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The speedometer went out on my 75 for speed. I pulled the speedometer cable off the connection on the transmission and hooked it up to my drill in reverse and put it on low speed and the speedometer stayed at a steady 30 miles an hour, I move the drill to high-speed and the speedometer stayed at a steady 70 miles an hour so I think I can rule out the cable and speedometer. I ordered new nylon gears and a new nylon gear housing. Put them on and the speedometer moved for a second and back to zero on a test drive.
My next test is to lift rear wheels with cable disconnected put it in gear and see if nylon gear is turning. I will have to wait to get help for that test.
I am fortunate to have a lift so I am not having to jack it up and down and that makes service easier.
Do not run the car with the rear wheels hanging, the half shaft u-joints were not designed for that.
Turn the rear wheels by hand when doing this test.
recheck your new nylon driven gear to see if it instantly stripped out.
did your old nylon gear looked stripped out? eyeball the old and the new and determine that..
if the nylon gear is stripping out then you have a bind in your cable
if the nylon gear is fine then your nylon gear is not engaging onto your speedometer drive gear inside the transmission.
this drive gear is probably also plastic and may be stripped. an original 75 4 speed is a super t-10 but your pic shows a muncie main case so who knows what you have.
get up there with a mirror to see if the drive gear has moved or stripped and if it is metal or plastic.
many muncie speedometer drive gears are plastic held on by a clip that often breaks causing your gear to scoot off the driven gear and the only fix is remove tranny, remove tailhousing, and replace gear with a more durable steel one.
yep.. same thing happened to me.. a weekend of work.....
so I hope you are stripping the driven gear due to a binding cable...
It does have a metal drive gear inside the transmission. I think I would rather drop the transmission than try to replace the cable. The cable seemed fine with the drill test. I did not hear any grinding or strange cable movement. Both the old nylon gear and the new one looks good. I connected a nylon drive gear to the cable and then to the drill and the cable spun good and speedometer worked good.
Thanks for information I will continue to investigate.
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Problem with speedometer 75 4-speed
