Munci Speedo Gear

[Jim K.]

I had 3.70 gears in my 61 with a munci and 27" diam. tires, it registered miles and MPH almost perfectly. I just changed to 3.36 gears and I think I'm about 10% off (onthe low side). Is there away to figure the right speedo gear to make it more accurate, and where do I get one?
Thanks!!!
Jim

[Tom S.]

Re: Munci Speedo Gear

Jim
Go to angelfire.com. I think Mike cobine run's this web site. It work's great, just put in the info asked for and it will tell you what you need to know. Tom

[Jeff Broughton]

Re: Munci Speedo Gear

There are a bunch of gear calculators out on the net. Try a search for 'speedometer gear calculator'. They generally ask for the number of teeth on the drive gear, tire size, and rear-end ratio. I can't remember how many teeth on the drive gear in a Muncie - 8 maybe?

Once you figure out how many teeth you need, you can get the gears from Chevy, or Napa has them too.

Hope that helps!
Jeff

[mike mccagh]

Re: Munci Speedo Gear

chevy dealer ought to have the driven gear you need. ju8st tell them its a muncie and that your rear axle ratio is 3.36:1. good luck, mike

[Jim K.]

Re: Munci Speedo Gear

Thanks Mike!(Jeff and Tom too!!!). I had a little trouble on the link, but if a good Chevy dealer can help, that works. Thanks again!

[Joe L.]

Re: Munci Speedo Gear

Jim-----

This could be simple or it could be complicated. It all depends upon what gears that you have in there now. That's because not all DRIVE gears are compatible with all DRIVEN gears.

Here's what happens if things are simple:

if you pull out a 22 tooth SILVER driven gear OR any gear with 21 or less teeth, all you need to do is replace it with a 20 tooth BLUE gear or a 19 tooth NATURAL gear (it's hard to say which will give the best calibration);

Here's what happens if things are complicated:

if you pull out a 22 tooth GREEN DRIVEN gear or any gear with 23 or more teeth, then you will have to do one of two things to get things right with the 3.36:1 rear gears and your current tires:

1) remove the transmission and partially diassemble it in order to replace the speedometer DRIVE gear. Depending upon which Muncie that you have you will need a speedometer DRIVE gear of GM #3708145 (63-67 Muncie)or GM #6261795 (68-70 Muncie). Both of these are GM-discontinued, but available in aftermarket cross-referenced from these numbers. After replacing the DRIVE gear, you can install either the 20 tooth BLUE or the 19 tooth NATURAL DRIVEN gears;

OR

2) install a speedometer adapter precision-geared to modify the output speed of your current speedo gear set-up to compensate for the changed rear drive ratio. You can do this yourself with "off-the-shelf" adapters, but it may also require a change in the DRIVEN gear to work with available ratio adapters. Otherwise, a speedometer shop can set-up an adapter for you.