I took a trip today to meet the gentleman that will be restoring my truck and I told him my plans, ideas, upgrades, etc. I told him about the stroked 400 engine, the ZF swap, and other ideas like replacing the speedometer so I can see it go 100 mph and then he asked me what gears I had and I told him I believe they are 4.10.

I also told him I plan on running 34x11.5 maybe 35x12.5 tires and he was suggesting like a 3.73 gear. I'd like to keep the lower gears but I also want to be able to run the 80mph speed limit here in Idaho.

Thoughts?

 

My mostly original '78 with 31" tires and 4.10 runs 70-75 fine. With 34" would do 80 OK with more power. I think 4.10's will work though spinning just a little fast for a stroker. If you want to run 80 all day maybe 3.73 would be better. If you want to run 80 "as needed" 4.10's would be fine. Also if towing, 4.10's preferred.

 

Here is what some folks think.

 

35s with a 4.10 is decent with a four-speed. ..even better with overdrive of ZF. Leave it be IMO.

 

I've seen that chart before, it's just been awhile. I think I may keep the stock gearing after seeing the chart. Any other thoughts? Real world applications?

 

35" tires? Go with the 4.10, no question.