indian88
I'm about to build a chain drive box running 23.1-26 tires turn 5500 rpm pretty sure I'm going 3:1. What rpm, tire size and gear is everyone running??
Cummins shakes it Cummins brakes it
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5tonjeep
I'm interested in building a chain drive too. just not sure how to go about it. So if you could post some pic's or let me know where to look that would help me get started.
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IRON MAN
I run pretty much those size tires, maybe a little taller and I was running a 1:1 case with 19.5:1 axles .. a powerglide with only 1.8:1 first gear and running around on hard ground was good but when I burried the tires I was seriously undergeared with a 600 cub big block.  The transmission was overheating bad from the lack of gearing and I was having to shut down everytime I gOt it burried and went 100 feet  ... so I wouldnt go that route again .

Your 3:1 with a 6.72:1   2.5 ton rear would be right at 20:1 ... so if you have a th400 I think you will be ok, but if you have a glide you might not do well when its burried.

Right now I have a small block chevy 347 in the same truck with 19.5:1 rear and a 1.96:1 np 205 in low ( like 38:1 overall gear ) and  I can pull 1500 lbs behind the truck straight up a 60 degree angle hill almost idling .. its almost as if you have to be able to change gears at least 1.5:1 whenever you really need to sometimes .... 

Im fixing to try a th400 with 19.5:1 rear with a 1.3:1 case (25.5:1 overall ) with a small block that will turn 7000 ... hopeing it will do more than just idle around ...
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indian88
I was going chain drive but found a case I'm going to try for the price can't beat it. 16" drop 3.75:1 with 2wd option lol. Switching back to a 4l80e so with the meritors I'll be at 1st gear 57:1. 2nd I'll be 34:1. 3rd will be 23:1. Od will be 17:1. The case is a little lower geared than I was wanting but it will put my gears closer together and with od I'll still have the final gear I need
Cummins shakes it Cummins brakes it
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Shaun (yota)
indian88 wrote:
I was going chain drive but found a case I'm going to try for the price can't beat it. 16" drop 3.75:1 with 2wd option lol. Switching back to a 4l80e so with the meritors I'll be at 1st gear 57:1. 2nd I'll be 34:1. 3rd will be 23:1. Od will be 17:1. The case is a little lower geared than I was wanting but it will put my gears closer together and with od I'll still have the final gear I need


What kind of case did you find?
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Damage1
Here is a great gear ratio wheel speed calculator.http://www.grimmjeeper.com/gears.html
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