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73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Topic started by: C-Moore502 on January 15, 2011, 01:48:26 pm

Title: lowering gear ratio
Post by: C-Moore502 on January 15, 2011, 01:48:26 pm
So I have a 84 K20 with the 6.2 and my truck has the 3.73 gear ratio. I think I would like to lower it to 4.10. I'm still a little new to 4x4's so any input would be greatly appreciated. If I do change the gearing which parts besides the axles and transfer case would need to be re-geared as well?
Title: Re: lowering gear ratio
Post by: Da67goatman on January 15, 2011, 02:20:51 pm
I think you should be fine unless your running some 35" or larger tires.
Title: Re: lowering gear ratio
Post by: C-Moore502 on January 16, 2011, 09:52:17 am
Well I was considering getting some 35's and a 6" lift kit but I'm still trying to figure it all out.
Title: Re: lowering gear ratio
Post by: motion427 on January 16, 2011, 12:52:45 pm
Just need to regear the differentials,not the transfer case.
Title: Re: lowering gear ratio
Post by: Irish_Alley on January 16, 2011, 04:15:28 pm
I think you will be good with 3.73. I'm running 4.10 with a sm465 and 38s. So it has a 1.1 transmission ratio and at 50 she's at 2k. That's high in my opinion I would like to step up once I get a chance
Title: Re: lowering gear ratio
Post by: C-Moore502 on January 16, 2011, 06:01:40 pm
Alrighty then, well thanks for saving me some time and money then guys
Title: Re: lowering gear ratio
Post by: dcayers on March 19, 2011, 11:56:28 pm
You can expect to lose some fuel mileage until you put the bigger tires on it. We just pull the 4.10's out of the 84 6.2 and put 3.42 in and helped the fuel mileage tremendously. Diesel's like lower rpm range.
Title: Re: lowering gear ratio
Post by: 1979C20 on March 20, 2011, 06:10:48 am
I think you will be good with 3.73. I'm running 4.10 with a sm465 and 38s. So it has a 1.1 transmission ratio and at 50 she's at 2k. That's high in my opinion I would like to step up once I get a chance
irish, my trucks got the sm465, 4.10's or 4.11's and 30" tires and it runs 2k rpms at 45! 50 is closer to 2200rpms.
Title: Re: lowering gear ratio
Post by: Irish_Alley on March 20, 2011, 10:53:24 am
Lol thought I had it bad

I made a little boo boo ment 55 was 50 with the 4.56
Title: Re: lowering gear ratio
Post by: 4x4x4x on March 21, 2011, 03:28:01 pm
So I have a 84 K20 with the 6.2 and my truck has the 3.73 gear ratio. I think I would like to lower it to 4.10. I'm still a little new to 4x4's so any input would be greatly appreciated. If I do change the gearing which parts besides the axles and transfer case would need to be re-geared as well?
we have a 1985 k10 with a 6.5 turbo diesel and 700r4. it had 373's, when we replaced the tires with 33/1250r15 goodyear mtr's the gearing was too high, it was hard to pull hills (shifting between 3rd and 4th gear) and the truck lacked power. we switched out the front and rear differential gears (and added electric lockers) and now the truck runs great. i checked the speedo with a gps and it reflects the correct speed, and the engine rpm is back in the stock range. the last time i checked mpg is was 22mpg hwy (driving easy)

randy's ring & pinion site has rpm calculators that will allow you to compair engine rpm/tire size/differential gear ratio.

http://www.ringpinion.com/Calc_RPM.aspx
alec

Title: Re: lowering gear ratio
Post by: bake74 on March 22, 2011, 11:08:20 pm
So I have a 84 K20 with the 6.2 and my truck has the 3.73 gear ratio. I think I would like to lower it to 4.10. I'm still a little new to 4x4's so any input would be greatly appreciated. If I do change the gearing which parts besides the axles and transfer case would need to be re-geared as well?
we have a 1985 k10 with a 6.5 turbo diesel and 700r4. it had 373's, when we replaced the tires with 33/1250r15 goodyear mtr's the gearing was too high, it was hard to pull hills (shifting between 3rd and 4th gear) and the truck lacked power. we switched out the front and rear differential gears (and added electric lockers) and now the truck runs great. i checked the speedo with a gps and it reflects the correct speed, and the engine rpm is back in the stock range. the last time i checked mpg is was 22mpg hwy (driving easy)

randy's ring & pinion site has rpm calculators that will allow you to compair engine rpm/tire size/differential gear ratio.

http://www.ringpinion.com/Calc_RPM.aspx
alec



      Which gears did you switch too ?  4.11 s.
Title: Re: lowering gear ratio
Post by: 4x4x4x on April 14, 2011, 06:56:26 pm
So I have a 84 K20 with the 6.2 and my truck has the 3.73 gear ratio. I think I would like to lower it to 4.10. I'm still a little new to 4x4's so any input would be greatly appreciated. If I do change the gearing which parts besides the axles and transfer case would need to be re-geared as well?


      Which gears did you switch too ?  4.11 s.

we went with 411's, also added auburn gear ected limited slip/electic lockers and rear disk brakes. just had marine injectors installed, big difference in power.


Title: Re: lowering gear ratio
Post by: beastie_3 on April 14, 2011, 07:34:04 pm
im running 33 tires and 3.73 gears and I dont have a problem with it.
Title: Re: lowering gear ratio
Post by: 1979C20 on April 14, 2011, 07:50:31 pm
My mom has 3.73s and 35's on her 03 avalanche andbits doin a bit of a number on her engine
Title: Re: lowering gear ratio
Post by: beastie_3 on April 14, 2011, 07:54:23 pm
key word: 2003

Our trucks can handle more than a newer IFS truck
Title: Re: lowering gear ratio
Post by: 1979C20 on April 14, 2011, 11:24:10 pm
Well, im talking more the rearend than the ifs. The truck has only been switched into 4 wheel drive once since we got it in like 06. Im just saying the high gearing with the tall tires has taken a toll on the engine. It burns through like a quart and a half of oil in a little over a month and its at like 65k miles?.