The Stovebolt Site Forums The Shop Area General Truck Talk too tall gears?

i have a 10bolt axle here i was going to use for my 49 rear end the gears work out 3.23 now with a 200hp motor 5 speed o.d manual and 235x75x15 tyres would this be any good? i was thinking i may need it lower?
main uses are daily driving but need it to get up and go if i stomp on it climb hills with ease minimal highway driving cruise at an easy 60-70 would be nice

also how/where do i check to see if its a 8.2 etc?
incase i need another gear set

What transmission is it? If your lower gear ratios are pretty high I think it would work, but your rpm would be real low in overdrive. For get up and go you would just have to downshift appropriatley. My $0.02 Others with more smarts should be along. Good luck.
Jeff

It also helps to know what the engine is. Your setup shows about 1900 rpm at 60 mph. If the engine is set up for torque, you should be okay. But expect to downshift in the hills.

You didn't mention your type of transmission or 5th gear OD ratio....if it's a T5 with a .72 OD it will be marginal, if it's a .86 it will be a little better. I tried running a 3.08 w/.72, 235, with 29" tall tire. Worked great as a 4 speed....now run a 3.42 and I can lug down to 50-55 in OD. The optimum rpm range for the 235 with a torque (stock) cam is between 1700 and 2400. You didn't mention what 200 hp engine, so your torque curve could vary appreciably. Run you numbers on:

http://csgnetwork.com/multirpmcalc.html

The bottom calculator is a bit more specific.
Hope this helps.

Dave

Shouldn't be lugging in OD, anyway. Direct is for power. OD is for idling on flat ground. The numbers sound okay to me, Limey, but I hate a screamer. If you can cruise at 1500 - 2000 that's okay, and downshift for power. The tranny'll live longer.

i also posted this on the hi po

engine is german gm 3.0 24valve twin cam injection straight 6 gearbox is a getrag manual 5 speed around .72 o.d 5th

204hp at 6000rpm 200lb torque at 3600 rpm


weight of truck is about same as donor vehicle so i guess if i do the math and gear it the same it should be pretty good. without checking i think tyres on donor are 195x65x15 axle ratio 3.7 it would top out at 140 mph + and 0-60 was pretty good

24V twin cam? Sounds like a short-stroke engine. Do you know bore & stroke? How about peak torque speed? That is your most economical cruising speed, and where you want to spend your overdrive time.

For years all the U.S. auto builders used the Borg Warner OD unit. It was a 30% OD and the standard rear gear used by ford, chevy, studebaker etc. was a 4.11. This gives a 2.88 in OD which is an ideal highway gear. In underdrive the 4.11 will let even a short stroke, low torque, high winder pull good. Ones fuel mileage with these old units depended entirely on the driving habits of the operator. The govenor would let the OD engage at just under 30 mph and if used like this even big V8's would get respectible mileage. With that said a 3.23 might be a little shallow but give it a try.

well its no less torque than the standard motor and has double the hp all be it at higher revs
it even looks like the old unit and its gm

from what i worked out with 235 75 15 tyres i would need around 4.11-4.30 to match the donor cars 3.7 on 195 65 15 gearing allthough i dont wish to go 140 mph! so i guess a little lower would be fine and have it accelerating pretty well. the donor car will give 30 + mpg and have read reports of 40+ with a few easy mods

the donor car is also heavier than a standard 3100 and the ,new, engine /gearbox is a lot lighter than the old 3100 unit so allthough i never chose this to build some ,race, car it should hopefully be a good allround daily driver
just need to get the gearing right