Speedometer Needle Bouncing around.
More Turbo
Joined: Nov 2019
Posts: 542
Likes: 72
From: Point Washington
Not your year truck 81 F100.
Little back story when I got the truck on the road back in Nov 2019 the speedo did not work, found the drive gear on the out put shaft stripped.
When I replaced it I also replaced the driven gear and it worked and was on the money based on my GPS and mile markers and good for 4000+ miles.
Forward to last weekend when I swapped out the BW T18 for a NP435 and added an Advance Adaptor over drive unit.
Because the trans is moved back 7.5 inches the speedo cable was stretched to fit in the trans.
On a test drive the needle bounced where it did not before being stretched and of unknown drive gear. I found this drive gear was worn a little more than I liked.
I was able to get a longer cable, reusing the driven gear on it and I swapped the drive gears on the trans.
The speedo now works as it did before the trans swap & OD unit.
So I would say make sure the cable is not making any sharp bends, I lubed the new cable with Redline MT-90 gear oil I poured down the cable before I installed it and that the drive gear on the trans is in good shape.
I don't know if it was the cable or the drive gear that fixed it but it is working like the factory had it.
Good luck
Dave ----
Little back story when I got the truck on the road back in Nov 2019 the speedo did not work, found the drive gear on the out put shaft stripped.
When I replaced it I also replaced the driven gear and it worked and was on the money based on my GPS and mile markers and good for 4000+ miles.
Forward to last weekend when I swapped out the BW T18 for a NP435 and added an Advance Adaptor over drive unit.
Because the trans is moved back 7.5 inches the speedo cable was stretched to fit in the trans.
On a test drive the needle bounced where it did not before being stretched and of unknown drive gear. I found this drive gear was worn a little more than I liked.
I was able to get a longer cable, reusing the driven gear on it and I swapped the drive gears on the trans.
The speedo now works as it did before the trans swap & OD unit.
So I would say make sure the cable is not making any sharp bends, I lubed the new cable with Redline MT-90 gear oil I poured down the cable before I installed it and that the drive gear on the trans is in good shape.
I don't know if it was the cable or the drive gear that fixed it but it is working like the factory had it.
Good luck
Dave ----
Logistics Pro
Joined: Dec 2004
Posts: 4,651
Likes: 60
From: Hemet ca.
On any speedometer cable I have installed I use a mixture of white lithium grease and transmission fluid. a 50/50 mix in a container. Then using a drill on one end of cable, the other in the mixture run the drill forward and reverse until cable is lubricated.
When installing make sure it's a smooth fit with NO sharp bends. At least now you eliminate the cable issue.
When installing make sure it's a smooth fit with NO sharp bends. At least now you eliminate the cable issue.
Mountain Pass
Joined: Jun 2009
Posts: 112
Likes: 0
From: Cheyenne, Wyoming
What is the best way to access to speedometer cable to lubricate it. I tried reaching up behind the dash and could not get to the cable at the speedo head. Do I need to unscrew the dash board assembly?
My parts guy suggested a light sewing machine oil, and then sold me dry graphite spray. Suggestions on the best lube? A mix of 3 in 1 oil and graphite?
My parts guy suggested a light sewing machine oil, and then sold me dry graphite spray. Suggestions on the best lube? A mix of 3 in 1 oil and graphite?
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