727 Trans Speedometer Gear

[Mr. Belvedere II]

So here I am again with another problem that has beleaguered me since my tranny swap. The transmission was like the only thing I had a shop install for me, and even then I had to adjust kickdown and all that good stuff on my own. So one of the things I noticed straight away was that my speedometer no longer worked. I purchased a 727 torqueflight from TCI knows as a Sizzler. It's been terrific and I love it the most but for some reason my old speedo gear doesn't work. So why? What I gotta do to get my speedo working again??

 

[oldbee]

Well first unhook cable from trans & spin it, does the speedo try to move? If yes then is the speedo cable adapter at trans 'clocked' at right setting for the teeth on speedo drive gear?

 

[Mr. Belvedere II]

I know the speedo works at the dash connection and that the cable will spin freely while it is connected to the trans in the fashion that it is. So I know that if it were to be set up correctly in the trans, then my speedo would definitely function

 

[Mr. Belvedere II]

Well first unhook cable from trans & spin it, does the speedo try to move? If yes then is the speedo cable adapter at trans 'clocked' at right setting for the teeth on speedo drive gear?

I don't know about the gear or how to clock it or if the gear is the wrong one for this trans or what.

 

[oldbee]

Wait a minute, if cable is hooked to trans it won't turn unless trans is spinning in gear. Maybe you have no speedo pinion gear in trans(?)

 

[Mr. Belvedere II]

Hm I need to get into that trans and see if I have a gear there. I wasn't there for the install so of course who knows what they did or didn't do or take from my original transmission when they put the new one in. So would there be two gears? A speedo gear and a pinion?

 

[Paul_G]

The speedo gear goes in the speedo gear housing called "adapter" in the picture. The housing must be clocked according to which gear is inside of it by number of teeth within a range. You can see how the housing is somewhat eccentric.

 

[Mr. Belvedere II]

The speedo gear goes in the speedo gear housing called "adapter" in the picture. The housing must be clocked according to which gear is inside of it by number of teeth within a range. You can see how the housing is somewhat eccentric.

View attachment 407105

Ha yes I just saw this very diagram whilst searching for more info! Thanks so much!

 

[66Satellite47]

If you loosen the attaching bolt for the adapter. wiggle the addapter out of the trans, the speedo gear will come along. You need to look at a Factory Service Manual to see how many teeth you need for your rear gear & tire size.

 

[oldbee]

The speedo gear in the adapter is driven by another plastic gear on the output shaft. U shud be able to see it with a flashlight after the adapter is yanked out(has an o-ring to seal it)

 

[66Satellite47]

In all my 727's the colored plastic speedo gear that fits in the adapter is driven by the helical cut in the steel output shaft.

 

[oldbee]

66sat- ur right. Somehow I was thinking of a plastic drive gear on output shaft- GM maybe? My bad

 

[66Satellite47]

oldbee, I think your guess that there is no gear in there, an aftermarket trans won't know what it should be, so how could they supply it.

 

[Mr. Belvedere II]

So so I address

If you loosen the attaching bolt for the adapter. wiggle the addapter out of the trans, the speedo gear will come along. You need to look at a Factory Service Manual to see how many teeth you need for your rear gear & tire size.

So I addressed this issue today while I had the car on my ramps. After loosening the clamp for the and pulling out the housing (and letting loose a waterfall of trans fluid I didn't expect. Fortunately I had a buddy quickly pass me the catch basin!) I discovered my gear is a 30 tooth yellow and it's plainly marked with a 30. I looked up into the hole in the trans and saw the metal drive shaft that is for driving the gear. I put the cable into the gear and gave it a spin while my buddy watched for the needle to bounce, which it did. Then I set them all back into the hole with the housing shaft in the highest position and the corresponding numbers at the 6oclock position. I was certain that my gear would meet the drive and my speedo would work. Alas, it did not. What could I be missing???

 

[Mopars & Missiles]

Your photo of the yellow 30T gear looks like the teeth are ground down on one side. If so, it will rotate until it gets to that spot and there it will sit. No turny!

Maybe its just my optical delusion??

 

[Mr. Belvedere II]

Your photo of the yellow 30T gear looks like the teeth are ground down on one side. If so, it will rotate until it gets to that spot and there it will sit. No turny!

Maybe its just my optical delusion??

I think it just looked that way. I had a good look at it and didn't see any stripped parts

 

[oldbee]

Nope it still looks ground down at 3 o'clock in ur pic.

 

[Mr. Belvedere II]

Nope it still looks ground down at 3 o'clock in ur pic.

Sheesh you might be right but wouldn't it seat way deeper and get much more stripped than just that teeny little spot??? I am going to take it out again next weekend and have a closer look, but I would think that it would mesh much deeper in the gear, no?

 

[khryslerkid]

It could be a optical delusion

 

[Paul_G]

With the gear installed, try removing the speedo cable from the gear and turn the gear with a small screw driver. It should not turn. If that is correct try a battery drill on the speedo cable, have someone watching the dash and make sure the speedo needle moves smoothly as you increase the speed of the drill. If that is correct make sure the speedo cable is engaging the speedo gear fully, and in to the speedometer fully.