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Speedo gear WT hay?! |
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ccowx 
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Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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 Topic: Speedo gear WT hay?!Posted: Aug/14/2016 at 11:07am |
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I just replaced my speedo gear in an effort to get the gauge to read 100% accurately. I went to all of the online calculators etc and did what they say is supposed to work and I got the opposite effect.
Here is what I have: -T10 tranny and 4.10 gears -F70-14 tires The calculators say to use a 6 tooth drive gear and a 19 tooth driven gear. I put in a 6 tooth drive gear and a 20 tooth driven gear to at least get close while I wait for the 19 toother. Previously it read about 10% high. Now it is almost 50% too high! My logic is telling me that the more teeth are on the driven gear and less on the drive gear should slow down the speedo, not the opposite. What the heck? Thanks! Chris
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scott
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Joined: Jul/10/2007 Location: Wildwood Pa. Status: Offline Points: 3501 |
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Posted: Aug/14/2016 at 12:18pm |
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What was the original gear configuration??
If the original setup was 10% to fast, you can add 10% more teeth to the driven gear to slow it down. That works as long as there is a gear with the needed tooth count. 50% off is so far off you'll probably need to change the drive gear again. |
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ccowx
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Posted: Aug/14/2016 at 12:33pm |
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Not looking forward to taking out the tranny for the second time in a week! It was an 8 tooth drive gear and 23 tooth driven. I can't get any driven gear with more teeth, but I can't figure out why the bloody thing is suddenly up 50%! I also just tried the 23 tooth driven gear back in and it is slightly better, but not much.
It all seems to be opposite the TSM, common sense and the various calculators. Thanks! Chris
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scott
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Posted: Aug/14/2016 at 1:10pm |
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It will probably take a 7 tooth drive, & 19 or 20 driven. That's just a guess though. Put 'em in, calculate the error % & adjust the driven count accordingly.
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ccowx
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Posted: Aug/14/2016 at 3:39pm |
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According to everything I have found, the combination of 4.10 gears and F70 tires should work fine with a 6 tooth drive gear and a 19 tooth driven gear. A 7 tooth drive gear and about a 22 tooth driven should work also, though I don't have a 7 tooth gear. An 8 tooth drive gear will not work because you would need a 24 or 25 tooth driven gear and they don't make those.
I have put a 6 tooth drive gear and a 20 driven in, which should be close. Instead it has gone bananas and is reading radically out, like 50+%. I am wondering if there is some way a gear could be in wrong or something else that I don't know about that could be causing this. Not to be a smart#ss, but I am quite capable of looking up the various tooth counts that should work for myself, but something else is very wrong here and I am hoping for some insight from those with more experience than I have! Thanks! Chris
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tyrodtom
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Posted: Aug/14/2016 at 4:20pm |
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Are you sure you didn't slip up and put the 8 tooth drive gear back in ? Then your speedometer error would make sense. I've done worse. |
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66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.
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ccowx
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Posted: Aug/14/2016 at 4:38pm |
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Believe me, so have I! In this case, I had a gentleman working with me that knows transmissions, so I tackled the clutch while he did the gear. I know he put in the white one, which I believe was a 6 tooth. Are they color coded like some of the driven gears?
It is acting to me like it is somehow assembled wrong or ? Thanks! Chris
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farna
Supporter of TheAMCForum 
Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19676 |
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Posted: Aug/15/2016 at 8:45am |
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Well, you may not have to pull the entire trans, just the output housing. Not sure how easy that is with a T-10 though, since reverse is in the output housing. No help, but would be easy with a three speed...
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Frank Swygert
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ccowx
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Posted: Aug/15/2016 at 1:00pm |
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Might have found the culprit for my speedo going crazy. I was speaking with a tech guy at PATC Transmission Center in Louisiana and he told me that it could be that the drive gear is put in wrong. Apparently, it is possible for the clip to be put in several different places and if it is off center it will "flick" it with the edge of the gear, giving a false reading, usually too high.
Looks like it is off with the tail shaft housing, again, and put it in right! Thanks! Chris
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amxdreamer
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Posted: Aug/15/2016 at 2:00pm |
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I was scared to click on this post for fear of seeing Chris IN a Speedo!
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Tony
Vancouver, BC 1970 AMX 1972 Badassador AMO#10333 |
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