I recently bought a parts truck and it came with 2 D70 rears. I checked the numbers on each,one is a 3.73 and the other 4.10. The 4.10 is off the truck and the 3.73 is good. I dont know about the 4.10 Has anyone ever swapped in a 3.73 for a 3.54 with a CTD? Would I even notice anything?

 

I rarely tow more than 5000lbs with lots of highway miles above 70mph.
If I could have gotten 3.54 gears in my 2005 I would have seriousely considered it

 

It will make a difference in rpms for sure. It'll feel like you don't have near the load on to make it go, but you'll run into top speed faster and usually won't get as good of mileage empty. You might get better towing though.

 

I didn't think you could get 3.73 gears in a Dana 70.

 

Its from a 1978 d300 gasser, ring and pinion all check out. I really need a 4.10, but im not 100% sure that its ok. The 3.73 is good, no noise, etc I will replace bearings to be sure though. I really need some extra grunt, I usually gross 26k or better

 

I wanted 3.73's for my truck when I swapped. My option was 4.10. The
3.55's with the 315's just was not geared right for towing 16k everyday. The 4.10's are great, but they are a little to low empty. 3.73's would have been a great compromise.