Competition Rearend help for the strip...

[Morse]

Hey guys, I need a little advice. I need a rearend for my half ton to race in pro street. With a 33'' tall tire and a 3. 55 gear, it only comes out to about 130 at 4,000 rpm. . Does anyone know where to either get a numerically lower gear for the dana 80, or know where I can pick up a dana 70 with 3. 07 gears? I don't see the need turning the engine much over 4,000. Any opinions or personal experience would be very appreciated. .

 

[MPalachuk]

When I did the math I came up with 3489rpm at 130, 4025rpm at 150.

mph x 168 x 3. 55 =_________ divided by 16[inches] minus 28%[o/d]

tire diam

 

[crawler]

You can get a higher gear (lower numerically). But at 4000 on a 33" tire the truck will go 160 in O. D.



To top out at 130 in O. D. with a 3. 55 rear you would have to run something close to a 27" tire.



Later,

Wes

 

[Morse]

Thanks guys. . I was just using the calculator on thedieselgarage. I currently have the 80 with 3. 55 gears. . Nice to know I don't have to buy more parts. .

 

[Turbo Thom]

I think if you stay close to the stock height with the slick, at 4000 you will be doing allthe engine will do. I mean like 31 inches. I would worry about the 60' times and let the top end take care of itself. At least till I got down to the 1. 5 times 60' times.



. . Preston. .

 

[DHRA]

Brad, call your tire manufacture and find out the growth percentage of the tire at 130 mph, that may be useful... .

 

[Turbo Tim 1]

I'm not sure of the overdrive ratio of the automatic but check out the gear ratio speed calculator in my signature. Looks like you should be around 150mph.

 

[Morse]

Thanks for all the info. . If I need to go to a 31'' tire I will. . I've already purchased 33x15. 50's. At this point, I just don't want to slack on anything. .