I'm still have speedometer problems

Deadguy · Post by **Deadguy** » Sat Oct 06, 2012 2:59 pm

I pulled the speedometer drive gear. My mechanic buddy with a lift who put in the new transfercase said the tip of the drive gear broke off, and he spent forever fishing it out. My speedometer is reading high, I think I have a NOS gauge, I have the rear 5:38 axles, so I was thinking maybe it was that sheered off tip that made the difference? I got one from John at Midwest Military. His is too short, and he doesn't have the longer one. I called my mechanic buddy, and he thinks it might be the gyro in the gauge, he says that tip shouldn't make a difference. Any opinions?

idiocrates · Post by **idiocrates** » Sat Oct 06, 2012 5:37 pm

That's sure a lot different then the one I found in the transfer case in my a1. Here's what it looked like....

P1010076 by idiocrates, on Flickr[/img]

Have you verified that the two gears that make up the speedometer drive are properly matched?

Deadguy · Post by **Deadguy** » Sat Oct 06, 2012 7:06 pm

John says I have a later style speedometer drive gear. It looks like you have the shorter version John sent me. I think the main difference, is that the longer one is to accommodate the waterproof sleeve, the thing on the far right in my hand

Post by **wesk** » Sun Oct 07, 2012 8:18 am

Let's make a few things a bit more clear.

The gears in Ed's photo are DRIVEN gears. The speedo drive gear is the fatter short gear in John's photo. The correct driven gears will have 15 teeth. The correct drive gear has 4 teeth. If you have these matched correctly and the speedo reads high with stock 5:38 rear axle and 700-16 tires then the speedo is at fault.

The early M38 used a different length driven gear, sleeve and flex cab le assembly then the later M38. The switch occurs at MC44029. The late M38 and all M38A1's used the the other lengths.

If Midwest sent you a 8328480 (WO# 806718) driven gear then you now have the correct gear. The speedo flex drive cable should be 56 3/4" long.

All of these parts are listed on pages 372 & 373 of the M38A1 ORD 9.

Deadguy · Post by **Deadguy** » Sun Oct 07, 2012 4:59 pm

Wes, I sent John the driven gear back. Let me make sure I'm going with the correct assumptions. The driven gear is 15 teeth. The one inside the transfer case (which i haven't removed) is actually 4 teeth. Is the longer shaft one I have actually not correct? Does the sheered off end tip make any difference?

Post by **wesk** » Mon Oct 08, 2012 7:40 am

The long and the short will do the same job in either jeep. The key is to match them with the correct sleeve (the threaded retainer) and the correct length flex cable.

Yes the small pilot tip is needed to keep the gear supported in proper alignment with the drive gear. Running one with a broken pilot tip will result in nasty gear wear and risk jamming of the gear which will snap the flex cable.

Measure your flex cable length. The 56 3/4" cable is late M38 & all M38A1 and is used with the long shaft SW# 448361 and the 54 1/2" cable is early M38 used with the early short shaft.

Deadguy · Post by **Deadguy** » Mon Oct 08, 2012 2:58 pm

Thanks Wes. I'm pulling it right now. I haven't driven the vehicle too much, you think it's already caused gear wear?

Post by **wesk** » Mon Oct 08, 2012 8:18 pm

Just inspect the drive gear with a a good light and the transfer in 2 high and one rear wheel off the floor so you can rotate the gear.

Deadguy · Post by **Deadguy** » Tue Oct 09, 2012 10:35 am

Is it fine to run it without that driven gear? I'll have one in like two weeks

Post by **wesk** » Tue Oct 09, 2012 9:13 pm

You'll need something in that sleeve to keep the gear oil in the transfer.