I wonder what gear ratio on a 1948 Olds Dynamic 76 with Hydramatic?
I have read somewhere that Hydramatic equipped cars have somewhere around 3.60-3.70. Is this true?

 

From My 1948 Master Chassis Parts Book, page 336:

76 and 98 Hydramatic had 39:10 gear sets which is 3.9:1

The standard transmission 76 had 41:9 gear sets which is 4.55:1

Interestingly, the 1948 78 with hydramatic had two options, 3.9:1 for "hilly" areas and 3.63:1 for standard driving conditions. That might be where your 3.6 to 3.7 guess came from.

The 1948 66 and 68 Hydramatic had the 3.63:1 rear end ratio (40:11)

It's great to see you posting on CO
Jerry Brown

 

Thank's Jerry.
I have the opportunity to buy a nice 48 Dynamic 76 club coupe which is completely stock and rustfree that's why I'm asking. I have the stock rear axle left from my 47 coupe and it sounds interesting to hear that the 66 and 68 series with Hydra had 3.63:1. Do you know if that was the case on the 47 too? Here's a photo of the 48.

 

Seems like I came up with an answer on my own question...
I disassembled my 47 axle and this is what I found




I changed the rear axle on my 47 and mounted a 10 bolt Chevy and luckily I had the original one left. Looks like I'm ready to close the deal on the 48!

 

Good luck and let us know how it turns out. If you get it post more pics.

 

Thank's, I will post more pics.

 

That 48 looks to be in great shape. Good luck

 

Thank's, If everything goes as it should I plan to close the deal on Wednesday

 

Nice rig, hope all goes well with your purchase.