Highway gear options/advice? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Kell · 06-22-2016, 10:00 AM

250 inline 6 with standard 3 OTT. My truck cruises comfortably at 55, anything above that is pushing it in terms of long term reliability I'm afraid. I would like to be able to drive on the highway instead of fearing it, I drive my truck a lot and this would allow me to drive it a whole lot more. I came up with 3 basic options?

1. I have 235/75/15 on there now, I would like to switch to taller tires anyway, but not sure if that will be a noticeable change? Any advice, or pics of taller tires (mine just look too small).

2. Switch the rear end out with an automatic? I've heard the rears are geared a little higher in an auto, this should bump it up some, but possibly make 1rst a little high?

3. Switch the transmission out, this is a pain, and finding a 3 speed with OD would be next to impossible around here. 4 speed floor shift loses some of the old school vibe I like about the truck, but I guess is an option. Have heard certain V6 S10 transmissions will hold up?

Any thoughts? Thanks

benbloom · 06-22-2016, 10:07 AM

i think ultimately your going to be happiest with an OD trans, with that said changing the rear can make a world of difference on the highway and if you go with something high like a 3.08 you wont need overdrive at all. of course your sacrificing some low end power there, so its all a tradeoff.

Mike C · 06-22-2016, 10:15 AM

One nice thing about the 6 cylinder is that the 4.3 V6 T5 is a great transmission to swap in and they aren't real expensive compared to the harder to find more expensive V8 transmission. That would be my first choice for better all-around drive ability.

The other choice is to your point, taller tires. Or switching to lower numeric gears (you should have 3.73 so 3.07 would lower rpm 20%) but these also all reduce the low speed gear reproduction.

More difficult is the T5 swap, but more value to be had as well IMO.

barry1982 · 06-22-2016, 10:13 AM

Hi There,

If I was doing it, think I would try find a Diff from a 67-72 that had a 350/Auto. Pretty sure those had a little higher gear ratio than your 250/3 speed. In the late 70's early eighties GM offered a 3 speed standard with overdrive. I believe it was called an "A833" . They are rare..... (I have a couple). Both of mine came in 1982 GMC 1/2 tons with the 6.2 liter Diesel. These transmissions can be bolted to a Chevy V-8 or 6 cyl. They came factory with a "Hurst" type floor shifter.

06-22-2016, 10:00 AM	#1
Kell Registered User Join Date: Nov 2015 Location: Paducah, KY Posts: 37	Highway gear options/advice? 250 inline 6 with standard 3 OTT. My truck cruises comfortably at 55, anything above that is pushing it in terms of long term reliability I'm afraid. I would like to be able to drive on the highway instead of fearing it, I drive my truck a lot and this would allow me to drive it a whole lot more. I came up with 3 basic options? 1. I have 235/75/15 on there now, I would like to switch to taller tires anyway, but not sure if that will be a noticeable change? Any advice, or pics of taller tires (mine just look too small). 2. Switch the rear end out with an automatic? I've heard the rears are geared a little higher in an auto, this should bump it up some, but possibly make 1rst a little high? 3. Switch the transmission out, this is a pain, and finding a 3 speed with OD would be next to impossible around here. 4 speed floor shift loses some of the old school vibe I like about the truck, but I guess is an option. Have heard certain V6 S10 transmissions will hold up? Any thoughts? Thanks __________________ 1970 C10 Longbed, 250 Inline 6, 3 OTT

06-22-2016, 10:07 AM	#2
benbloom Registered User Join Date: Mar 2015 Location: san rafael california Posts: 202	Re: Highway gear options/advice? i think ultimately your going to be happiest with an OD trans, with that said changing the rear can make a world of difference on the highway and if you go with something high like a 3.08 you wont need overdrive at all. of course your sacrificing some low end power there, so its all a tradeoff.

06-22-2016, 10:15 AM	#3
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,727	Re: Highway gear options/advice? One nice thing about the 6 cylinder is that the 4.3 V6 T5 is a great transmission to swap in and they aren't real expensive compared to the harder to find more expensive V8 transmission. That would be my first choice for better all-around drive ability. The other choice is to your point, taller tires. Or switching to lower numeric gears (you should have 3.73 so 3.07 would lower rpm 20%) but these also all reduce the low speed gear reproduction. More difficult is the T5 swap, but more value to be had as well IMO. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

06-22-2016, 10:13 AM	#4
barry1982 Registered User Join Date: Oct 2015 Location: Waskatenau, Alberta Posts: 259	Re: Highway gear options/advice? Hi There, If I was doing it, think I would try find a Diff from a 67-72 that had a 350/Auto. Pretty sure those had a little higher gear ratio than your 250/3 speed. In the late 70's early eighties GM offered a 3 speed standard with overdrive. I believe it was called an "A833" . They are rare..... (I have a couple). Both of mine came in 1982 GMC 1/2 tons with the 6.2 liter Diesel. These transmissions can be bolted to a Chevy V-8 or 6 cyl. They came factory with a "Hurst" type floor shifter.



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