what gears to use
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what gears to use
here is my problem. i have a 73 f250 4x4 with a well built 390. im running 35x12.50 tires, and i have 3.56 gears in it now. i have sitting in the shed a set of 4.10's for both front and rear. i dont know if i should switch gears, i drive about 90% in town. i sometimes take it on the interstate at 70mph. right now she is taching 3k at 70. in town i know the 3.56 gears dont help the stop and go driving. i do pull with this truck, i have yanked many tree stumps and a few suvs with this. so do i run my 4.10 or stay with 3.56. i really would like to see an increase in mpg, as im getting 5 in town right now. im thinking the 3.56 gears are hurting me by making the motor do all the work.
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Joined: Apr 2008
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From: Big Sky Country
I'd go with the 4.10's, IMO 35's w/4.10's are the best all around tire/gear combo for these trucks (highboys), going from 3.56's to 4.10's will lower your highway rpm's by 250-300 and help your mpg's around town and be even more of a stump puller than before.
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I think thats a typo, 4.11's will raise cruising rpm, and my guess would be by about 500 or so rpms. If you drive in town that much and are pulling with it, the 4.11's will work alot better. But if you ever start driving it on the freeway youll hate em. Mine is my DD so i drive it all over all the time, and not much city driving, running 33's and 3.55's with overdrive, i cruise 60 at about 2k rpms. and with the 5 spd i have more than enough gearing down low. Im planning on keeping the 3.55's when i bump up to 35's, unless i go to 38's then i will go to 3.73's or 4.11's
Post Fiend
Joined: Apr 2008
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From: Big Sky Country
Yea you're right, i got that backwards, the OP's tach must be off, running 3.56 gears w/35's @70 mph would put him around 2,400 rpm's, not 3,000 rpm's as stated, so 4.10's would raise his highway rpm's to around 2,700 but help over all since he does 90% in town driving.
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nope tags are still on the truck saying 3.56 gears. never thought the tach might be off but it seems about right by listening to the motor. now you have me thinking here....having driven her for 2 years i dont think its got lower gears than 3.56. it doesnt pull like it has 4.10's in her already. huh
Lead Driver
Joined: Jun 2006
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From: Near Yosemite CA
nope tags are still on the truck saying 3.56 gears. never thought the tach might be off but it seems about right by listening to the motor. now you have me thinking here....having driven her for 2 years i dont think its got lower gears than 3.56. it doesnt pull like it has 4.10's in her already. huh
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Post Fiend
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From: Big Sky Country
X2, something is amiss here, either your tach is off or the gears were swapped out.
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yeah im wondering if my tach is that far off...well i guess i wasnt thinking about this but my spedo isnt 100% either, having the 35's on it. the spedo read 60-65 and the tach was at 3k. so i suppose i may have been going faster than 70. im guestimating here that it was 70 at 60 on the spedo. i really do not think i have lower gears than 3.56
Posting Guru
Joined: Nov 2006
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From: Riverview, FL
Well if you do find out you have 4.10's in there already, let me know.... I have 3.50 in mine and running 35's with a 300, I need more gear bad. I might buy those 4.10's if you don't need them! That is if you would sell them.
Lead Driver
Joined: Jun 2006
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From: Near Yosemite CA
yeah im wondering if my tach is that far off...well i guess i wasnt thinking about this but my spedo isnt 100% either, having the 35's on it. the spedo read 60-65 and the tach was at 3k. so i suppose i may have been going faster than 70. im guestimating here that it was 70 at 60 on the spedo. i really do not think i have lower gears than 3.56
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