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Got everything back from getting the rear rebuilt and have been doing paint work on areas of the undercarriage i wouldn’t normally be able to reach along with fiberglass repair to the battery box .
My car had the 3.08 HD posi. While it was a great highway gear it was tough in beach traffic where I felt like I was riding the clutch a bit much. Not certain which Muncie trans it has but its a good bet it’s the M20 wide ratio which was paired with the 3.08 and 3.36 gears. I didn’t want to give up the highway cruise capability completely but I did want to step it up so I went with the 3.36 gear set with the rebuild. Tomorrow I’ll be changing the speedo gear and from what I’ve read it looks like its the 20 tooth gear thats paired with the 3.36 gear set. I also picked up a new bullet to avoid possible leaks afterward.
Anyone to confirm I’m correct on the 20 tooth gear working with 3.36 gears ?
Looking forward to getting the car back on the road while we still have some summer weather left.
I have a M20 and changed from a 3.36 to a 3.73. I'm sure I still have the original gear somewhere in the garage. If I can find it I will be happy to send it to you.
I have a M20 and changed from a 3.36 to a 3.73. I'm sure I still have the original gear somewhere in the garage. If I can find it I will be happy to send it to you.
I really appreciate that but I had purchased a selection of speedo gears and a new bullet with them.
What you can do is provide much needed info starting with what is the color of the gear you removed and it’s number of teeth ?
What color gear and tooth count did you change to for the 3.73 ?
You wouldn’t happen to know the color of the drive gear on the shaft inside the trans ? Green or yellow ?
And finally what year is your Corvette ?
I appreciate whatever information you can provide. Thank you !
I checked my notes, 336 use a 20 tooth but I don't remember the color think it was blue. 373 use 22 and there were two, green I believe is the correct one.
I checked my notes, 336 use a 20 tooth but I don't remember the color think it was blue. 373 use 22 and there were two, green I believe is the correct one.
thank you Gary . I did do a google for a chart and it got more confusing. There’s a 7 tooth or an 8 tooth drive gear depending on the year so the driven gear changes depending on the drive gear for a given year. Eckler’s provides this for the blue 20 tooth gear, concurring with what you’ve said. It also shows the difference that one model year can make. More ‘68 weirdness. You’ve said 20 for the 3.36 and 22 for the 3.73 so I’d assume 21 for a 3.55 and backing up I’d also assume backing up to a 3.08 I’d expect to see a 19 or 18 tooth. I’m going to pull that out today so with what ever I find in there I’ll be going up about one tooth.
I’ll also get the inspection camera in there to take pics of the driven gear. Expect to see a green gear with 7 teeth.
Ok, got it done today and I feel comfortable now with the 20 tooth speedo gear for the 3.36 rear.
As Gary said the 3.73 calls for a 22 tooth, the 3.36 a 20 tooth (blue), stands to reason the 3.55 gear would use a 21 tooth and you’d expect the 3.08 to use a 19 tooth gear. Well mine had a 3.08 gear set and now having pulled the gear out I found it to be it natural in color and I counted 19 teeth.
Is this true for later years or even a ‘69 ? I don’t know but if you’ve got a ‘68 Vette like mine it’d roll like this …
3.08 needs the 19 tooth speedo gear
3.36 …. 20 tooth
3.55 …. 21 tooth
3.70 …. 22 tooth
I’ve seen other models, automatics where they’ve done this job and had no trouble getting to it but I had to remove the rear trans mount on the Muncie 4 speed so I could get anywhere near the speedometer cable.
Try getting a wrench or pliers on this
I used a floor jack with a board to support the trans an lifted it ever so slightly to be able to get the rear brackets out of the way.
I'm glad someone could help you. I looked through all my parts bins and could not find my old gear( found some other stuff I've been looking for).
I do greatly appreciate it though, thank you.
Might have had the rest of the car back together yesterday but my nephew was having trouble with his boat so off to that. And so it goes right ?
I get my work done between my family’s needs.
I’ll get it back in the wind soon though.
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Speedo gear change
