Got the 58 Apache close to road ready. Running a 350 and a 2004r, B&M kit to shift off of pressure. Looks like I have a 2:73 rearend from a 73 firebird, if I remember orrectly. What would be a range of acceptable gears to replace the 2:73s? Will be running 235 or 255/15s. I'm thinking 3:42 or maybe a 3:73 ( TA or Z/28?). What would be good cars for a swap-I could do an entire rear end by myself, have never done a ring and pinion. Thanks.
Just gonna take a big ole WAG here.Maybe some where in the neighbor hood of 3.55`s,or a bit lower. Good luck.Have fun.Be safe. Leo
You'd be happy with 3.70'ish rear end ratio, given your tire and transmission combo...........have a 200R4 behind 383 stroker in my 65 Impala wagon with stock 3:36 rear gear, run 245/15's on back, and this combo doesn't like O/D until at least 60 mph........will change ratio to 3:70's soon..........
3.70:1 or higher numbers for serious hauling but just for street running around empty and the odd small chores 3.54:1 is very suitable
A 3.90 rear ratio would give you roughly a 2.93 od ratio. The 200r4 has a 0.67 od. Keep in mind that the 200r4 burns about 70 hp just to operate it vs 35 hp for a Turbo 350
transmission don't "burn hp" "just to operate". They take a percentage. otherwise, cars wouldn't creep in drive, at idle, would they?
Well excuse me for not using the "Proper Terminology", but I think everyone gets the picture that HP is robbed through the whole drive train operation at different power applications with the automatic trans component's being the biggest drain.
Leave the gears as-is. But change the cam to a short duration retro-hydraulic roller [200 deg duration] and put a small carb on it ,so it purrs like a kitten With 25-1/2" diameter tyres it will cruise at 1600rpm at 65mph [similar to a modern car] and get decent mpg's. You'll be able to use your pickup as a long distance cruiser without pounding your eardrums. Around town the low end torque and lower 3 gears come into play.
There are lots of ways to skin this cat. 3.42 to 3.73 gears would work well. You could also try it with the gears you have in it now, you may like it just fine, Or not, hard to say.
Don't you mean the newer the better. A set of 1999 manufactured gears [18 years] is made of a lot higher density "metallurgy" than 1947 gears [70 years]
Knowing a little about my pals, maybe I should have made the statement "fill in the blank"...................
Suggest you just run what you have, then determine what you might want. My kids car (OT) has a 2.77 rear, stock 350 with a 700R4, weighs a solid 3800lbs as I recall...no issue in town, or on the highway. Now if we put in a bigger cam, stall converter, higher breathing intake and induction, we might re-think what's in there...but she just cruises it....but then again, why are her rear tires wearing out faster than the fronts? And she pulls early 20's MPG on freeway driving.
i think it depends on what you want to do with the truck. big cam, pulling loads or hot rodding around town? i would go lower gears. stock motor ,flat terrain and long trips leave those gears and see how "bad" they are.
It's just going to be a driver. Stock cam, aluminum intake, Q-Jet, headers. I have driven it around, feels pretty gutless at take-off. And I don't want it lugging in OD at 65-75.
With the 273 gear you’ll run about 1600 rpm in overdrive at 70 mph With the gear ratios in that 200r4 it shouldn’t lug anywhere
What's the tyre diameter? If you're got 25-1/2" Tyres , try a 3.36 ratio and at 65mph it'll be cruising at 2000 rpm [75mph= 2300rpm] The 200R4 has a lower 1st than a T350 A 3.36 ratio with a 200R4 is the same in 1st as a T350 with a 3.65 ratio in 1st.
At highway speed (60-65mph) you want your rpm to be between 1800rpm and 2100rpm. My 35 Chebby with 3.54:1 and 235:75 tyres is 1,879rpm at 65mph. My OT DD with 3.73:1 and 235:75s is 2,121rpm. 2.73:1 is IMHO too high for an OD transmission, engine will labour in OD. At 65mph a 200R with 235:75 tyres, engine speed is:- 1,387rpm with 2.73:1; 1,707rpm with 3.36:1; 1,799rpm with 3.54:1; and 1,895rpm with 3.73:1. So many options and as Jim stated, there are many ways to skin a cat.
Check out Wallace racing rear gear calculator. Your stall speed and type [lockup or non] may come into play .I would think that 3.73's would be close.
My 51 convertible is running a crate 350 with 373s in a 10 bolt Nova rear. It is quick enough from the traffic lights and cruises 65 to 70 nicely. If it's a cruiser you want, the 373s were always the gears that I've seen recommended. I'm even using the same gear in the rear of my 52 Hard Top with a 235 and T-5 combo.
Thanks for the hard numbers and real world info guys. This is what Im looking for. And a 78-81 Z28 rear end .
Most of the last of the rear wheel drive Chevy police cars had 235/70r15 tires with a 700 overdrive and ran 3.42 gears. Not all ,but most some had 2.73 some had 3.08.
3.55-3.73s should work out pretty well from the info and intentions you've mentioned. Nothin' worse than having a pig that can't get out of it's own way on the low end. Still should cruise decently at highway speeds w/ the OD trans and a set of fairly tall tires.
One thing to keep in mind is that the late model cars that ran these OD transmissions and gears on the taller side is that they were fuel injected and had computer controls. If you're running a carb, you'd have to be about 1800-1900 rpm on the low side or your car will be pretty unresponsive/bogging at freeway speeds and your fuel mileage will suffer. Obviously lighter cars can tolerate taller gears in this situation...but right about 1900-2100 highway cruising rpm is pretty ideal I think..
The Jalopy Journal
