lowrider Posted July 16, 2007 Share Posted July 16, 2007 i have a unique problem. hopefuly i can get some direction from someone that owns and knows corvettes. when i first bought my car it's speedo didnt work. i just brushed it off thinking the cable wasnt connected. well today i went and checked the cable on the back of the speedometer it was attached. so i disconected the cable from the trans when i removed it it seemed to be at a radical bend. i hooked a hand drill up to it to see if it registered, with my dad watching the speedometer it worked. i then rerouted the cable so it wouldnt be in such a bind. i took it for a test drive and it still didnt register. ive come to the conclusion that i need an adapter to help eliminate the bend it has to make to get to the transmission's output. when i was searching i came across this http://www.parts123.com/parts123/yb.dll?parta~dyndetail~Z5Z5Z50000050e~Z5Z5Z5AALGZ~P39.95~~~~~~~F i got to looking and it says it fits a year model corvette from 1956-1982. my question after all of this spill is if the corvette's speedo cable is diffrent from a cable that attaches an autometer speedometer to a 350 turbo trans. any help will be appreciated. Quote Link to comment Share on other sites More sharing options...
e_racer1999 Posted July 16, 2007 Share Posted July 16, 2007 i don't remember how my old 350TH was set up, but i know on the Z trannies there is a separate gear that turns the cable. is there a replaceable gear inside the tranny that turns the cable? Quote Link to comment Share on other sites More sharing options...
lowrider Posted July 16, 2007 Author Share Posted July 16, 2007 im not sure tranies arent realy my forte Quote Link to comment Share on other sites More sharing options...
e_racer1999 Posted July 16, 2007 Share Posted July 16, 2007 looks like there are speedo gears (thought so). it more than likely needs to be replaced. i'd fix that kink, too. here's a link to speedo gear ratios/PNs: http://www.v8volvo.se/mekartips/artiklar/speedo-gear.html Quote Link to comment Share on other sites More sharing options...
lowrider Posted July 16, 2007 Author Share Posted July 16, 2007 im glad that it may just be a gear that is striped. i apreciate all of the help! Quote Link to comment Share on other sites More sharing options...
e_racer1999 Posted July 17, 2007 Share Posted July 17, 2007 no prob! good luck! Quote Link to comment Share on other sites More sharing options...
Teekass Posted July 17, 2007 Share Posted July 17, 2007 This picture is from a 700R4, but it's close enough to a TH350 to explain it. The inner part of the speedometer cable is square....you know, the part that you turned with the drill. It goes into a square piece of plastic in the transmission (where the white arrow is).....this square piece is the long end of the Driven gear (the purple thing in the picture below), and it can "round-out" inside. When this happens, it can no longer turn the speedometer cable. This is normally what happens when a speedometer cable binds, as the gear keeps spinning, but the speedometer cable doesn't turn. What I would do is replace the Housing and Driven gear assembly. It's very easy to replace. All you do is remove that one bolt you see (to the right of the speedo gear housing in top picture), remove the plate under it, and pull the housing out....might have to pry it a bit with a screwdriver. The reason I would replace the Housing also (as opposed to only replacing the gear), is they're cheap and they come with a new O-ring. I get all my speedometer stuff from these guys http://www.transmissioncenter.net/speedometer_calibration_______va.htm . The 3 items to get are: 1 - A Driven gear with the same number of teeth as whats in your transmission now. Part#68X. 2 - A new Housing (also called a Bullet). Part #66XX 3 - A new Housing Retainer. Part#68R I bet this would fix your problem. A less likely possibility is that your gears are stripped. If so, hopefully it's the Driven gear that's damaged, not the Drive gear (the Drive gear is the green one mounted on the output shaft in the top picture), because to replace it you have to remove the tail housing from the transmission....It's not that big of a deal, there are just 4 bolts holding the tail housing on, but it does require more work. Oh yeah, and while you have the tail housing off, replace the rear seal. Hopefully, this isn't your case, so when you pull out your speedometer gear housing, look inside the transmission and see if your Drive gear looks ok. If it's damaged, it will be hard to determine how many teeth are on it from just looking inside the little hole that the gear housing came out of. In that case, I would call the guys at the link above, and after answering a few questions (rear gear ratio, and tire size) they will tell you what Drive and Driven gears you need: Then buy: 1 - The 3 items from the picture above. 2 - 2 or 3 (because you might break a few figuring out how to get it on) Drive gear clips. TH350 5/16" is all it says on the web site (no part#). 3 - Drive gear. Part#68X2 Good Luck! Quote Link to comment Share on other sites More sharing options...
lowrider Posted July 18, 2007 Author Share Posted July 18, 2007 thank you for all the info. i got to poking around today. i took the retainer and gear out and the gear was striped. we have a 400th laying around in garage so i canablized it and took the gear out of it and replaced it with the one in the z. it worked but the speedo was reading 90 when i was crusing 45. then after about 4 miles the speedo died. i figure that like you said teekass that the cable is binding the gear causing it to strip. so it all comes back to my first question will the adapter in the link in my first post work with the 350th? thank you for the site, i think i may call them tommorrow to see what gear i need for my setup. Quote Link to comment Share on other sites More sharing options...
Teekass Posted July 18, 2007 Share Posted July 18, 2007 I don't know anything about the adapters.....the post I made is pretty much all I know on the subject, LOL. I'm sure the guys at Speedometer World can answer your question though. Also, if you tell them what color your stripped out gear was, I think they can tell you how many teeth it was so you can get your speedo reading correctly again. Glad I could help, even though it wasn't much. Quote Link to comment Share on other sites More sharing options...
lowrider Posted July 18, 2007 Author Share Posted July 18, 2007 i was looking on this site http://www.transmissioncenter.net/speedometer_calibration_______va.htm and they have a 90* adapter but for $88 i can go without a speedometer for a while. Quote Link to comment Share on other sites More sharing options...
Teekass Posted July 18, 2007 Share Posted July 18, 2007 i was looking on this site http://www.transmissioncenter.net/speedometer_calibration_______va.htm and they have a 90* adapter but for $88 i can go without a speedometer for a while. 88 bucks, ouch! Is there a factory application of them?....that you could find in a junk yard? Quote Link to comment Share on other sites More sharing options...
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