Speedometer Repair

[JBJeep]

My speedometer just quit working in my newly restored M38A1.
It's original and I just had a new lens case put on it, so I'd rather repair than replace.

Can anyone recommend a shop?
Preferably, someone with experience with these because of the sealed case.

Thanks

[45auto]

You can give Bob's Speedometer a try. I know a couple of people who have use them and were happy with the results. However, they are not cheap!

https://www.bobsspeedometer.com/

[RonD2]

Broken cable?

[JBJeep]

Still checking the cable, my mechanical mastermind is out of town and I'm out of my depth.
But, during the restoration the cable was checked and lubed,
So assuming the worst...

Anyone have a 8376375 or the earlier 7760396.
My G-758 manual says that will fit instrument clusters with different part numbers, I do not know if that means they would NOT work in mine.

Also, since my manual is dated 1956, it doesn't say if there are later part numbers which will work.

45Auto
I thought of Bob's due to their ads in various places.
However, I was warned to stay away from them by a MV restorer/dealer/parts source I trust.
I do not know what his opinion is based on...
I have nothing against them, but I know enough to listen to guys who know more than me.

[RonD2]

Still checking the cable, my mechanical mastermind is out of town and I'm out of my depth.

I believe I'll hold off with any troubleshooting advice until your mastermind gets back in town.

If you have to get ready to buy a speedo before knowing what the problem is, I could recommend calling several of our venerable military parts vendors:

MWM, AJP, QTM, BMJP, and several others.
I also see them on fleabay now and then.

Good luck!

[wesk]

I just had a new lens case put on it,

Which shop did the work on it? I'd be inclined to check warranty first before shopping.

There's not a lot of rocket science in these antique speedo systems. You simply 1 - disconnect the drive cable from the transfer case. Using a battery operated drill connect the drill to the end of the cable. Use the drill to speed up and down while you have someone observe the speedo. If the speedo doesn't work at all 2 - then remove the cable from the back of the speedo and spin the cable with the still attached drill a short burst and see if the top end is turning. If the top end is turning then the speedo is the issue. If the speedo works during step one then the drive gear in the transfer is the problem.

[JBJeep]

The new case was installed by a shop recommended by John at Midwest Military.
That was my first stop.
He told me the shop was closed, I suspect the guy retired.

As far as a new unit, even just to keep one as a spare,
I checked the usual military Jeep parts vendors (as mentioned by RonD2 above):, three have repros which lack the correct markings...they have the later "MS" numbers,
one has a pricey NOS (unknown markings...I am awaiting a reply on that),
one has a later NOS unit which may or may not work.
My parts manual is a reprint of the original which obviously does not list later units.

[4x4M38]

And be sure and operate the drill in reverse.

[wesk]

I didn't say which way on the drill because I have way to many different systems on my tray all the time. If any speedo check doesn't show activity in one direction the common sense thing to do is switch directions. Not a lot of choices. Only two.

JB, I noticed you said this in your original post: "It's original and I just had a new lens case put on it"

And the shop retired already!

[RonD2]

Here ya go.......NOS, last one:
https://www.ebay.com/itm/175093592720?h ... R8q-gaHIYg

[JBJeep]

RonD

Thanks, I bought it.
Not a bad price for a new correct unit (albeit an older version).

[RonD2]

You're welcome.

And in case you need it, here's a NOS cable:
https://www.ebay.com/itm/171860031535?h ... R9apqLTIYg

[wesk]

JB,

Anyone have a 8376375 or the earlier 7760396.
My G-758 manual says that will fit instrument clusters with different part numbers, I do not know if that means

This early gage is correct for M38A1's from MD10001 thru MD70114.

What is your A1's serial?



Here's the large version: http://willysmjeeps.com/v2/modules/gall ... _fig_s.jpg

As for the later parts manuals:

TM 9-2320-208-20P Organizational Parts Catalog dtd. Feb 1959
Speedo is not listed.

TM 9-2320-208-20P Organizational Parts Catalog dtd Jan 1966
The early speedo ORD# 7760396 FSN 6680-776-0396 is only one listed.

TM 9-2320-208-34P Direct Support & General Support Maint. Repair Parts dtd Jul 1966 does not list any gauges.

[JBJeep]

Wesk

Thanks.
Looking my manual I was checking the Speedo part numbers but failed to cross reference the gauge numbers a few inches above (duh!!!).

Okay, I bought the early M38A1 Speedo 7760396 as seen in the photo (in fact the eBay page where I bought that had the same photo).

Now my problem is will it fit my late A1?.
The manual says the cluster 7148835 was used up to serial 70114.
My A1 is 82551.
So, will it work?

A very reputable Jeep parts guy offered me the same unit, so he didn't have any concerns, likewise, the various repro units and the later military "MS" marked gauges do not mention a serial range for application.


Your red notes seem to indicate the later (non-luminous Speedos were used as replacements in early A1, so I should be okay.
Any thoughts?

I appreciate your patience.

[wesk]

My A1 is 82551.
So, will it work?

That makes yours about a 1957.

Yes it will fit. The various clusters differed more by their components then their own indicator cutout sizes. One obvious example of early cluster vs late cluster are the two gage light units. The late cluster uses the M151 style lamp assemblies.


The top is the Early A1 cluster and the lower is the later A1 and M170 cluster.