Automatic and rear-end ratio

[Bakins]

My left knee continue to get worse. For that and a few other reasons, I'm thinking I may change my plans and just use an automatic in the '57. Not 100% decided, just weighing my options. I'm still planning on using an LS3. If I go automatic, I'm thinking a 4l85E. It may be overkill, but the 60/65/75 seem to get labeled as "weak" and I'd rather overkill it to start with.

The gear ratios on a 4l85e are: 1st 2.482, 2nd 1.482, 3rd 1.000, 4th 0.750. I've got a 3.45 rear-end (Dana 44). I'm thinking I'd want to swap out the rear-gears to something like a 3.75 or a 4.11 if I decide to swap. I'll be running tires about 27" in diameter on the rear.

Thoughts?

Also, I've been doing reading about making a clutch "easier" for folks like me.

I actually have some time to work on the car. I'm so behind, but stuff happens....

[56-210Sedan]

Bruce/Tunned 55 used the 4.11s in his dana 44 rear and had good thing to say about that choice.

[chevynut]

Bruce is using a T56 manual (with a .5 6th gear), so that's a different story. The 4.10 Viper gears is what I plan to use in my Nomad too, with my T-56.

Personally I think the 3.45 gears would be near-perfect for an automatic with the 2.48 first gear and .75 4th gear. Automatics with the torque converter seem to work well with higher gearing than a manual tranny. In any case, I'd go ahead and try them and decide later if you want to change. You can drop the pumpkin out easily and change the gears, without even dropping the batwing if you don't want to.

The 3.45 gears will have your engine turning at 2415 RPM or slightly higher (depending on rolling radius) so personally I wouldn't go with any lower gearing. I'd prefer to have lower highway RPM.

[chevynut]

Besides, you have more important stuff to work on right now. ;)

[markm]

I run a 1957 Olds 9.3 rear end with 3.42 gears and a 700R4 in my 56 and it appears to be about perfect.

[Rick_L]

What's perfect to one might be no so good for others. The 3.45 seems a good middle of the road choice. Higher numeric for more performance, lower numeric for more mileage/quietness. I think the combo could run fine on anything from a 2.9 to a 4.1

[c57heaven]

wonder why the overdrive is .75 A 700r4 is .70 and a 200r is .67?

[Bakins]

Besides, you have more important stuff to work on right now. ;)

Well, with work/family commitments, I mostly only have time to think and dream about the '57. I think that gets me into more trouble than actually working on the car as I keep coming up with more and more ideas... After the holidays, I should have weekends freed up finally.

[Bakins]

Personally I think the 3.45 gears would be near-perfect for an automatic with the 2.48 first gear and .75 4th gear. Automatics with the torque converter seem to work well with higher gearing than a manual tranny. In any case, I'd go ahead and try them and decide later if you want to change.

Thanks for the advice. Seems like a good way to go.