Speedometer Gears

[P72Ford]

This is not a question, but a warning.

DO NOT use the 23 tooth (black) speedometer gear in the AOD.

I have been messing with the transmission for my car, and was cleaning the exterior of the case, in preparation for paint. I decided I'd pull the speedometer sender/ gear, and block the hole for cleaning, etc. I didn't want the sender damaged.

When I pulled the sender, I found the black 23 tooth speedometer gear entirely mangled and trashed. There was only one or two complete teeth left.

My initial fear was not the broken gear, but rather the missing pieces.

After some googling, I found that this is quite a normal occurence for Mustang folks, and that at times the gear only lasts for a few thousand miles. The pitch is wrong, and the gear does not mesh correctly with the gear on the transmission output shaft. In addition, the teeth are quite thin...

On a hunch, I cut open the filter I removed from the transmission. I found every single missing tooth from the gear (no metal shavings, either). Quite a testament to the filter. They look kind of lame, but they apparently work quite well.

I have another black gear, but have no intentions of installing it if its going to self destruct again. Instead, I am going to put in a grey gear, and install a speed-cal. Definitely more expensive than a gear, but I do not wish to have any more foreign gear parts floating in my transmission.

Just thought I'd put this out there.

[86VickyLX]

Scott was telling me about the black gear and how it is a bad idea. Purple gear is the last gear to go with without having this problem.

[P72Ford]

Its funny, because I read on several Mustang forums where people have replaced the gear three and four times, and no one seemed that concerned about the missing gear teeth floating around in their transmissions.

Its not an acceptable solution, in my opinion.

If you go with 3.73s, 4.10s, 4.30s, or 4.56s, you should really just buy the speed cal. With the extra gas you're using, you can afford the extra little for the correction.

[Grand Marquis GT]

It seemed like a good idea at the time...

[BerniniCaCO3]

What is a speed cal.? (calibration?)
Does it read the shaft speed with a magnetic sensor, rather than a direct driven plastic gear?

[P72Ford]

It seemed like a good idea at the time...

Hey, I'm not faulting anyone.

I had bought one for use in my red car, but never got around to installing it.

I just don't want others to have the same issue.

[86VickyLX]

I thought it was just the speedometer recalibration to make the speedometer read the correct speed, but I was wondering about the electronic (pcm where applicable) would be calibrated?

[sly]

I have the white 23 tooth in my Mark. It's got a different slant on the teeth to better match up with the AOD. The black on is supposed to be for manual trans.

[88grandmarq]

I have the white 23 tooth in my Mark. It's got a different slant on the teeth to better match up with the AOD. The black on is supposed to be for manual trans.

actually, its the other way around... white gear is for manual transmissions and black gear is for automatics. However, the white gear has proven to be more durable. it will still come apart, but not nearly as quickly as the black gear.

http://www.mustangsunlimited.com/Sub...s=LMF201&grid=

[sly]

at least I think I have the white... maybe I'm confused (wouldn't be the first time).

[1987cp]

What is a speed cal.? (calibration?)
Does it read the shaft speed with a magnetic sensor, rather than a direct driven plastic gear?

I figured he was talking about a reduction box like they used on Drag Pak cars. I posted a few links somewhere around here to a place that offers new ratio adapters in a variety of ratios .... prices were in the $60 to $80 range IIRC, but sounds like it's even more of a good idea than I'd thought if the 23t speedo gear is crap.

I haven't bothered yet to calculate what RARs the 21t Ford piece is likely to be good with ....