Speedometer Gear Combinations

R

RoadWarrior

Active member
Apr 8, 2017
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OK, my PO added the 3.70 gears to my coach (can't hate him for that). I want to get my speedometer to read correctly and was wondering what
speedometer drive, and driven gear combinations anyone has used successfully?
 
There is a gearbox that Jim K. supplies with the new ratio final drive that
mounts on the speedometer drive that changes the gear ratio to feed the
speedometer IF NO ONE HAS MESSED WITH the original gears that came with the
3:07 final drive and stock TM-425. Give him a call to see what you might
have available.
Jim Hupy
Salem, OR
78 GMC Royale 403 w/3:70 final drive and the corrected speedometer gearbox.

> OK, my PO added the 3.70 gears to my coach (can't hate him for that). I
> want to get my speedometer to read correctly and was wondering what
> speedometer drive, and driven gear combinations anyone has used
> successfully?
>
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>
 
> OK, my PO added the 3.70 gears to my coach (can't hate him for that). I want to get my speedometer to read correctly and was wondering what
> speedometer drive, and driven gear combinations anyone has used successfully?
http://www.appliedgmc.com/prod.itml/icOid/1374
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"Every day I become more convinced that I am the only person left on the planet that recognizes nonsense for what it is."
 
I know that option is available, but it isn't a big job to pull the governor and replace the speedometer drive gear. Also, that little reducer is
likely to get cooked by the heat of the headers.
 
I have been running one of them for a long time (years) with two cross
country trips included. I run Doug Thorley Headers on a 403 Olds with a
heavy 78 Royale Coach frequently pulling a trailer. No problems yet with
the gearbox. I am not sure that you can get the exact gear any longer that
will be spot on with only one gear changed if you go into the transmission.
But, Jim K can tell you for sure, and he has a toll free phone number. All
it will cost you is your time. If you are running headers and they are not
the Manny T ones, you will have to pull the headers on that side of the
engine to pull the governor. But, it is your time and money, and this is
America, land of the Free Choices.
Jim Hupy
Salem, OR
78 GMC Royale 403

> I know that option is available, but it isn't a big job to pull the
> governor and replace the speedometer drive gear. Also, that little reducer
> is
> likely to get cooked by the heat of the headers.
>
>
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> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
 
We carry the reducers as we need to supply them with our 3.55,3.70,4.10 and Limited Slip Differentials

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________________________________
From: Gmclist on behalf of David H.Jarvis
Sent: Thursday, April 27, 2017 2:55:36 PM
To: gmclist
Subject: Re: [GMCnet] Speedometer Gear Combinations

There was a lad in Florida that had gear reducers for this purpose.
Try Ron 727 410 6352

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No need to disturb the Gov to remove the speedo gear.

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________________________________
From: Gmclist on behalf of John Watkins
Sent: Thursday, April 27, 2017 2:05:10 PM
To: gmclist
Subject: Re: [GMCnet] Speedometer Gear Combinations

I know that option is available, but it isn't a big job to pull the governor and replace the speedometer drive gear. Also, that little reducer is
likely to get cooked by the heat of the headers.

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Headers do not do much to damage the gear.
Heat effects the cable and jams up and strips the gear.
Know this from working on coaches

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________________________________
From: Gmclist on behalf of John Watkins
Sent: Thursday, April 27, 2017 2:05:10 PM
To: gmclist
Subject: Re: [GMCnet] Speedometer Gear Combinations

I know that option is available, but it isn't a big job to pull the governor and replace the speedometer drive gear. Also, that little reducer is
likely to get cooked by the heat of the headers.

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We end up supplying special ratio when people make changes without knowing

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________________________________
From: Gmclist on behalf of James Hupy
Sent: Thursday, April 27, 2017 1:51:23 PM
To: gmclist
Subject: Re: [GMCnet] Speedometer Gear Combinations

There is a gearbox that Jim K. supplies with the new ratio final drive that
mounts on the speedometer drive that changes the gear ratio to feed the
speedometer IF NO ONE HAS MESSED WITH the original gears that came with the
3:07 final drive and stock TM-425. Give him a call to see what you might
have available.
Jim Hupy
Salem, OR
78 GMC Royale 403 w/3:70 final drive and the corrected speedometer gearbox.

> OK, my PO added the 3.70 gears to my coach (can't hate him for that). I
> want to get my speedometer to read correctly and was wondering what
> speedometer drive, and driven gear combinations anyone has used
> successfully?
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
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Just call me and I will get data from you and supply the correct ratio

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________________________________
From: Gmclist on behalf of John Watkins
Sent: Thursday, April 27, 2017 1:44:36 PM
To: gmclist
Subject: [GMCnet] Speedometer Gear Combinations

OK, my PO added the 3.70 gears to my coach (can't hate him for that). I want to get my speedometer to read correctly and was wondering what
speedometer drive, and driven gear combinations anyone has used successfully?

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GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Just call me as we can solve it

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________________________________
From: Gmclist on behalf of John Watkins
Sent: Thursday, April 27, 2017 1:44:36 PM
To: gmclist
Subject: [GMCnet] Speedometer Gear Combinations

OK, my PO added the 3.70 gears to my coach (can't hate him for that). I want to get my speedometer to read correctly and was wondering what
speedometer drive, and driven gear combinations anyone has used successfully?

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
I ordered heat shield tubing, I believe from Sunmmit or Jegs their private brand less expensive different sizes available, and put around speedo
cables and anything in the area of the headers, so far so good after I melted down a speedo cable.
Skip Hartline
 
You need to strap the cable away from the exaust

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________________________________
From: Gmclist on behalf of Skip Hartline
Sent: Friday, April 28, 2017 6:12:51 AM
To: gmclist
Subject: Re: [GMCnet] Speedometer Gear Combinations

I ordered heat shield tubing, I believe from Sunmmit or Jegs their private brand less expensive different sizes available, and put around speedo
cables and anything in the area of the headers, so far so good after I melted down a speedo cable.
Skip Hartline

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I don't think you want to change the governor gear. If you do that, you will be moving the shift points up the engine's torque curve and that is one
thing you really don't want to do as it would negate some of the value of the higher numerical ratio final drive.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Still Loving OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
I picked up a Garmin GPS on sale for something like $129 a few years ago.
It has a very precise digital speedometer. Additionally, for most roads
(90%+) it displays the speed limits as well. It also can calculate routes,
AND does a pretty good job of keeping me on the correct roads.

Hugs,
Vern

Currently at the GMC Classics Rally in Bandera, Texas

> These GPS Speedo's are pricey, but sure work nice,
>
>
> https://www.horsepowerfreaks.com/-p-150899736.html?gclid=CNfnvO_Xx9MCFddWDQodQGsOzA
> --
> Larry
> 78 Royale w/500 Caddy
> Menomonie, WI.
>
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--
Vern Crawford
2013-2014 Past-President
Hill Country Chapter http://txmn.org/hillcountry/
Texas Master Naturalist

155 J-J Lane
Center Point, TX 78010
(830) 634-2576 home
(618) 203-8296 cell
VernCrawford

[image: Texas Master Naturalist_small]
 
I at least need to inspect the governor drive gear (speedometer bouncing). The speedometer "Drive" gear is at the top of the governor, not the one at
the bottom and only drives the speedometer "Driven) gear. The speedometer gears don't affect shift points. Other than the speedometers reading.
 
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