g741.org

I can't seem to find a replacement. It's part L, here under "Transfer case and hand brake linkage":

http://www.surplusjeep.com/M37/group_8_transfer.htm

It's just an o-ring, so does anyone know what size it is?

thanks

Hi Chris,

My copy of the ORD is a little messed up on that part number, as some of the dimensions are hard to read or not fully printed. I think it's saying the dimensions are 11/32 ID by 27/64 OD by 0.140 thick. It says it's a Seal, Oil, Type ML, but I can't find the decoder ring for old seal designations. In my ORD is listed at the bottom of page 219 as part number 741'1663, an obvious typo, but as stock number G502-7411863. This is in section Group 8 Transfer, subsection 0809.2. There's another seal listed underneath it, much bigger, for the companion flange, so I'm not sure what they are trying to say.

I hope that helps.........if not let me know and I can dig deeper.

thanks,
bob

Thanks Bob, but I think that one of those numbers must be off as 11/32 ID by 27/64 OD should result in a thickness of .040. I think I'll just go to a shop and see if I can find an O-ring that fits into the end of the pinion nut.

On the other hand, it might be better to just not install a seal, because with the pinion gear shaft spinning inside the pinion nut it looks like it would be better of some lubricant got up in there.

Chris P wrote:Thanks Bob, but I think that one of those numbers must be off as 11/32 ID by 27/64 OD should result in a thickness of .040. I think I'll just go to a shop and see if I can find an O-ring that fits into the end of the pinion nut.

On the other hand, it might be better to just not install a seal, because with the pinion gear shaft spinning inside the pinion nut it looks like it would be better of some lubricant got up in there.

Allowing the transfer case oil and the speedo drive cable grease to mix might not be a good idea.

Chris,

Sorry about that, the numerators for the ID and OD aren't readable in the ORD so I took a guess at what was left.

If it's an O-ring and you know the thickness (0.140), then just measure the OD of the shaft it's going on, add to that twice the thickness (2 x 0.140) and you have the ID of the O-ring. No?

regards,
bob

Bob, that sounds right to me.

Elwood, that's a good point. That also reminds me that this is a good opportunity to put new grease on the speedo cable. What type of grease is preferred?

Thanks

Chris P wrote:Bob, that sounds right to me.

Elwood, that's a good point. That also reminds me that this is a good opportunity to put new grease on the speedo cable. What type of grease is preferred?

Thanks

I use the same grease as I use for wheel bearings: Amsoil Synthetic Multipurpose Grease NLGI No. 2.

I found an O-ring at a hardware store that seems to fit. I don't know the dimensions, but the bin that it was in was labeled "No. 8."

I'm not sure what the "No. 8" bin label means, but it doesn't sound like the right dash number, which is how O-rings are sized. I think the correct o-ring size is a dash number 110, which has dimensions of:

ID = 0.362"
OD = 0.568"
Thickness = 0.103"

I measured the speedo pinion shaft diameter on an NOS shaft to be 0.370", which would allow for an 0.008" interference fit at the oil/grease sealing point between the shaft and the o-ring. The grooved counterbore of the pinion "nut", which holds the OD of the o-ring and keeps it from spinning with the pinion shaft, measured at apx. 0.565", allowing for a slight interference fit of the OD.

This Viton fluoroelastomer one from McMaster-Carr should work: 8297T169. It's probably a better choice for this application than a plain Buna-R one because of the contact with the spinning pinion shaft.

From the McMaster website:

"These O-rings stand up to wear caused by moving parts, such as in cylinders. Inch O-rings are sized to the SAE standard AS568. Chemical-Resistant Viton® Fluoroelastomer—Offering the same excellent chemical resistance as multipurpose Viton® fluoroelastomer O-rings, except with a durometer of A90 (hard) for better wear resistance. These resist boric acid, citric acid, isopropyl alcohol, fuels, and transmission fluids. They meet ASTM D2000/SAE J200. Temp. range is -20° to 400° F. Color is black."

Ah ha!......I was close. With that little bit of help from Elwood I can see the ORD was trying to say 11/32 ID by 37/64 OD with a thickness of 0.140 in. Now the Type designation "ML" must be old lingo because I can't find anything online that explains it........and that's a bit odd as even old standards and designations are documented for posterity. But I'll keep looking.

Good info in this thread, I'll add it to my notebook.

thanks guys,
bob

Bob, the difference in the thicknesses of the spec (0.140") and the o-ring I suggested (0.103") makes me think that the p/n I suggested might not have enough thickness to seal properly. A dash 204 o-ring might work:

OD = 0.637"
ID = 0.359"
Thickness = 0.139"

I'm going to order a package of each type and see how they fit with the NOS pinion shaft and pinion nut that I have.

I haven't found an explanation of the type "ML" seal, either, but this Timken catalog explains more about seal design than most of us will ever want to know.

http://www.timken.com/en-us/products/se ... s/7707.pdf

Many thanks!

Elwood,

Yeah, who thought there was so much to know about O-rings?? I was looking at the Parker catalog and in the codes section it mentioned that "M" was for Military and "L" was for the type of elastomeric material.......but the order was wrong........it should have read "LM", not "ML". So I'm not sure what's up. But let us know how you make out with the two O-rings. That's one of those things we'll need to know one day and it would be nice not to have to do all this digging all over again.

Thanks,
bob

Will do, Bob. I should have them by the end of next week.

Good find in the Parker catalog. Makes sense that the "ML" is somehow military. I haven't found a reference to it in any civilian application.

Since I have a collection of spare speedo pinion retaining nuts, I've been thinking about drilling and tapping one for a zerk fitting as an experiment. There's no convenient way to lube the speedo cable, especially the lower end, and since there are metal-to-metal contact points between the speedo pinion shaft and the inside of the nut, adding a zerk might be a good thing.

Bob, I received the o-rings and test fitted them in an NOS pinion nut and pinion shaft combination.

The 204 size o-rings are definitely too large on the OD to fit in the counterbore of the nut.

The 110 size o-rings appear to be the correct size, both OD and ID. They have a slight interference fit around the pinion shaft, but with some lubricant from the speedo cable grease and the abrasion resistance of the Viton fluoroelastomer material, these should function to keep the transfer case oil and the speedo cable grease separated without being torn up in short order.