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Gearing for 35s with 700r4

A

AzTrailHunter

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I know this is discussed a lot and i'm split between 4.10 to 4.56 gears I use it as a daily driver but take it on trails on weekends I have a new 406 SBC that Push's the truck up small inclines in overdrive at 50 with 3.08 gears just fine but I want more power than I have and believe I can get better gas mileage too I think with the power I have 3.73s might work good for that but I'm looking for input.
 
4.56 for sure. Honestly 4.88 wouldn't be terrible. 4.10 is too close to your current ratio and you will probably wish you'd gone deeper later on. You might consider the 4.10 with a TH350, but with OD....gear it!
 
I would go 4.88 no questions about it.

I love my 4.56 combo with 33s.
 
Thanks guys 4.56 sounds good now I'm interested in 4.88 I cruise at about 70 twice a week and occasionally 80 on i-40 but mostly city driving at 50 I'm shooting for 10 mpg, right now I get about 5-6 mpg with my 3.08 gears
 
At 80 mph im at 3k rpms with a 2500 rpm stall converter in my 700.

70 is 2500 rpms.

Carbed 408 sbc, I got 9.5 on one of my trips to the dunes (before playing).

I was pretty happy with that personally for what it is. I like that the transmission doesn't have to work while cruising, and you can tell.
 
You're lugging bad, that's why your milage sucks. 4.56s put the truck back to stock ratios w/ 35s. I turn about 2100 rpm at 70 in my '89 w/ a 700, 4.56s and 35s. Holds OD on all hills and is plenty low for froading. I get 11.5 mpg no matter how or where I drive it, always have, even before the tires/ gears.
 
Back when I daily drove my 92 it had 4.56 gears, 35's, 700r4, cam, intake, chipped TBI 350. Great setup for all around driving, consistant 11-12 mpg for more offroad performance I had always wished I went with 4.88 gears but I rarely drove the highway.
 
I have 4:56 in my '70 with a 700R4, and it was more fun when it had the 33's on it. Now with the 35's , it isn't bad , just i can tell the difference. With the smaller tires, I could get 11 around town with the A/C on. I don't know what it does now. It has a SMI built Q-jet on the 462 roller fat block.
 
4.88:1. I am running 4.56:1 with your tire and trans combo. Goes into D on any little up hill. Would also like to have the greaing for wheeling.
 
Take it out of OD and take a drive. See how much you mileage increases. If you're holding 50 for extended periods of time it can give you a taste of how lower gears will feel. (At least on the highway)

Edit....what cam is in the 406? Knowing what the cruising rpm the motor is set up for will make your gear choice easier.
 
ChrisPerry said:
Take it out of OD and take a drive. See how much you mileage increases. If you're holding 50 for extended periods of time it can give you a taste of how lower gears will feel. (At least on the highway)

Edit....what cam is in the 406? Knowing what the cruising rpm the motor is set up for will make your gear choice easier.
Click to expand...
This is good advice. With your current 3.08 gears driving around without overdrive will be pretty close to 4.56 gears with the OD. If you don't like running around now without OD then you really won't like 4.88 gears. While I tend to recommend lower gears I will say that daily driving and the fact you have enough engine to push the truck up hills with 3.08's you may not want real low gearing. 4.10's are also a pretty drastic change from 3.08. On the other hand if might go to larger tires down the road then do lower gears now.

About fuel mileage, make sure the odometer is accurate. If you change gears or tire sizes without recalibrating the speedo/odo then it will throw off the MPG calculation. If you install lower axle gears without fixing the odo it will automatically look like the MPG is better, even if it really hasn't changed. The opposite is true if you install larger tires...the MPG will automatically looks worse if you don't change the odo.
 
Basic Operating RPM Range: 1,800-6,000

Duration at 050 inch Lift: 226 int./234 exh.

Advertised Duration: 270 int./278 exh.

Valve Lift with Factory Rocker Arm Ratio: 0.480 int./0.498 exh.

Lobe Separation (degrees): 111

Recommended stall 2200rpm

................................................................................
Okay, that cam should have a cruise rpm around 2900-3400, and doesn't look like it starts to make good power until 1800-2200(based on the above specs and recommendations)

I would think best cruise mileage would be 23-2500 and 32-3300 for good power while cruising

I ran some numbers for you.....

these figures are for 35" tires in overdrive

GEARS ............ RPM@70.......... @50
3.08 ..................1449..................1035
...............................................................
4.11 .....................1933..................1381
...............................................................
4.56 ................... 2145...................1532
...............................................................
4.88 ................... 2296..................1640
...............................................................
5.13......................2413...................1724


I would think 4.88's unless larger tires are in your future. If they are go 5.13's
 
basicly you cant go to deep with overdrivetrans .

few guys here have 5.13 and 700r4 with 35" tires and love it .

http://www.grimmjeeper.com/gears.html play with this site for gear / rpm/mph info .

also bigger tires over stock should also be 1 step over whats needed to get back to stock so you don't hit the bottom of the power band but hit in the mid range so you don't lug a lot .

and 700r4 if to high = highway gear = hunt in/out over drive a lot and fry trans .
 
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