Anyone know Speedo gear specs? - PeachParts Mercedes-Benz Forum

Junkman · #1 09-09-2010, 11:40 AM

The odometer in my 85SD hasn't worked for a while. Prices are all over the place for having the cluster worked on. Most places apparently only repair what is broken now which I don't consider to be a "rebuild".

One place offered the plastic gears at $20 each + shipping. (Usually only 3 of 4 plastic gears go bad.) I've found sources where gears are only ~ $5.00 each but I need to know the details. Hopefully, I can find/install the gears & post the source.

vstech · #2 09-09-2010, 11:43 AM

I just rebuilt a customer's 85SD... I could go look up the specs, but I think it was an 18tooth with the standard 40's

rpansing · #3 09-09-2010, 02:34 PM

The odometer in my 85 SD was not working when I purchased it a few months ago. I purchased replacement gears from odometergears.com and replaced them myself. It is a fairly easy repair and the instructions they supply are very clear. The parts are not cheap, but they sure look more robust than the failed pieces.

Biodiesel300TD · #4 09-09-2010, 03:06 PM

I second odometergears.com. I fixed an SD odometer with the gears from there. It was a 10min fix.

Junkman · #5 09-09-2010, 08:02 PM

Quote:

Originally Posted by rpansing

The odometer in my 85 SD was not working when I purchased it a few months ago. I purchased replacement gears from odometergears.com and replaced them myself. It is a fairly easy repair and the instructions they supply are very clear. The parts are not cheap, but they sure look more robust than the failed pieces.

That's nice. Easy and cheap would be preferable to easy only. The $20 gear price is because of knowing the specs, not any inherent value. Actual retail price is somewhere between $3 & $5.

Since posting, I've taken my speedo apart and the black gears and the top white gears are crumbling. There appears to have been another small black gear on a 3rd shaft that is completely gone.

Worse than paying $80 including shipping for a few pieces of round plastic would be to pay and find something else is needed.

The gear thickness appears to be 2.5mm. The shafts are 2mm. From what's left, I can't tell even close what gears mesh. It looks like there are teeth on the bottom of the top black gear that mesh with the top of the bottom double white gear. That would leave the top black gear to mesh with whatever goes on the 3rd shaft.

I've found several sources for metric gears but need number of teeth and diameter of the gears. I may get to a yard tomorrow & will report bck if I find anything interesting.

Sev · #6 09-09-2010, 10:32 PM

dieselgiant has a good odometer repair link which i used to repair my w123 odometer. the same principles could probably be applied to the w126 if the tin gear is the culprit

Hit Man X · #7 09-09-2010, 11:27 PM

When I replaced the 'E3' gear in the the SD and 300SEL I used:

13 tooth = 2.88:1 axle
16 tooth = 3.46:1 axle

I guess a 14 tooth would work for the 3.07:1 diff and the 12 tooth for the 2.47:1 diff.

vstech · #8 09-09-2010, 11:35 PM

Quote:

Originally Posted by Sev

dieselgiant has a good odometer repair link which i used to repair my w123 odometer. the same principles could probably be applied to the w126 if the tin gear is the culprit

nope.
every gear I've had to replace in an SD has been plastic. (more of a waxy consistency actually)
TOTALLY simple compared to the 123 odometer repair.
just a few screws, and the gears are in your hand. cut off the hub of the tiny drive gear, pull the other two off with your fingers, and put the new ones on.
simple simple simple

rpansing · #9 09-10-2010, 05:42 PM

Quote:

Originally Posted by Junkman

That's nice. Easy and cheap would be preferable to easy only. The $20 gear price is because of knowing the specs, not any inherent value. Actual retail price is somewhere between $3 & $5.

Since posting, I've taken my speedo apart and the black gears and the top white gears are crumbling. There appears to have been another small black gear on a 3rd shaft that is completely gone.

Worse than paying $80 including shipping for a few pieces of round plastic would be to pay and find something else is needed.

The gear thickness appears to be 2.5mm. The shafts are 2mm. From what's left, I can't tell even close what gears mesh. It looks like there are teeth on the bottom of the top black gear that mesh with the top of the bottom double white gear. That would leave the top black gear to mesh with whatever goes on the 3rd shaft.

I've found several sources for metric gears but need number of teeth and diameter of the gears. I may get to a yard tomorrow & will report bck if I find anything interesting.

I had the exact same problem with my 85 SD. The gears appeared waxy and just crumbled when I took the odometer apart. The main drive gear, the smallest of the gears, was just a knub of plastic on the metal shaft. This waxiness is an inherent problem with the odometer gears. You might find a good set at the junkyard, but my guess is that whatever you find will have similar issues. I live in deep south Texas, so I'm sure the heat doesn't help this problem, but I looked at several cars in a junkyard and they were all as bad, or worse, than the gears in my car. IMHO it would be worth it to get the gears from odometergears.com. The gears are a different material and they sell them in a matched set. Give them a call - I found them to be very knowledgeable and very helpful.

ImBroke · #10 09-10-2010, 09:12 PM

I would have to third odometergears.com I like Jeff, and he knows the odometers.

Sev, these are totally different than a 123.

4thesporty · #11 09-10-2010, 10:10 PM

I have to fourth odometergears.com. I replaced the gears in my 85 about a month ago, very simple. I even used a dremel to add the 400 miles I lost while waiting for them to come in!