Ring Gear and Differential M38A1

Bob_C · Posted: Sat Jun 14, 2014 2:34 pm Post subject: Ring Gear and Differential M38A1

Hi all,

I haven't posted in a while with any kind of regularity. I've been checking in from time to time though.

Anyway, I have a question for any folks that have done this before. I restored my m38a1 a few years ago now. Long story short, I noticed small metal flakes in my rear differential oil. Pulled the cover off, and noticed right away that the ring gear is quite pitted from corrosion. I'm thinking this is from years ago (before I owned it). The previous owner replaced the original differential unit with a trutrack positraction (brand new) unit, and I don't think I spent much time in the rear differential because of it / didn't notice it.

So, my immediate problem is I need a new ring gear. I also am leaning towards popping open the trutrack unit to inspect it now, as I have found out that the posi doesn't seem to engage. If I stick with the trutrack, I may need parts...and to tell you the truth, I don't even know if they are still in business. Like I said, the few times I've needed it to engage, it hasn't, and so I'm leaning towards ripping it out and putting the original one back in. However, my original differential, of which the ring gear came off of, is also pitted in similar fashion. If I go this route, I'll need a whole new unit. I'll also need the original spindles, as the trutrack makes use of different spindles ( similar to ones that are in the front.) I'll also need the original axles (trutrack has a different spline).

The laundry list is getting long, as you can see. Thus, I am thinking of using the trutrack still. Does anyone else have any experience with these units? Is it worth keeping? Curious as to why the posi didn't engage. Like I said, this was installed years ago by the previous owner...not sure if it a matter of some adjustment being missed, etc

Anyone have a favorite source for ring gears? I rebuilt my transmission and ordered parts from Novak a few years ago, but I'm not sure if he deals in this sort of thing too.
_________________
Bob Collins
1954 M38A1 MD79056

wesk · Posted: Sat Jun 14, 2014 3:58 pm Post subject:

I'd go straight to the horses mouth:
http://www.drivetrain.com/parts_catalog/positraction/true_trac_detroit_positraction.html

dago_red

wesk · Posted: Sat Jun 14, 2014 10:57 pm Post subject:

The truetrac would have come in a 30 spline configuration and loopback mentions the odd spline count and free floaters in his original post.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

Bob_C · Posted: Sun Jun 15, 2014 7:56 am Post subject:

Correct, they are floaters with the Dana 25 spindles. And yup, they are thirty count axles. I thought it was a neat mod at the time, and thus didn't change it.

Thanks for the link Wes. I don't know why I didn't see this originally. I guess I wasn't looking at eaton. The original paperwork I have on it from thirty years ago lists it as a Detroit trutrack I think.

As I said earlier, I found fine metal in the oil, I suspect mostly from the pitted ring gear. I'm not sure yet if this has damaged the trutrack itself in any way. Looked at the prices for a new one, and they look steep. I had the m38a1 out at a small airport out here during the winter driving on the taxiways before they plowed the snow, and the trutrack didn't seem to be working very well. I'd often get into situations where one wheel was spinning.....just driving on a flat snowy surface.

In any case, I guess I should price out the original configuration. I have some spare parts that were given to me, but I've found in the past many of these parts are well used and abused.
_________________
Bob Collins
1954 M38A1 MD79056

wesk · Posted: Sun Jun 15, 2014 10:42 am Post subject:

Don't overlook my comment on the correct oil. If you are currently using synthetic 90-140 GL3, 4 or 5 oil then that's part your problem.

Eaton still labels your diff an Eaton Detroit TruTrac.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

Bob_C · Posted: Sun Jun 15, 2014 1:38 pm Post subject:

Thanks. And I'm aware of the oil recommendation, it's on my old documentation too. Not using synthetic anything in the jeep. Pulling it apart later today.
_________________
Bob Collins
1954 M38A1 MD79056

dago_red · Posted: Mon Jun 16, 2014 10:15 pm Post subject:

wesk · Posted: Tue Jun 17, 2014 6:46 am Post subject:

That is what he realizes. He will basically need a complete A1 44.

And yes he mentioned the floater by this reference to spindles which should have read hubs in his first post:

Bob_C · Posted: Thu Jun 19, 2014 7:18 am Post subject:

Hi all,

Sorry for the confusion with some of my terms. I was typing the original posts on an iPad, and I tend to get a little sloppy on it. My apologies.

I think I have the axles and appropriate hubs from a spare rear end I have. I took the spare apart to see if I could use the differential itself, and it is in rough shape (corrosion). The axles at first glance look fine, and the hubs just need a little bit of sand blasting.

I have two differential cases with pinion gears for the D44. On both sets, the pinions look rough. Anyone have a favorite source for rebuild kits for these?
_________________
Bob Collins
1954 M38A1 MD79056


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