speedo gear in tranny? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BUXMAN66 · 09-02-2002, 11:50 PM

put in a brand new speedometer,new speedo cbl.,checked the gear beside the cbl.input at the tranny for gear wear.still the speedo. doesn't work,except at high speed,and then all it reads is 15-25mph intermittently.doesn't the speedo gear mesh w/the output shaft gear to turn the speedo gear and on to the speedo cbl.?? what gives here?is not the 2 gears meshing together properly,or does this make any sense at all!?!thanks,guys!

*Fast68Chevy* · 09-03-2002, 02:02 AM

is probably cable engagement or speedo unit problem, unless you have way wrong diameter of gears in the tailshaft of tranny.. but if that was the case then you would think the speedo neede would ever move at all ever.,

good luck

*Zkast* · 09-03-2002, 02:15 AM

Remove the cable from the transmission then chuck a drill (brill

) to the drive (center part of the cable) Spin it as fast as the drill will go, somewhere around 2200rpm or higher and the speedo should respond. If you have a new drive and driven gear and cable but it still doesnt work, it sounds like you have a speedo head going out.

If you can get the speedo to respond smoothly, now its time to find out what gear is causing the trouble. Install the cable at the trans, unhook it at the speedo then either jack up the rear wheels or drive it around the block. Feel for catches or no drive at all. If the cable feels ok and the driven gear looks ok (not dished out) then you need to take a VERY good look at the drive gear. It can wear evenly and appear to be ok when in fact its not tall enough to contact the driven gear. Also check for excessive tailshaft/drive shaft movement.

BUXMAN66 · 09-03-2002, 11:55 AM

i have a brand new speedo head unit from pauls,so i'd think it wouldn't be that. it sounds kinda goofy but when you attach the drill(brill!!lol) what is the normal forward motion to drive the speedo unit ?would that be clock-wise w/ the drill or counter-clockwise?thanks,buxman66.

BUXMAN66 · 09-03-2002, 11:59 AM

imho,i think the speedo gear is not tall enuff to contact the drive shaft gear.how do i replace/remedy this?(short of taking it to the tranny shop and puttin' it up on the lift)??

da-burb · 09-03-2002, 12:28 PM

Is it possible that somebody changed out the gears without changing the retaining plate? If you take the cover off of your speedo driven gear it will have a number range on it. The last one I looked at was 40-42. That means it is to be used with a gear that has 40, 41, or 42 teeth on it. If you tried a 36 tooth gear in there it wouldn't be positioned correctly to engage the drive gear.

BUXMAN66 · 09-04-2002, 01:20 AM

thanks,burb i'll check on that. 'preceiate the input!buxman66.

09-02-2002, 11:50 PM	#1
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	speedo gear in tranny? put in a brand new speedometer,new speedo cbl.,checked the gear beside the cbl.input at the tranny for gear wear.still the speedo. doesn't work,except at high speed,and then all it reads is 15-25mph intermittently.doesn't the speedo gear mesh w/the output shaft gear to turn the speedo gear and on to the speedo cbl.?? what gives here?is not the 2 gears meshing together properly,or does this make any sense at all!?!thanks,guys! __________________ '68 swb 1/2t 350/350th '86 lngbd 3/4 TON parts getter '49 gmc 1/2 t 5 window 350/350th '96 gmc sonoma sle ext-cab. hey it's a 4cyl. 5 spd and good on gas y'know?

09-03-2002, 11:55 AM	#4
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	i have a brand new speedo head unit from pauls,so i'd think it wouldn't be that. it sounds kinda goofy but when you attach the drill(brill!!lol) what is the normal forward motion to drive the speedo unit ?would that be clock-wise w/ the drill or counter-clockwise?thanks,buxman66. __________________ '68 swb 1/2t 350/350th '86 lngbd 3/4 TON parts getter '49 gmc 1/2 t 5 window 350/350th '96 gmc sonoma sle ext-cab. hey it's a 4cyl. 5 spd and good on gas y'know?

09-03-2002, 11:59 AM	#5
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	imho,i think the speedo gear is not tall enuff to contact the drive shaft gear.how do i replace/remedy this?(short of taking it to the tranny shop and puttin' it up on the lift)?? __________________ '68 swb 1/2t 350/350th '86 lngbd 3/4 TON parts getter '49 gmc 1/2 t 5 window 350/350th '96 gmc sonoma sle ext-cab. hey it's a 4cyl. 5 spd and good on gas y'know?

09-03-2002, 12:28 PM	#6
da-burb "Ochre Ogre" Join Date: Apr 2000 Location: Springfield, MN Posts: 3,558	Is it possible that somebody changed out the gears without changing the retaining plate? If you take the cover off of your speedo driven gear it will have a number range on it. The last one I looked at was 40-42. That means it is to be used with a gear that has 40, 41, or 42 teeth on it. If you tried a 36 tooth gear in there it wouldn't be positioned correctly to engage the drive gear. __________________ Bowtie Truck Stop Inc. Mid-West GM Truck Restoration Parts Supplier Your Key Parts, Auto Metal Direct, Dynacorn, and Goodmark dealer. like us @ www.facebook.com/BowtieTruckStop 1971 C-10 Suburban (Ochre) 1971 K-10 Suburban (Ochre) 1972 C-10 Suburban (Ochre) 1972 K-20 Suburban (Yellow- that just aint right!) Springfield, Minnesota 56087

09-03-2002, 02:02 AM	#2
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	is probably cable engagement or speedo unit problem, unless you have way wrong diameter of gears in the tailshaft of tranny.. but if that was the case then you would think the speedo neede would ever move at all ever., good luck

09-03-2002, 02:15 AM	#3
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	Remove the cable from the transmission then chuck a drill (brill ) to the drive (center part of the cable) Spin it as fast as the drill will go, somewhere around 2200rpm or higher and the speedo should respond. If you have a new drive and driven gear and cable but it still doesnt work, it sounds like you have a speedo head going out. If you can get the speedo to respond smoothly, now its time to find out what gear is causing the trouble. Install the cable at the trans, unhook it at the speedo then either jack up the rear wheels or drive it around the block. Feel for catches or no drive at all. If the cable feels ok and the driven gear looks ok (not dished out) then you need to take a VERY good look at the drive gear. It can wear evenly and appear to be ok when in fact its not tall enough to contact the driven gear. Also check for excessive tailshaft/drive shaft movement.

09-04-2002, 01:20 AM	#7
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	thanks,burb i'll check on that. 'preceiate the input!buxman66.



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