Author Topic: transmission swap or rebuild  (Read 1967 times)

Offline WhtWlf80120

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transmission swap or rebuild
« on: November 03, 2013, 06:56:59 PM »
Got a 81 C20, with an 350 5.7 M engine. Have a standard "H" with granny gear, would like a 5 speed or a possible chance to rebuild the one I have to get more speed. I understand that this transmission setup was the most for that era. But would like to go a little faster than 55mph.

Thanks for all the info in advance.

Offline Jason S

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Re: transmission swap or rebuild
« Reply #1 on: November 03, 2013, 08:52:19 PM »
The NV4500 5-speed manual transmission from '88-up Chevrolet/GMC trucks is a 'common' manual transmission swap. With the NV4500, you get a fairly low gear plus an overdrive gear. 

Take a look on the forum using the search box for other write ups on transmission swaps; including: 700-R4/4L60E & 4L80E 4-speed autos & 5-speed NV3500 LD manual and NV4500 HD manuals and NV5600 6-speed manual transmissions (and others).

Additionally, you may consider swapping rear axle gears (or complete rear end) for something with a higher ratio.  Really, it all depends upon how you normally use your truck. Example:  If you have 4.56 gears and are normally driving highway, then you may want to go to 3.73 or 3.42 gear ratio and keep your 4-speed.
1973 GMC K2500, Super Custom, Camper Special, 350, TH350, NP203, 4.10's
1974 Chevrolet K10, Custom Deluxe, 350, SM465, NP203, 3.73's

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Offline WhtWlf80120

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Re: transmission swap or rebuild
« Reply #2 on: November 04, 2013, 02:18:38 PM »
Thanks for the info.

Offline Engineer

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Re: transmission swap or rebuild
« Reply #3 on: November 05, 2013, 07:25:43 AM »
+1 on the NVG4500.

The gear swap Jason mentioned would be much cheaper.
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2001 Chevy 2500HD 4x4 6.0/4L85E EC/SB
1997 Chevy Blazer 4x4
1994 Chevy K-2500 4x4 C6P 5.7/4L80E
1979 Chevy K-30 4x4 4sp 4.10
1977 Chevy K-30 4x4 4sp 4.10 454

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Offline Irish_Alley

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Re: transmission swap or rebuild
« Reply #4 on: November 06, 2013, 01:47:50 AM »
or bigger tires. but i have 38's and the sm465 trans you have. even with 4.10 ratio you still would be pushing 2800 rpms at 55 im only pushing 2k at 55. so bigger tires or changing the rear. first thing i would do is verify what ratio you have
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Offline WhtWlf80120

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Re: transmission swap or rebuild
« Reply #5 on: March 30, 2014, 06:57:10 PM »
Thank you for all the reply's. Guess I'll keep it this way for now. $$$ tight. Till I get the other list problems taken care of.