advice for speedo not working thx (1 Viewer)

[peiserg]

Had my 9/1975 stock drivetrain fj40 tranny and TC rebuilt. Upon receipt of vehicle the speedo worked erratically for a short period before giving up the ghost. I had tech put in brand new speedo gear (same # of teeth that was removed...18). New speedo worked for maybe 30 miles normally. Then quickly also became jerky, erratic and quickly stopped working. New gear is chewed up like old gear.

Rebuild guy first says its a bad cable. I point out i replaced the cable before replacing the speedo gear, so the cable is brand new.

then he said is probably the speedo in dash unit itself, not the TC. He said if the in dash unit is catching, it will cause the cable to catch as well (obviously) and transmit the problem to the new speedo gear causing failure. I pointed out the speedo has worked every single day of the 27 years i've had the truck, up to and including when i dropped it off.

anyway. I've ordered another new 18 tooth gear. he wants to put it in without engaging the cable, to rule out the in dash display as the culprit. Is there a "trick" to ensuring the gear is smoothly engaged in the TC? Keep in mind the TC was freshly removed and rebuilt.

thanks.

 

[reddingcruiser]

You can use a variable speed drill to drive the lower end of the speedo cable. If the speedo needle operates smoothly then your problem is likely on the drive gear assembly. Have you pulled the p-brake drum and rear cover to assess the condition of the driving gear on the main shaft (i.e. no burrs or damage)? Is the order correct; spacer, drive gear, parking brake drum?

 

[Poser]

If the drive gear in the transfer case is not compatible with the driven gear, it will be chewed up, every time.

There are number sets on both the drive and driven gear, example, 8x17 8x18, etc.

In order to see the number on the drive gear, you will need to remove the rear output housing seal(behind the emergency brake backing plate), and use a telescoping magnet to pull it out.

 

[peiserg]

The replacement Speedo gear I put in was the same number of teeth as the one I pulled out, 18. So assuming it has the same number of teeth is there some other measurement that could be different? Or is there some other potential source of chewing up the gear

 

[Awl_TEQ]

Nice Timing with this post. My speedo quit too. Gauge is fine and the cable seems to spin freely. No time to check the drive gears until after this weekend's winter wheeling.

 

[John McVicker]

The replacement Speedo gear I put in was the same number of teeth as the one I pulled out, 18. So assuming it has the same number of teeth is there some other measurement that could be different? Or is there some other potential source of chewing up the gear

Sounds like both speedo gears you installed were the same as each other...but...evidently not the same as the 'drive gear' that turns the cable.

Think I would reread Poser's comment & check your 'drive gear' count and match that up with your next speedo cable.

 

[Solace in Solitude]

Sounds like both speedo gears you installed were the same as each other...but...evidently not the same as the 'drive gear' that turns the cable.

Think I would reread Poser's comment & check your 'drive gear' count and match that up with your next speedo cable.

^^X2^^

Do as @Poser suggests... The fact that your original and replacement were both chewed up, sounds like it had the wrong cable when you bought it.

 

[peiserg]

Ok thanks for into... But i guess what has me slightly confused is with the initial rebuild I did not replace the speedo gear. I just put the old one back in. Or I should say the shop put the old one back in. So it had the original gear that's been in there for a decade and working just fine. I'm wondering if the rebuild kit from Spectre included a different size driving gear?

 

[Solace in Solitude]

Ok thanks for into... But i guess what has me slightly confused is with the initial rebuild I did not replace the speedo gear. I just put the old one back in. Or I should say the shop put the old one back in. So it had the original gear that's been in there for a decade and working just fine. I'm wondering if the rebuild kit from Spectre included a different size driving gear?

Dunno.


You'll need to compare the numbers.

 

[carreta]

I'm in the process of replacing the driven gear too. If I understood what @Poser said is that the problem with @peiserg is that the driven gear is different than the drive gear. then his problem isn't the cable because according to the manual the cable is always the same. Am I correct?

Thanks

Alvaro

 

[tornadoalleycruiser]

Driven gear in tcase might be installed backwards

 

[peiserg]

If the drive gear in the transfer case is not compatible with the driven gear, it will be chewed up, every time.

There are number sets on both the drive and driven gear, example, 8x17 8x18, etc.

In order to see the number on the drive gear, you will need to remove the rear output housing seal(behind the emergency brake backing plate), and use a telescoping magnet to pull it out.

Is this a difficult maneuver without pulling the transfer case? Ill ask the tech to do whar you suggest as im leery of pulling parts out of my transfercase.

 

[sggoat]

Had my 9/1975 stock drivetrain fj40 tranny and TC rebuilt. Upon receipt of vehicle the speedo worked erratically for a short period before giving up the ghost. I had tech put in brand new speedo gear (same # of teeth that was removed...18). New speedo worked for maybe 30 miles normally. Then quickly also became jerky, erratic and quickly stopped working. New gear is chewed up like old gear.

Rebuild guy first says its a bad cable. I point out i replaced the cable before replacing the speedo gear, so the cable is brand new.

then he said is probably the speedo in dash unit itself, not the TC. He said if the in dash unit is catching, it will cause the cable to catch as well (obviously) and transmit the problem to the new speedo gear causing failure. I pointed out the speedo has worked every single day of the 27 years i've had the truck, up to and including when i dropped it off.

anyway. I've ordered another new 18 tooth gear. he wants to put it in without engaging the cable, to rule out the in dash display as the culprit. Is there a "trick" to ensuring the gear is smoothly engaged in the TC? Keep in mind the TC was freshly removed and rebuilt.

thanks.

Based on the avoidance you have already gotten from this person, I would install the thing myself.

 

[peiserg]

as an update. tranny and TC rebuild shop think my tech (different shop) who did the RnR of the unit, including putting back on of the parking brake, did not shim the unit correctly, allowing movement of the driving gear for the speedo when under load. I ordered a shim set from SOR. hopefully that will do the trick. This isn't the first time i've regretted using more than one shop at the same time for a repair.