Speedo gear (1 Viewer)

[Herb]

I narrowed down the problem of an inoperable speedometer to the speedo gear in the Tcase. So, I purchased the 17 tooth gear from SOR and installed it. The speedo worked great for 5 miles, then stopped. I pulled the plastic speedo gear and it is shredded in one spot and the other teeth are worn down a good bit.

I have some idea of what I think is going on:
I think the 17 teeth is right, because it did work for a bit and because that is what the PO had in it. However, the one the PO had in it was shredded exactly like this one. However, I actually think that something about the speedo gear housing is incorrect...as the gear doesn't spin very freely and there is no way for it to get lubed. It has no notch in it and it has a sleeve that is really wedged down in there. I've opened up another T-Case and obtained another cylinder and gear (THANKS Thornton!) and this setup looks to be more oil flow freindly as it has a notch and a much looser sleeve....and as a result, it spins much more freely.

Could my original, now shredded, part have just frozen up due to friction and heat? Also, just in case I'm putting in the wrong gear, would a tcase that requires an 18 tooth speedo gear shred a 17 tooth...or would it just not spin? Its all guesswork unless I pull the tcase apart and I'm trying to avoid that.

Any insight would be greatly appreciated. Thanks in advance.

Doug

 

[chewy]

Not sure about the cylinder and gear but, you need to check the speedo cable. It may need to be lubed. You can pull the speedo cable out and clean it in a solvent. Then re-lube it with a graphite lubricant. There an actual speedo lube available I'm pretty sure.
An 18 tooth gear should work in place of a 17 tooth. The speedo would be out of calibration. When you change tire sizes or rear end gears it changes your speed in relation to the speedo anyway. Matt

 

[Herb]

Matt, thanks for the reply.

My only concern is that my speedo gears are getting shredded. I think its because they aren't spinning freely in there due to different diameter housings (cylinders) but it might be the driven gear inside the tcase. The speedo cable is new and spins very freely.

Doug

 

[bad_religion_au]

hey, i had a similar problem, kept shredding the speedo gears. mine ended up being a shot bearing in the tcase making everything move. i blew the tcase to figure that out . hope that's not your problem. is your t case making noise?

from my experience, the 18 tooth gear will just throw your speedo out.

 

[Herb]

TCase isn't making any noise...at least that I can tell. All seems fine, 'cept of course for the shredded speedo gears.

Thanks for the insight...I'll keep my ears open for sounds from the Tcase.

 

[pbgbottle]

had the same problem stripped two plastic gears .ended up the gear wasn't fully meshing with the steel gear in the t-case . i ended up pulling the ebrake off, and the steel chunk off the back of the case (retainer,output shaft).inserting the gear and cylinder into that first checking that it rotated freely , and slid it back onto the back of the tcase .and put the ebrake back on and the speedo has worked ever since. not to sure about the tooth count but
there are 4 tooth count options .15,16,17,18 teeth
did some looking and it looks like all the teeth counts will mesh with the speedo gear in the t-case

 

[Herb]

You know, I think I'm going to go that route...and it will give me a chance to see if anything else is goofy inside there. Thanks. BTW, how do you know which tooth count you require?

 

[jhaha]

Herb,

I have the same problem, except I have a 4 speed case and I did have the 18 tooth gear. I don't know for sure if I have the correct gear, it is a long story.

Where are you located? I am in northern Virginia, and would be more than willing to let you try my 18 tooth gear to see if it will fix your problem.

Let me know....

 

[pbgbottle]

not to sure how to tell must have to do with what year your rig is ,what the gear ratio is ,and the stock tire size . i have the part #'s in front of me , but the tooth count varied between wether it was a fj40 ,fj45 ,bj40 ,and if it was a U.S. or canadian what year was yours i can look .. edit i see the year 71

69-74 oem was 17
71-74oem was 16
then list
71-79 18
76-79 CAN 16
79-80 CAN 17
they are all over the place .

 

[Herb]

Jhaha,
I'll PM you and we can talk. Thanks. I have an 18tooth gear already that I think I'm going to try. The only thing is .... if my tcase shredded a 17 tooth, which is smaller, then it seems that it will surely shred the 18 tooth. Maybe I just don't understand how that all works.

 

[Herb]

Pbgbottle,
Wow, they sure are clear aren't they? So, according to the part #s, my 71 could be a 16, 17, or 18. Add the fact that it could be getting shredded simply due to being a bit off in installation...and I may never know. Since the 17 didn't work...twice, I'll try the 18, then the 16.
After that..I think I'll just forget the whole speedometer thing because everything else works - even my parking brake - and I'm just not feeling like tearing into the tcase to figure this out and possibly dorking something else up.

 

[pbgbottle]

i went and looked at my broken case .78 4spd . to see if i could help .i was missing the plastic gear .after looking i probably wouldn't tear it apart either . heres a pic of the metal gear if you haven't seen one . and there only seems to be two part #'s for the metal t-case gear ,would assume they all should mesh but who knows

edit looks like part #33481-60020 likes 18 teeth and
. . #33481-60030 likes 16,17,15,

and you could have either

 

[Herb]

Thanks for the info...that is great! I will just go ahead and try the 18t gear that I have. My vehicle production date is 11/70...but that doesn't mean squat with regards to the TCase or the gears inside the Tcase. So, its worth a shot. If it doesn't work, then I'll just chalk it up and move on.
Thanks again for all of the help and the really good information.

Doug

 

[Kablam]

I had a similar problem and contacted SOR to see if they could help.

Found out that there is a number printed on the side of the pinion gear (sorry if I got that term wrong)... the gear that slips over the output shaft on the Tcase.

Very small and very hard to read, but it'll tell you what tooth count you need.
(i.e. 6 x 18, etc.)

I'll include a pic that I had to take through a jewelers glass.

I had a 17 tooth gear, and (as seen in the pic) I need an 18.