[62131]

As I posted the other day that I was going to take the 32 out for a good long drive today.  I have a stock 350 motor with a TH350c transmission and a rear end with 2:41 gears, Fuel mileage was not so good something needs to change. Any suggestions?   

[TFoch]

My 33 has a stock 350 with a 700R4 and a GM 10 bolt with 3:43 gears.  Very happy with the way it drives and the gas mileage.
I'm running a 255 70 15 rear tire.

[Rattiac]

What diameter tire are you running ?

Cherokee's come with 3:55's (Chrysler 8.25 axle)
If it'll fit width wise.
Gear changes are so expensive that I found a axle with the ratio I wanted.

[62131]

its really tall, don't remember but will check

[62131]

What diameter tire are you running ?

Cherokee's come with 3:55's (Chrysler 8.25 axle)
If it'll fit width wise.
Gear changes are so expensive that I found a axle with the ratio I wanted.

p255 R70 15  about 28.5" tall

[TFoch]

What diameter tire are you running ?

Cherokee's come with 3:55's (Chrysler 8.25 axle)
If it'll fit width wise.
Gear changes are so expensive that I found a axle with the ratio I wanted.

p255 R70 15  about 28.5" tall

That's the same tire I'm running.

[sammons]

I would guess you are way too high geared, especialy with a tall tire to boot. My old '66 Impala wagon I got from my grand folks had a 350/ with orig 2spd power glide. When the speed limit was dropped from 70 to 55 back in the 70s  the gas milage went out the window. If I ran it in low at 55  it came back up. Had an '85 Chevy 4x4 350 with the overdrive and in overdrive at 75 and under, milage sucked (13-14mpg) Pull it out of OD and milage came up (17-18). They were just bogging down running at lower rpm's. I don't recall the rear ratios on either but they were high, but not as high as yours.

[62131]

Without measuring he rear end width and knowing what it came out of it's 58" wide by what I found on the web, 

[TFoch]

I got mine from a 2WD Chevy S10.  Width from wheel mounting surface to the other is 54.5"  The 4WD S10's are 59".

[sammons]

I don't know how much difference the weight/cubic inch makes. My '57 weighed right at 3400 with me in it. 283 (.060 over) and a Quadrajet, M-22 4spd 27" tall tire and 3:36 rear gear. That was my best gas mileage combo. 21-22mpg @ 73mph. I tried 3:08, bogged, and 3:55 good pick up but wound up too much. Wish there was some kind of formula there.

[62131]

I got mine from a 2WD Chevy S10.  Width from wheel mounting surface to the other is 54.5"  The 4WD S10's are 59".

looking online at our local junk yard they have a  7-5/8 ring gear units with 3.08 and a 3.73 ratio I think I would rather have a 8-1/2 ring gear

[Rattiac]

Here's something to help you out rpm--wise.
I calculated mine to what rpms it would run at 65.
http://spicerparts.com/calculators/engine-rpm-calculator

Im running a th350, 29.5" tires and 3.73 gear.
About 27-2800 rpms at 65.
Mpg was 20 if I light pedal it.

[madmike3435]

As I posted the other day that I was going to take the 32 out for a good long drive today.  I have a stock 350 motor with a TH350c transmission and a rear end with 2:41 gears, Fuel mileage was not so good something needs to change. Any suggestions?

wow, 2;41 rear gears,  maybe if your running at Bonneville all out.  You need 3.36 gears for low , mid range performance with 28--29 tall tires.. Or even 3.08.  The problem is the 350 TH you need the lower 3;00---3;08 right down ..  you don't will the motor at 3000 rpm with 3.42 or 3.55 gears but car will perform

best set up is the 700R4 over drive at .70 4th gear 2200 rpm.    You want to buzz motor drop into 3rd gear at 60 and see 3000 rpm all day long

My 35 std coupe has 700R4 and great, phaeton has a 350TH, with 3.54 jag gears, BUUUUUUUUUUUUUUUUUZZZZZZ.

going to run 6 speed tremec in roadster.


mike.....

[EDNY]

Tom is correct with the S10 info, if you want drum brakes use the rear axle out of a 95-97 S10 Blazer they are 59" WMS to WMS (wheel mounting surface),  The 2WD S10 has a 54.5" WMS and commonly found with 7-1/2" ring gear BUT the 2WD Xtreme can be found with the 54.5" with 8.5" ring gear.  (I have one in my 33 Chevy)

What GM did was put a full size truck 3rd member between the S10 axle tubes. They are rare...like I said have one in my 33 Chevy and (2) stashed away. You'll see the 8.5 in some ZR2 packages also...but they are really wide.

[EDNY]

Here's a blog where the guy replaced his S10 7.5 rear axle with an 8.5", you can see the difference in the cover, the 8.5 is almost round.


http://donosti71.blogspot.com/2010/02/rear-axle-updte.html