Speedo gears from scratch - The 1947 - Present Chevrolet & GMC Truck Message Board Network

PanelDeland · 11-12-2014, 11:10 AM

Left the NC gathering of the Goofs sat afternoon and as I merged onto the interstate, my speedo quit. So yesterday I was going to pull the driven gear and inspect it to see what was going on. There wasn't one. I'm sure it's in the tailhousing. So I'll be pulling that to get the old gear/pieces out. Since I have no idea of the gear count on any of it,I would like to just order new drive, driven gears and all the seals and clips etc. I figure I might as well replace all of it while I'm in there. So how do I determine the gears I need from scratch?

**LockDoc** · 11-12-2014, 11:20 AM

Quote:

Originally Posted by PanelDeland

Left the NC gathering of the Goofs sat afternoon and as I merged onto the interstate, my speedo quit. So yesterday I was going to pull the driven gear and inspect it to see what was going on. There wasn't one. I'm sure it's in the tailhousing. So I'll be pulling that to get the old gear/pieces out. Since I have no idea of the gear count on any of it,I would like to just order new drive, driven gears and all the seals and clips etc. I figure I might as well replace all of it while I'm in there. So how do I determine the gears I need from scratch?

You should be able to tell from the color of the plastic that the gear is made from and the color of the gear on the output shaft.. Check this site out:

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

There is also a chart down a ways that you can use to calculate what you need.

LockDoc

PanelDeland · 11-12-2014, 12:04 PM

Good info LockDoc. Unfortunately I don't know the color of either. I was hoping to order all new seal, gears, and clips and just replace everything in there in one sitting (or laying).I wasn't wanting to have it apart while I waited on parts.

**LockDoc** · 11-12-2014, 05:56 PM

Quote:

Originally Posted by PanelDeland

Good info LockDoc. Unfortunately I don't know the color of either. I was hoping to order all new seal, gears, and clips and just replace everything in there in one sitting (or laying).I wasn't wanting to have it apart while I waited on parts.

I'm not sure how you could do that and be 100% sure of getting the correct parts the first time....

LockDoc

mechanicalman · 11-12-2014, 06:50 PM

Quote:

Originally Posted by PanelDeland

Left the NC gathering of the Goofs sat afternoon and as I merged onto the interstate, my speedo quit. So yesterday I was going to pull the driven gear and inspect it to see what was going on. There wasn't one. I'm sure it's in the tailhousing. So I'll be pulling that to get the old gear/pieces out. Since I have no idea of the gear count on any of it,I would like to just order new drive, driven gears and all the seals and clips etc. I figure I might as well replace all of it while I'm in there. So how do I determine the gears I need from scratch?

http://www.tciauto.com/tc/speedometer-gear-calculator/

71meangreenc10 · 11-12-2014, 06:56 PM

Deland,

What trans are you running? I have built both types. The PATC site is a good one to use, plus they have a lot of parts in stock.

Smitty

davepl · 11-12-2014, 08:17 PM

I see it says:

"All 2004R transmissions use a 1" diameter steel driven gear housing."

What does that mean to me in practical terms, since I have a 200-4R I'll need to calibrate? I can read, so I know the driven gear is 1" in diameter and made of steel, but there's no mention of how many teeth or anything.

mechanicalman · 11-12-2014, 09:10 PM

Quote:

Originally Posted by davepl

I see it says:

"All 2004R transmissions use a 1" diameter steel driven gear housing."

What does that mean to me in practical terms, since I have a 200-4R I'll need to calibrate? I can read, so I know the driven gear is 1" in diameter and made of steel, but there's no mention of how many teeth or anything.

It means very little, it just refers to the "bullet" that holts the driven gear into the housing. Not well worded, it means the housing is steel, but sounds like it means the gear is steel but it's plastic. Refer to this link for pictures of the driven gears and 1" steel housing.
https://www.google.com/search?q=2004...0QsAQ&dpr=0.95

PanelDeland · 11-12-2014, 10:08 PM

Had a brain Fart. I figured it out. I'm going to use the calc and just plug in a random drive gear and see what the calc shows. I may have to try more than once but some combo has to be right and then I'll order what has the least percentage of variation.

BTW it's a Saginaw 3 speed.

11-12-2014, 11:10 AM	#1
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Speedo gears from scratch Left the NC gathering of the Goofs sat afternoon and as I merged onto the interstate, my speedo quit. So yesterday I was going to pull the driven gear and inspect it to see what was going on. There wasn't one. I'm sure it's in the tailhousing. So I'll be pulling that to get the old gear/pieces out. Since I have no idea of the gear count on any of it,I would like to just order new drive, driven gears and all the seals and clips etc. I figure I might as well replace all of it while I'm in there. So how do I determine the gears I need from scratch? __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

11-12-2014, 12:04 PM	#3
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: Speedo gears from scratch Good info LockDoc. Unfortunately I don't know the color of either. I was hoping to order all new seal, gears, and clips and just replace everything in there in one sitting (or laying).I wasn't wanting to have it apart while I waited on parts. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

11-12-2014, 06:56 PM	#6
71meangreenc10 Its a Truck Thing...... Join Date: Dec 2004 Location: Sierra Vista, Arizona Posts: 3,179	Re: Speedo gears from scratch Deland, What trans are you running? I have built both types. The PATC site is a good one to use, plus they have a lot of parts in stock. Smitty __________________ 71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 69 C30 Former Motor Home, Flat Bed time 70 G20 Red-E-Kamp Conversion "I'm your Boogy Van"

11-12-2014, 08:17 PM	#7
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: Speedo gears from scratch I see it says: "All 2004R transmissions use a 1" diameter steel driven gear housing." What does that mean to me in practical terms, since I have a 200-4R I'll need to calibrate? I can read, so I know the driven gear is 1" in diameter and made of steel, but there's no mention of how many teeth or anything. __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible

11-12-2014, 10:08 PM	#9
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: Speedo gears from scratch Had a brain Fart. I figured it out. I'm going to use the calc and just plug in a random drive gear and see what the calc shows. I may have to try more than once but some combo has to be right and then I'll order what has the least percentage of variation. BTW it's a Saginaw 3 speed. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil" Last edited by PanelDeland; 11-12-2014 at 10:14 PM.

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