The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1960 - 1966 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 01-22-2014, 02:17 AM   #1
62_C20builder
Registered User
 
62_C20builder's Avatar
 
Join Date: Sep 2013
Location: Clovis, Ca.
Posts: 22
Transmission Question

I have a '62 C-20 Chevy truck with a straight 6 and it has a 4 speed transmission. First gear is pretty much useless, but I want to keep the manual transmission. Any ideas how I can resolve the issue? Is it possible to change the gears in the transmission or the rear end? Lost here guys...please throw me a bone. Thanks!
Attached Images
 
62_C20builder is offline   Reply With Quote
Old 01-22-2014, 02:33 AM   #2
Captainfab
60-66 Nut

 
Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,252
Re: Transmission Question

That's the way the SM420 transmission is designed. First gear is not typically used for normal driving. It is meant to be used when pulling heavy loads or slow offroad driving. That said, to achieve what it sounds you are wanting, you will have to either change the differential gears, the complete differential or change to an OD trans. There are a few options for each and there are many threads on each of them. You will just need to decide which way appeals to you more.

The Eaton HO52 differential that is under your truck has does not have any new gears available and replacement parts such as bearings and seals can get expensive. Your differential likely has either 4.11 or 4.57 gears. If it were my truck, depending on the condition of the differential, I would consider changing to either a Dana 60 or a GM corporate 14 bolt. As for an OD trans there is the 3 speed with OD, the T5, and MY6/A833. There is also the NV3500 and NV4500, but those will not bolt up to your 235 engine.
__________________
Power Steering Box Adapter Plates For Sale HERE
Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE
Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE
Hydroboost Mounting Plates HERE
Captainfab is offline   Reply With Quote
Old 01-22-2014, 03:13 AM   #3
jtrichard
Registered User
 
Join Date: Jun 2013
Location: joshua tree ca.
Posts: 1,484
Re: Transmission Question

you just drive it 2nd 3rd 4th dont use first .... the later 4 speed of the same design was L 1 2 3 so people did not try to start out in "first/low"
jtrichard is offline   Reply With Quote
Old 01-22-2014, 08:47 AM   #4
luvbowties
Registered User
 
luvbowties's Avatar
 
Join Date: Feb 2009
Location: southeasternfoothillsofusa
Posts: 1,557
Thumbs up Re: Transmission Question

Possibly the simplest & quickest 'help' for your scenario would be taller tires. Doing the math & assuming a present differential gear of 4.11, if you moved from 28" tires to 32" tires, it would effectively change the final ratio 'seen' by the engine to a 3.60 (4.11 X 28/32 = 3.596; rounded = 3.60).
HTH,
Sam
luvbowties is offline   Reply With Quote
Old 01-22-2014, 01:20 PM   #5
62_C20builder
Registered User
 
62_C20builder's Avatar
 
Join Date: Sep 2013
Location: Clovis, Ca.
Posts: 22
Re: Transmission Question

Thanks guys, I will look at all of these options. You guys rock!
62_C20builder is offline   Reply With Quote
Old 01-22-2014, 03:57 PM   #6
par4tom
Registered User
 
Join Date: Nov 2012
Location: Kingsburg CA
Posts: 581
Re: Transmission Question

I did an NP 440 / MY6 transmission swap. Had the SM420 like you.

The new tranny is a dream with 4th gear in overdrive. First three gears are similar to a Turbo 350 tranny. You can find some information on this in some of the threads already posted here.

You should be able to find one with some effort and only be out about $400 to $600 bucks. Watch for the bellhousing bolt pattern too.

Tom
__________________
My Build Thread
http://67-72chevytrucks.com/vboard/s...d.php?t=705185
How to Get Audiophile Sound in 60-66 Trucks
http://67-72chevytrucks.com/vboard/s...=1#post7236896
Building Your Own Speaker Kick Pods
http://http://67-72chevytrucks.com/vboard/showthread.php?t=730495
par4tom is offline   Reply With Quote
Old 01-22-2014, 04:08 PM   #7
mr andrerson
Registered User
 
Join Date: Mar 2010
Location: riverside ca
Posts: 152
Re: Transmission Question

I swapped mine out for the t-5 behind my 230 in front of the 411 rear and i couldnt be happier. the whole swap is laid out nicely here.
mr andrerson is offline   Reply With Quote
Old 01-22-2014, 04:40 PM   #8
Old Bleu
Registered User
 
Old Bleu's Avatar
 
Join Date: Jul 2013
Location: Loganville, GA
Posts: 115
Re: Transmission Question

+1 for the T5 behind the 230 in my '64.
Old Bleu is offline   Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 12:03 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com