Speedometer gauge question
 

1970 c10
The speedo guage in my truck is off (too slow) by around 12 mph.
Got new drive gears for the TH350 trans and tried one several teeth higher.
Didn't change the gauge at all. Still off the same mph
The needle bounces a bit so I'm guessing the magnets in the gauge are weak or something wrong internal in the gauge.
Can those be rebuild or just replace the whole gauge?
Thanks. Mark

Bouncy Speedometer Needle
 

I'd fix that dry speedo cable first.....

The center is easily withdrawn then cleaned and re lubed as you slide it back in .

Sorry. Forgot to mention. The cable is new.
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Speedometer Gear
 

Reading further into this I realize you're past that now and will prolly discover the gear and spacer were reversed in positions per your photo and the various factory diagrams .

When you go to re assemble the roller bearings, first wipe of all the oil oil and use the stickiest grease you can find, slather grease on the race them place the rollers in place and make sure there's NO GAP, then smear a bit more grease on top of the rollers to ensure they don't fall out as you're inserting the shaft .

It's been a few years since I did manual gearbox repair, it's quite simple as you'll soon see .

I'm curious to see why the gear isn't easily removable and I too think that heating it will loosen it up as it's made of Bronze and will expand faster than the shaft it's on .

Re: Speedometer Gear
 

Really, what are you talking about? He has a 2wd with a turbo 350 automatic.

Anyways, check the drive gear inside the trans and see if the teeth are square instead of cupped out and stripped. AND you will be off on calibration by percentage not MPH

Re: Speedometer Gear
 

I'm talking about the clearly shown not centered drive gear Vs. the hole, one can see the spacer to the right when it should (?) be to the left...

We'll see when he gets it all apart .

Re: Speedometer gauge question
 

I;ve gone blind !!

Re: Speedometer gauge question
 

I'll check that tomorrow. Thanks guys.
Yes. It's percentage but for rough idea I drive 30 the gauge shows 20.
I'll follow up with what I find.
I hate reading these and not knowing what the fix was.
Mark

Re: Speedometer gauge question
 

have you put new wheels on it ?

Someone before me converted 6 lug to 5 lug and added added from disc.
I assumed that's why the speedo was off
I bought an assortment of driven gears and was going to try a few before pulling trans tailpiece off to drive gear. Orginal was a 19. Tried a 22 and didn't change at all so that's why I assumed the gauge.
I think VWNate may be posting here by accident. There is a another speedometer post going on here at same time. I haven't posted any photos of this problem.
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Re: Speedometer gauge question
 

whew thats a relief

Re: Speedometer Accuracy TH350
 

Sorry guys .

For speedo adjusting there are still a couple places that sell different plastic driven gears, usually you can buy the set cheaply .

Re: Speedometer gauge question
 

30% is quite a ways off. Gear ratio and tire size determine speed of vehicle. So what are you working with.