Speedometer error with different final drive

[Tony H]

I installed a 3.27 axle in my 111 and as a result the speedo reads low-as I knew it would. Is there a different drive gear that will fit my trans to give me the correct speed? My friend thinks the different gears are offset to compensate for the different diameters. I don't want to modify my speedo.
Tony

[Tomguy]

From what I understand of other people who have done this, popping the 4.5 gear into the speedo drive should be an easy fix and do the trick.

[GGR]

Originally Posted by Tomguy

From what I understand of other people who have done this, popping the 4.5 gear into the speedo drive should be an easy fix and do the trick.

Do you mean changing the gear on the trans end side or replacing the speedo internals? I will be in the same situation soon as I'm planning to replace the rear end. As far as I understand, all drive gears are the same on the trans end side. i have a 4.5 speedo and am still to see if the internals can be swapped with the 3.5 Coupe one.

[kraakevik]

If you're running newer low-profile tires or rims on the rear much of the necessary correction may be baked in--the original tires were much taller.

Tim Kraakevik
kraakevik@voyager.net
Four M110's

[Tony H]

I am hopefully talking about changing the trans end gear on the speedometer cable. I don't want to buy parts just to see if it works so hopefully someone has some expierience with this. I am not going to modify my speedometer so if the gear does not work I will live with it(when I get it back on the road)

[GGR]

Originally Posted by Tony H

I am hopefully talking about changing the trans end gear on the speedometer cable. I don't want to buy parts just to see if it works so hopefully someone has some expierience with this. I am not going to modify my speedometer so if the gear does not work I will live with it(when I get it back on the road)

I looked into this some time ago and IIRC the trans end gears are the same and speedo calibration are different. EPC gives different p/n for speedos with different diff ratios. I will let you know if the 4.5 internals fit into a 3.5 speedo when I reach there.

[Tomguy]

I am talking about the trans end gear. A mechanic several years ago told me they are different. I would hope he was right, but I can't promise that!

[Tony H]

No biggie-I will come across the parts to try in my travels. As far as the speedo goes-i would be interested to see if that works. Keep us posted.

[Tony H]

I read on another forum that all MB speedometer drives use the same ratio and the correction is made in the speedometer-which means changing gears is not a solution. But I found this on the internet-seems like it might be a workable solution.

http://homepage.mac.com/gwellman/ratioadpter.htm

[250 Coupe]

Palo Alto Speedometer used to get good reviews, I have not seen it mentioned recently though.

Michael

[Tony H]

Thanks. I am hoping for a solution that keeps my speedo original.