speedometer gear

[tactransman]

Unscrew the cable,turn the driveshaft and see if the gear is turning inside the adapter.

[shadango]

Thanks Terry...

I ended up pulling it apart to put it back together and found the o ring was very saggy...well, didnt think anything of it.....but when I put everything back together I cut trhe oring....

SO I visited a couple shops and finallyfound one that had the correct o-ring, in the right rubber compound, laying around....and another very experienced tranny guy to boot.

Got back home...tested the speedo, which work, and then put it together without the cable on and it was turning....so put the cable on and the rest is history.

Speedo is back!   

[tactransman]

 

[Changin Gears]

Ok....I pulled it tonight to look and I have a yellow/33......  33 x .1428= 4.7124

Do I round up (5 fewer) or down (4 fewer) ?  I am thinking of rounding up.....

I still have to check the 60 mph reading like you suggested.....just figured I would see what is in there.

Round up to 5

[shadango]

Thanks!

Gotta charge up the GPS so I can take a 60 mph run and then I will be set!

[shadango]

Alright......got her up to 60

......when the speedo reads 60, the GPS reads 72 or 73....we'll say 72.

12/72= .1666666666      so speedo reads 16.7% slow.

33 teeth in current gear....... 33x.1666= 5.4978 or 5.5 

Guess I will go with 6 fewer teeth, or a 27 tooth, right?

So it looks like I need the WHITE one.

[shadango]

Before you pull the gear to see what it is (other than wrong), try the spreadsheet at the link below (there is one for a auto or manual trans).  Plug in the numbers and see what gear you need.  Might save a step for you.

http://www.moparts.org/Tech/tech/pages/speedo.html

Now if I use the spreedsheet method, get a 28.66

The tag on my rearend is 2.76 (maybe it's wrong?)

235 60 15 tires in the back, measuring 25.25 inches tall from ground to top.

The chart say I would need a 28 tooth....actually a 27.72

At 72 indicated on the GPS I am running right about 2800 rpms which is right about what the spreadsheet says....

So I guess either 27 or 28 would work......27 might end up puuting me a little SLOWER than the speedo would indicate.....

...plus seeing as there IS no "28" listed in that list of available gears, I guess 27 it is!   

[Changin Gears]

Alright......got her up to 60 to...actually, 87 as indicated on the GPS.....this fish flies!  LOL

Anyways......when the speedo reads 60, the GPS reads 72 or 73....we'll say 72.

12/72= .1666666666      so speedo reads 16.7% slow.

33 teeth in current gear....... 33x.1666= 5.4978 or 5.5 

Guess I will go with 6 fewer teeth, or a 27 tooth, right?

So it looks like I need the WHITE one.

Math looks right.. could go with either a 27 or 28 (5.5 is right in the center).

[shadango]

SO they do have a 28? Didnt see one in that list..though I do see the listing on ebay is offering a 28.

I was only 14.28% off at 30 mph.......but went up to the 16.7 % at 60 ...

[Changin Gears]

I was only 14.28% off at 30 mph.......but went up to the 16.7 % at 60 ...

I'm surprised a 40 year mechanical speedo is that linear.  Calibrate for the speed you normally drive.

By the way the difference between what the speed show with a 27 or 28 tooth gear is about 2mph.  So you will either read 1mph fast or slow.

[shadango]

Does anyone happen to have a 27 tooth (white) gear they would sell reasonable?

The dealer wants $80!  Said it was $8 but the part number (2538927) was superceded....

[Purple73Cuda]

Shadango,
That is what I ran into. The gear was superceded and he told me $50 or so. I almost dropped on the floor. I forget what gear i bought. It was for a 3.23 rear, F70x14 tires.
Sorry I don't have a 27 gear for you. You should be able to find a used speedo gear if you are going to the Mopar Nats this coming weekend.

[Bullitt-]

Search this part # 2538928
here
https://www.mopar-wholesale.com/

[shadango]

Shadango,
That is what I ran into. The gear was superceded and he told me $50 or so. I almost dropped on the floor. I forget what gear i bought. It was for a 3.23 rear, F70x14 tires.
Sorry I don't have a 27 gear for you. You should be able to find a used speedo gear if you are going to the Mopar Nats this coming weekend.

I really wanted togo to the Nats but I have to chose whether to spend cash on another trip (went to carlisle) or spend it on the car......

[shadango]

Search this part # 2538928
here
https://www.mopar-wholesale.com/

Thanks!  The 27 tooth is coming up as $54!!!!!!  The 28 at $5.50!!!!

Now, come on...what gives there?!!?!?

To save $50 I guess I can go to the 28 if I cant find the 27 cheaper....