Speedometer Gear Reduction Box

[Shaun1162]

So I'm planning on swapping the rearend gears in my C30, and want to know what to do about the speedometer...

Currently the truck has 5.14's, but I'm planning on going to 4.10's.

Can I find a different gear-reduction box that fits on my SM456, or a different gear that goes on the inside of the transmission?

Any help is appreciated, thanks!

[48richard]

Changing the gears in the transmission is pretty simple. You may be lucky and just be able to change the gear that the speedo cable connects to, otherwise you have to remove the tailshaft housing from the transmission and change the gear in there, but I did the whole job in about an hour and a half.

http://www.transmissioncenter.net/sp...n_______va.htm

has all the information you will need about what gears to buy, and if you're lucky (I was) your local Chevy dealer will have them in stock.

[LockDoc]

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The guys and gals with speedometer problems from swapping transmissions and rear ends have another choice also...As explained in this thread.

http://67-72chevytrucks.com/vboard/s...d.php?t=421745

LockDoc

[Fldawg]

Changing the gear where the speedometer cable goes will only change it about 2 to 3 mph, changing the gear in the tailshaft will get you closer. Mine was so far off i used a
speedometer adapter that you find on big truck applicationsgot it dead on with that

[Shaun1162]

Originally Posted by 48richard

Changing the gears in the transmission is pretty simple. You may be lucky and just be able to change the gear that the speedo cable connects to, otherwise you have to remove the tailshaft housing from the transmission and change the gear in there, but I did the whole job in about an hour and a half.

http://www.transmissioncenter.net/sp...n_______va.htm

has all the information you will need about what gears to buy, and if you're lucky (I was) your local Chevy dealer will have them in stock.

I'll definately have to look into that... Hopefully they have the metal gears for the SM465

Originally Posted by LockDoc

-
The guys and gals with speedometer problems from swapping transmissions and rear ends have another choice also...As explained in this thread.

http://67-72chevytrucks.com/vboard/s...d.php?t=421745

LockDoc

Very cool idea, however I've got a factory tach, and kind of like things to be stock, but still what a great idea!

Originally Posted by Fldawg

Changing the gear where the speedometer cable goes will only change it about 2 to 3 mph, changing the gear in the tailshaft will get you closer. Mine was so far off i used a
speedometer adapter that you find on big truck applicationsgot it dead on with that

That kind of how mine is right now... It's got one of those box adapters that comes off of the transmission. Hoping I can just find one of those with the right gears..

[geezer#99]

Here's a link to the easiest way.
http://www.ebay.com/itm/Speedometer-...a9a888&vxp=mtr

[Shaun1162]

Originally Posted by geezer#99

Here's a link to the easiest way.
http://www.ebay.com/itm/Speedometer-...a9a888&vxp=mtr

Thanks, looks to be just what I needed... Didn't know they made those brand new anymore

[LockDoc]

Originally Posted by Shaun1162

Thanks, looks to be just what I needed... Didn't know they made those brand new anymore

They are listed in the first link that 48richard posted also.

LockDoc

[Shaun1162]

Originally Posted by LockDoc

They are listed in the first link that 48richard posted also.

LockDoc

Yep, my bad, guess I just scrolled over the section on the adapters a little too fast