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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 84scottsdale454 on May 19, 2011, 10:04:54 pm

Title: 84 2wd 454ci w/ th350....whats gears do i need?
Post by: 84scottsdale454 on May 19, 2011, 10:04:54 pm

im curious on what opinions i can get! i have a very slightly modded 454 in my c10 with a turbo350 trans and im trying to figure out what gears i should use in my rear end! im unsure what they are right now,but i do know that when i hit the interstate my top speed is 65 safely! what combos do yall guys have? should i just sacrafice the extra money for a 700r4 trans??? id like to make it where i can drive on the interstate more to drive it to truck and car shows!

Title: Re: 84 2wd 454ci w/ th350....whats gears do i need?
Post by: rwhit57 on May 19, 2011, 10:24:54 pm

I would be curious to know what kind of rpm's you"re running at 65, you said safely?. A lot of these trucks had the 3:08 gears. That's what mine has. It is not quick at all, but at 70-75mph it is breathing easy. This would probably be an easy rearend to find. 

Title: Re: 84 2wd 454ci w/ th350....whats gears do i need?
Post by: 84scottsdale454 on May 20, 2011, 09:15:57 am

it doesnt have a tach in the truck but im assuming 65 mph because when im on the interstsate the semi trucks even past me! i have 20" boss 338 wheels and my speedo is kinda off! the truck may top out at 100mph so i know the rear gears are low!

Title: Re: 84 2wd 454ci w/ th350....whats gears do i need?
Post by: Grim 82 on May 20, 2011, 11:38:49 am

I would pop the cover and see what's in it now, and then switch it up to the next numerically lower gear set.

Title: Re: 84 2wd 454ci w/ th350....whats gears do i need?
Post by: Edahall on May 20, 2011, 01:02:18 pm

If you don't tow then for best fuel economy, get a 2.73 rear end.

Title: Re: 84 2wd 454ci w/ th350....whats gears do i need?
Post by: zieg85 on May 20, 2011, 01:06:00 pm

My 454 likes low rpms, gets the best mileage 50-55 mph. 

Title: Re: 84 2wd 454ci w/ th350....whats gears do i need?
Post by: 84scottsdale454 on May 20, 2011, 04:02:22 pm

if i had my 454/th350 with 273 gears then what speed or rpm would be comfy on the interstate?? its getting lowered in 3 weeks and will not be towing anything EVER! btw im not worrying about loosing acceleration because i have all the intentions of changing the heads or cam or both!

Title: Re: 84 2wd 454ci w/ th350....whats gears do i need?
Post by: Edahall on May 20, 2011, 05:11:22 pm

Assuming your truck is a 1/2 ton and you're using 235/75/15 tires and assuming you get 50 rpms of slip in the torque converter, here's the rpms at various speeds.  With this setup, you'll pull in good fuel economy numbers at around 55-60 mph and you'll notice a big reduction in sound levels in the cab.

55  1797
60  1956
65  2115
85  2750

Title: Re: 84 2wd 454ci w/ th350....whats gears do i need?
Post by: VileZambonie on May 20, 2011, 05:30:06 pm

Go with the 700R4

Title: Re: 84 2wd 454ci w/ th350....whats gears do i need?
Post by: 84scottsdale454 on May 20, 2011, 06:27:28 pm

I think the cost will be a lot. More if I went with just a trans! I can change my gears and install a cam and prolly have a good result but for a lot less! Right? I have the money and its killing me to make the right choices