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4-11 gears vs 3-73

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Fishinfool

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I’m thinking about putting 4-11 gears in my rig because I’d like a little bit more low end power the engine in my rig has been built a little bit and it has 35” mud tires on it it gets about ten miles to the gallon I’m just curious what the pros and cons are going to be if I swap From3-73
 
Really won't be many cons.
May even get better mpg because the engine won't have to lug to get around.
 
Also, use a GPS app to figure distance and mileage. The 35s throw the speedo off. My 33s threw my speedo off 14%. I actually get a little over 12 mpg on flat land with a turbo 350.
 
Fishinfool said:
I’m thinking about putting 4-11 gears in my rig because I’d like a little bit more low end power the engine in my rig has been built a little bit and it has 35” mud tires on it it gets about ten miles to the gallon I’m just curious what the pros and cons are going to be if I swap From3-73
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There are many threads here on selecting gear ratio. Search and read. Give us more information and then advice can be more specific. How do you use the vehicle or plan to use it? Which transmission? How has the engine been modified? Are any other modifications planned for the future? Which axles do you have? Are you interested in a traction aid?

EDIT: in your other thread you say it's a '91, so we'll assume it's a 700R-4 and NP241 with electronic speedometer. So yeah, correct the speedometer and that will correct the odometer and then you can calculate mileage correctly. With overdrive I would go to 4.56, which brings the torque up 22%, whereas going 4.10 is only a 10% change. Honestly 4.88 is useable with 35's. Do yourself (and us) a favor and measure how tall the tires really are.
 
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Blue85 said:
There are many threads here on selecting gear ratio. Search and read. Give us more information and then advice can be more specific. How do you use the vehicle or plan to use it? Which transmission? How has the engine been modified? Are any other modifications planned for the future? Which axles do you have? Are you interested in a traction aid?

EDIT: in your other thread you say it's a '91, so we'll assume it's a 700R-4 and NP241 with electronic speedometer. So yeah, correct the speedometer and that will correct the odometer and then you can calculate mileage correctly. With overdrive I would go to 4.56, which brings the torque up 22%, whereas going 4.10 is only a 10% change. Honestly 4.88 is useable with 35's. Do yourself (and us) a favor and measure how tall the tires really are.
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I plan on using it for mostly off roading but obviously there will be some hiway use just not very much the engine has a muther thumper cam edelbrock intake and carb and vortex heads the tranny is a 700 r4 with a monster 2800 torque converter and a shift kit it’s also not a 91 Itsa 90 and the tires are brand new so they are 35”
 
You'd be amazed how much tires differ from manufacturer to manufacturer, I've seen 35s that were 33" tall and I've seen 33s that were almost 34" tall.

Primarily off road, 4.88s all day.
 
Fishinfool said:
I plan on using it for mostly off roading but obviously there will be some hiway use just not very much the engine has a muther thumper cam edelbrock intake and carb and vortex heads the tranny is a 700 r4 with a monster 2800 torque converter and a shift kit it’s also not a 91 Itsa 90 and the tires are brand new so they are 35”
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Technically, you want enough gear to get you above the stall rating of the converter so it’s not slipping all the time (generating additional / unnecessary heat).
 
nvrenuf said:
Technically, you want enough gear to get you above the stall rating of the converter so it’s not slipping all the time (generating additional / unnecessary heat).
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Good thing you brought it up.
When I saw 2800rpm stall, I don't think 4.88 would be good with this.
4.56 would probably be best.
But those who said 3.73 to 4.11 is not worth it, I did exactly that and couldn't be happier.
Stock TBI 350 with 700r4, and it was a dog with 33" tires and speedo was off.
Went with 4.10 axle and it was good acceleration and the speedo was spot on.

My tires were true 33"
Most 35" tires are 33-33.5"
But to the OP if you measure the tires we can give you better advice.
4.56 would be a safe bet regardless
 
700r4 has a lockup converter, so the 2800 stall won't matter at highway speeds
 
As others have mentioned ya really need to have given the actual mods to receive accurate information for best results.

Also anyone running a cam in a SBC with 235/249 duration at .050 in a heavy truck with a 2800 stall should not be concerned with ten MPG.
BTW, that converter is a little much for that grind - you are missing out on a little bit of the power curve for cruising speeds.
Also mentioned earlier get that cruise speed RPM above that stall or you are gonna cook that trans and converter.
 
Not with a lockup.

When your cruising, at speed, in 4th gear there is slip. Meaning no heat build up.
As for acceleration, and driving around town, that part doesn't build enough heat to matter.
Multitudes of 3 speed no lockup hotrods running stall converters drive around town without cooking the trans .
Long distance highway cruising and no lockup, yes, you will cook the trans. Lockup takes that out of the picture here.
 
Missed the lock-up part of the conversation ( oops ) but still the cam is not totally happy with such low of an RPM at cruising speeds.

With these mods let that power curve set the cruise speed and gear options and don’t waste time and effort chasing MPG - or back off to a little more mild grind.
 
Am running sbc 700r4 on 33 (advertised) with 4.88s, next tires will be as close 35 as I can get.
Can cruise 75 @3000 rpm 60-65 is 2k-2.5k. 60+ in 3rd is 3200+ finial ratio in od is 3.42.
If it was a dedicated crawler I would go 5.38 which is 3.76 in od
My cam and stall are smaller.
1600 rpm stall. Thinking of changing to 1800. Cam is summit grind 1102. 204°-214°@.050. .421 &.444 with 112° centerline.
 
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