Speedometer gears. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

PanelDeland · 08-10-2017, 11:37 AM

I'm having a speedo problem. I replaced the driven gear Old one is gone) to correct the speedometer but I've had 2 strip (the gears on the driven one). Is there an incompatability problem with the drive and driven gears. I don't really want to go into the tranny but may have to, to correct this. I know there are at least 2 maybe 3 drive gears for this and was wondering if maybe the green driven gear doesn't work with one of the others? It's a 68 3 speed on the column if it makes a difference and from what I've found, they are the same as a Powerglide as far as speedometer gears. Any help or a link to a chart that actually tells me something would be good.

geezer#99 · 08-10-2017, 12:19 PM

You might find what you need in here.
https://transmissioncenter.net/shop/

snipescastle2 · 08-15-2017, 01:14 PM

Sorry didn't realize it was three on the tree

silverstreak · 08-17-2017, 08:02 PM

What does the drive gear look like? Are the teeth worn to the point of chewing up the teeth on the driven gear? Is the speedo cable kinked causing it to seize up or hard to rotate in it's casining / jacket?

**HO455** · 08-17-2017, 11:37 PM

There are different housings for the gears. When you changed from your original gear to the new one it is likely that your original housing is no longer correct. If I am not mistaken there should be 3-4 two digit numbers cast into the housing i.e. 41 42 43 44. These indicate what driven gears work in that particular housing. As the diameter of the gears change with the number of teeth on the gear the hole in the center of the housing has to change its relationship with the drive gear. Using too small of a gear means you don't have enough contact between the teeth or no contact at all. Using too big of a gear means you used a BFH to install it.

Summit and Jegs sell the housings
Or if you go to an old dealership parts department and they will have the original parts "BOOKS" with the speedometer gear applications which are literally tens of pages of wheel/tire combinations to rear end ratios for each transmission. I had to get new one a year ago and I took some donuts into the Wentworth Chevy parts department and got to go through and find what I needed.

08-10-2017, 11:37 AM	#1
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,992	Speedometer gears. I'm having a speedo problem. I replaced the driven gear Old one is gone) to correct the speedometer but I've had 2 strip (the gears on the driven one). Is there an incompatability problem with the drive and driven gears. I don't really want to go into the tranny but may have to, to correct this. I know there are at least 2 maybe 3 drive gears for this and was wondering if maybe the green driven gear doesn't work with one of the others? It's a 68 3 speed on the column if it makes a difference and from what I've found, they are the same as a Powerglide as far as speedometer gears. Any help or a link to a chart that actually tells me something would be good. __________________ 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"

08-10-2017, 12:19 PM	#2
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,731	Re: Speedometer gears. You might find what you need in here. https://transmissioncenter.net/shop/

08-15-2017, 01:14 PM	#3
snipescastle2 Registered User Join Date: Mar 2009 Location: WARRENSBURG,MISSOURI,64093 Posts: 1,518	Re: Speedometer gears. Sorry didn't realize it was three on the tree __________________ "Persistence is the twin sister of Excellence.one is a matter of quality,the other, a matter of time" “Serious Black” my 1971 Short Bed Fleetside Sold to an outstanding man in Lees Summit,Mo. “Gone, but by no means,Forgotten” Last edited by snipescastle2; 08-15-2017 at 01:17 PM. Reason: Mistake

08-17-2017, 08:02 PM	#4
silverstreak Registered User Join Date: Mar 2009 Location: USA Posts: 255	Re: Speedometer gears. What does the drive gear look like? Are the teeth worn to the point of chewing up the teeth on the driven gear? Is the speedo cable kinked causing it to seize up or hard to rotate in it's casining / jacket?

08-17-2017, 11:37 PM	#5
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 11,350	Re: Speedometer gears. There are different housings for the gears. When you changed from your original gear to the new one it is likely that your original housing is no longer correct. If I am not mistaken there should be 3-4 two digit numbers cast into the housing i.e. 41 42 43 44. These indicate what driven gears work in that particular housing. As the diameter of the gears change with the number of teeth on the gear the hole in the center of the housing has to change its relationship with the drive gear. Using too small of a gear means you don't have enough contact between the teeth or no contact at all. Using too big of a gear means you used a BFH to install it. Summit and Jegs sell the housings Or if you go to an old dealership parts department and they will have the original parts "BOOKS" with the speedometer gear applications which are literally tens of pages of wheel/tire combinations to rear end ratios for each transmission. I had to get new one a year ago and I took some donuts into the Wentworth Chevy parts department and got to go through and find what I needed. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 Last edited by HO455; 08-17-2017 at 11:46 PM.



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