plastic gear in tranny to hook up speedo.?
 

not too up on tranny's, but i have been told of a plastic gear of some type that is under a plate where your speedo cable hooks into your tranny. anyone know what i'm talkin' 'bout? this is on a th350.also i unhooked the cable at both ends to make sure i didn't have a dry cable tubing.it looked brand new and had plenty of lubrication.when i first got it,it used to bounce a lot.now it don't do nothin'.where can i get one of those plastic gears(if thats what it is), and how much do they run?speedo itself works fine.

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'68 swb 350/350 w/edelbrock total performance-performer pkg.ceramic headers,2.5" delta-flow 40 series flowmstrs.no rust of the notorious mid-west on this one! see my truck at free photo-i under "'68 chevy truck"

Go to any trans. shop and they should have the gear, and will install it. You need to find out which gear you need also for calb. the speedo when done. The gear itself isn't that much, but having it installed maybe inless you can do it, are have someone you know do it.

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Andy
71's Are for ever!!! or 67,68,69,70,72
71,factory tach,tilt for straight drive,gauges,ac,305 HO TPI with 700-R4 lowered,17" wheels




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Chevy dealers should have them in stock. Remove yours and take it with you. If you speedometer has been accurate, simply match it up with a new one. There are different colors which have a different amount of teeth.

If your speedometer is not accurate, then it's a matter of trying different gears until it reads correctly. For that, I would recommend a shop as they should have plenty of good used ones laying around for just this reason. Beats buying 4 new ones!

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63 Impala*66 Chevelle SS*69 Chevelle*69 C10 Stepside*71 Cheyenne 20*72 Chevelle

Parts for sale:
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thanks bob,andy,i'll do that this next wk.then!

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'68 swb 350/350 w/edelbrock total performance-performer pkg.ceramic headers,2.5" delta-flow 40 series flowmstrs.no rust of the notorious mid-west on this one! see my truck at free photo-i under "'68 chevy truck"

However, if your needle was bouncing, then stopped working, you are probably looking at a busted cable.
Have a helper in the cab watching the speedo while you lay under spinning the disconnected cable. If the speedo don't move, it's a cable.When the cable gets old, it gets springy and causes the bounce you described.

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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite.
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Andy, in Columbus Ohio

If the cable is bounceing it needs to be lubed. Dont use greese because the first cold day wil snap the cable. Use speedo cable lube (very light oil with grafite)

There are two plastic gears involved,,the drive gear and the driven gear. The driven gear is simple to change, the drive gear is a little more work. My guess is your cable is at fault. If you want to check the condition of the gears you can back up on to a pair of ramps or jack up and secure the rear half of the truck with jack stands. By lifting the rear up instead of the front you won't lose much, if any ATF. Disconnect speedo cable from trans, remove the bolt and the clamp that holds gear housing into trans and gently pull unit out from trans. Make note of the position of gear housing in relation to the clamp for reinstallation. This will get you to the driven speedo gear. The drive gear requires removing the driveshaft, then the tailshaft extension housing from the trans. This will expose the drive gear,,which is removed by releasing a spring clip and sliding the gear off the output shaft.

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1971 C10 swb stepside 350/700R4/3.73posi
Killingworth, Connecticut

thanks guys,i noticed that when i first got the truck the speedo was working, jumping, but barely working.since i disconnected both ends and pulled the cable completely out of the cable line housing,cleaned it, inspected it,and sprayed it w/a industrial type graphite spray,and reinstalled it,now nothing happens.before it would at least jump at 'round 35-40mph.thats what led me to believe that a plastic or a wear-prone- intended part had failed.i'm goin' to take it to a local tranny shop and let him check it out. at least now i have somethin' i can point him toward to look at.thanks again!