Rusty Bowtie
General Category => General Discussion - Intros => Topic started by: 62131 on April 09, 2017, 05:19:15 PM
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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?
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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.
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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.
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its really tall, don't remember but will check
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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
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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.
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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.
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Without measuring he rear end width and knowing what it came out of it's 58" wide by what I found on the web,
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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".
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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. ;)
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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
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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.
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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..... 8)
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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.
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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
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I have located two different rear ends 3.08 and a 3.73 which would give the best performance?
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the 3.08 will give you excellent cruising, gas mileage due to lower RPM , but will not much in the way of off the line performance but that too depends on camshaft, intake, tire height. Bigger the tires height wise, more it cuts the gears.
Also depends on powerglide, TH 350, or a 700-R4.
3.73 will tend to buzz the rpm's to 3000 at 70 mph with NO overdrive.
If you know the rear gears in your late model ride with 700R4, slip it into 3rd gear at 1---1 and see what the tack is telling you.
My 2003 S10 v6 with 4.3 and 3.42 gears, 700R4, 60 MPH drop it into 3rd and get 2800-3000 rpm, shift into overdrive at .70 and voila..........2200 rpm
mike 8)
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I got 373 gears in the roadsrter and at 70 iit's about 2200 rpm in 5th gear. but in 1st gear it's awhole lot of fun.
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With staying with the S10 4x4 95 thru 97 rear ends available in the 59" wms to wms there's just a few ratios to choose from, it seems the3.08 is the most common. I did find two 3.73's today. Having a stock 350 and th350c with plans on using the lock up convertor while at highway speeds and the 28" tall tires, I'm thinking the 3.73 is the gear to use.
What's your opinion?
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Well...I'm stuck with 3.08s right now. Have TH350 w/o lock up, 26" tire, I'm betting my 301 ain't going to be a power house off the start. If I had it going I could give more info. I'll prob build my 350 for lower end power and call it good. :(
My '69 Vette had 3:73 gears (350/4spd/25" tire) and pulled hard, loved it. Gas mileage wasn't great but not bad at 17mpg @65. I found a 3:55 gear and liked it better, gas mileage came up to 20, just not as quick.
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I'd probably go with the 3.73's. I would rather have something a bit deeper than a taller gear than be disappointed with a lack of power on take off.
A buddy I cruise with , will swap another pair of wheels w/taller tires on long distance trips.
He has a 50 Chevy with a 4.3ltr th350, 3.73 rear.
One day we're gonna race as soon as I get rid of the wood inside.
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If it were me I'd go with the 3:73's. I don't spend much time on the highway at 75 mph. I spend more time accelerating from stop lights and cruising the back roads. The 3:73'swould fit my driving style better than the 3:08's. Just my humble opinion.
Tom
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With staying with the S10 4x4 95 thru 97 rear ends available in the 59" wms to wms there's just a few ratios to choose from, it seems the3.08 is the most common. I did find two 3.73's today. Having a stock 350 and th350c with plans on using the lock up convertor while at highway speeds and the 28" tall tires, I'm thinking the 3.73 is the gear to use.
What's your opinion?
The Blazer has the 59" WMS unit - the S10 truck has either the 54.5" or 63" (ZR2). The 95-97 Blazer axle has drum brakes for sure...but some later units might have drums...but most are disc after 97. Important to note is that if you have factory width leafs springs...the calipers on the disc units won't mount because they contact the leaf springs. I found out the hard way and had to install a drum axle. If you have a 4 link...you can mount either.
I'm sure you know to look in the glove compartment for the RPO codes for gear ratio and posi unit identification.
http://www.sierragear.com/gm-rpo-axle-ratio-identification-codes-3/
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I see there's a 3.42 out there this might be the gear to find and use??
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I see there's a 3.42 out there this might be the gear to find and use??
That's what I have in mine. Very happy with it.
Tom
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its the stock rear gear in my 2003 chevy S-10 extreme.
235 x 65 x 16 tires. At 60 mph in 3rd gear 2800--3000 rpm, slip it ( 700R4 ) into overdrive at .70 and rpm drops to 2200
mike 8)
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I found a 3.42 today out of a 98 blazer 4x4 with drum brakes, one more junk yard to check hoping to find a 3.42 with g80 option found several 3.73's with g80 option today getting closer. I'm not looking for a tire burner more of a cruiser.
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Well now I'm really undecided on what gear to use. Please help me with a decision ???
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My dilemma is the 3:42 gears and Th 350 transmission......was offered a 700r4 for cheap...guess i'm going that route..gotta change out transmission mount and length of drive shaft.... what your opinion?? ...
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Well I'm being told the 3.42 gear is the perfect gear for the the TH350 and the 3.73 will work fine to just will turn couple hundred rpm,s higher on highway speeds. I have already had my transmission rebuilt along with a new drive shaft made. I would like to know how much difference in fuel mileage would it really make between the two