speedometer turns backwards

[Canoe]

i have a 1942 Ford GPW. Is there a fitting I can install to get my cable turning the right way? I have two speedometers that both run in reverse only!

[LarrBeard]

i have a 1942 Ford GPW. Is there a fitting I can install to get my cable turning the right way? I have two speedometers that both run in reverse only!

If I remember correctly. the speedometers on the GPW/MB run off of a gear in the transfer case.

The gear turns the cable and that runs the speedometer. If the speedometer only indicates properly in reverse, it seems the cable is turning in the wrong direction.

Why that gear is running backwards is a new one to me. There may be a transfer case issue here causing the driving gear to turn the wrong way. Could someone have rebuilt the transfer case incorrectly?

[LarrBeard]

Could someone have rebuilt the transfer case incorrectly?

Funny how many of us end up working on the same area of our Jeeps at the same time. I'm a day away from replacing the speedometer cable assembly on the '48 and I'm looking at drive gears, counting teeth, etc. All the reference books say the '48 2WD with 5.38 Timken rear end should have a 15-tooth driven gear - and that's what I have. We'll see if things work some time tomorrow morning.

But, I went looking at things. Here is what I believe should be your driven gear:

https://www.vintagejeeps.com/p-686-speedometer-drive-gear-a1511.aspx

I'm going to ask what is probably a silly question - but I've asked those before. Could the gear be installed backwards - making the "threads" on the gear go the wrong way? Sillier things have happened .... .

[gmwillys]

That would be the only logical explanation. I was thinking the gear only went on one way, but like LarrBeard said, stranger things have been known to happen.

[bmorgil]

I vote "gear in backwards".

[LarrBeard]

Here is more than just about anyone would want to know about MB and GPW gauges:

http://jeepdraw.com/correctgauges.html

And another place to look for info:

http://www.fourwheeler.com/how-to/transmission-drivetrain/154-0710-control-speedometer-readings/photo-03.html

It looks like we are dealing with the drive gear vs. the driven gear. The picture of the drive gear shows a red line on one face of the drive gear. Could this be an index mark? It looks like getting to it is a bit of a task.

You might call Mike and have his transfer case guru get in on this conversation.

I looked at a Dana 18 tear down video and about 17 minutes into it the guy pulled the drive gear out of the case. There is a sleeve/shoulder side and a flat side to the drive gear. The sleeve/shoulder is the back side, the flat side is the outside. It looks like the gear could be installed backwards.

https://walcks4wd.com/speedometer-drive-driven-gear-mb-gpw.html

[bmorgil]

I don't know if your in a hurry but, I am going through my transfer case in a few weeks. Just finishing the motor now. Trans and transfer case will be next. It only takes me a few hours to go through the trans and, the transfer case is also a fairly quick build. I just need to get started! I can have some detailed pics for you if you can wait.

[bmorgil]

To get to it you have to remove the E-brake completely. Then its the bearing cap. The gear will go on either way. I put it on backwards and put the cap back on. It still engages the driven gear and turns it. As I gazed at it however I have to wonder. Either way it is still cut the same direction. The driven gear will still turn the same way will it not?

[LarrBeard]

Well, I admit it looks like it would....

Could there be an incorrect driven gear involved in this puzzle?

[gmwillys]

Ponderous. The drive gear should only difference by the amount of teeth the gear has.

[bmorgil]

OK my brother worked at The Dana Spicer Plant cutting gears in the 70's. He remembers making sevice parts for the model 18. He also remembered the purchasing dept buying all speedo gears from Detroit Gear. He remembers that there were gears cut for reverse rotation. We are not sure what for. In any event, I believe the speedo gear needs to turn clockwise for the speedo in the jeep to read correctly. The gear needs to be cut left to right, and installed with the shoulder in.

Are you still working on this canoe?

[LarrBeard]

Dana Spicer in Ft. Wayne? Out on the west end of State Street?

[bmorgil]

State street was the axle plant. We built the Transmissions and Transfer cases in Toledo at Bennett road.

[okiemark]

You could just back everywhere you go. Boy I am smart this morning.

[pelago]

i have a 1942 Ford GPW. Is there a fitting I can install to get my cable turning the right way? I have two speedometers that both run in reverse only!

just got to ssay... drive it while holding a mirror will be right in the mirror, i know smart *** right..... sure would love to hear how you solved it, was it the gear on the end of the plug reversed, that is all it could have been