARGER]

Ha, ha: I've laid underneath these cars setting up those gears enough times to not want to do it again. On a 60 anyway. I think I've done about 10 or 12 of them in total.

[Brads70]

Chryco, Dr. Diff makes a 3:23 for the Dana 60.

That must be fairly new as it was not an option when I bought my Dana from Cass. 

[Chryco Psycho]

Sorry Dave I am not coming to set up your 3.23 gears in the Dana .
I looked everywhere for a set of 3.23 for Dana none anywhere , obviously this is a new supply

[Marty]

Chryco, Dr. Diff makes a 3:23 for the Dana 60.

Saved.

Thanks for the lead. Just what I was looking for.

[cordodge]

Too bad we didn't live closer  I took out 3:54 out of my DrDiff brand new Dana and went to 4:10 . Shipping them would be a deal killer.

lol Brad, Im going the other way. going to get the 3.23s and remove the 4.10s my dr diff 60 came with, although 3.54s maybe ok as well, im running 28" tires. Motor makes a ton of torque, add the 4.10s and its ok but believe id be happier with something higher.

[Brads70]

Too bad we didn't live closer  I took out 3:54 out of my DrDiff brand new Dana and went to 4:10 . Shipping them would be a deal killer.

lol Brad, Im going the other way. going to get the 3.23s and remove the 4.10s my dr diff 60 came with, although 3.54s maybe ok as well, im running 28" tires. Motor makes a ton of torque, add the 4.10s and its ok but believe id be happier with something higher.

I can dig the out if your interested but if your going to the trouble of changing them might as well be sure and get the ratio you want.

[cordodge]

Too bad we didn't live closer  I took out 3:54 out of my DrDiff brand new Dana and went to 4:10 . Shipping them would be a deal killer.

lol Brad, Im going the other way. going to get the 3.23s and remove the 4.10s my dr diff 60 came with, although 3.54s maybe ok as well, im running 28" tires. Motor makes a ton of torque, add the 4.10s and its ok but believe id be happier with something higher.

I can dig the out if your interested but if your going to the trouble of changing them might as well be sure and get the ratio you want.

Thanks Brad, your probably right
Maybe I'll do the gear ratio calculator thing to see how it goes. I've done lots of 8-3/4s but never a Dana so I'll need to find someone close to do it so I dont screw it up lol

[Spikedog08]

I have already been checking to see who can set it up, found a shop about 45 minutes from me that will do it . . . pretty sure they did my last one.  Charges $300 with the rear out and $450 if it is still in the car.  I will pull it and take it to them.  I removed a 4.10 years ago and thought I put in a 3.55 but discovered it was a 3.73 which is not what I was told I was buying.      

I have been considering an overdrive addition or even a new trans . . . but hate to part with my 18 spline that I bought.  This should make me happy!  YES!      

Will be awesome to cruise the highway at a comfortable RPM and keep up with traffic!  Traffic average speed here is about 85 . . .