1G Transfer case rebuild

[dwb]

I'm about to undergo a transfer case rebuild (1g/5 speed). My drive gear splines are wore out and it's got over a quarter million miles on it. Nothing broken that I'm aware of. So a new (used) drive gear, all four taper bearings, seals (incl. the two large o-rings) and a new nut will go into it. The upper cover gasket is unavailable, so hoping RTV with do the trick there. I'm also installing a new output shaft in the transmission. Am I missing anything? Can I reuse the collar on the t-case output shaft, which looks like it sits between the two bearings?

I rebuilt the transmission myself so I'm not too afraid of the transfer case, but the one thing that intimidates me is that large nut and the taper bearings underneath it. Does anyone have any tips for cracking that nut loose? What size is it (55mm?)? I don't yet have a wrench or anything large enough and I don't have a vice sturdy enough to hold the shaft. I was thinking I'd get a large adjustable open-end wrench for the nut and use an old yolk with a bar stuck through it to hold the shaft via the output splines.

As far as the taper bearings, I'm going to attempt to use a large 2-arm gear puller/bearing separator to pull the bearings off (I have no access to a press). My concern here is the bearings on the output shaft are too far down the shaft to reach with the puller. I'm thinking I could use some sort of arm extension, either fabricate something out of steel or maybe even use my spring compressors as an extension. Not sure how I'm getting the new ones on yet, maybe just a piece of steel pipe and a hammer or maybe pull them on from the gear side with the puller.

Any comments/suggestions before I tear it apart?

 

[twicks69]

You will need a bearing splitter and press, no way around it on the inner pinion shaft bearing. The only splitter you need is an OTC1123 to do all 4 bearings with a press.

For install, well in a pinch I guess you could use steel pipe.
The inner pinion bearing is ~1.78" ID / 2.02"OD on the inner race. You would need the tube to be 12" long to clear the tail shaft and fully press the bearing on. The bearing used is a 32009X.

The outer pinion bearing is 1.57" ID / 2.14" OD on the inner race underside. You would need the tube to be 8" long to clear the tail shaft and fully press the bearing on. The bearing used is a 32008X.

I use Miller 998805 for pressing on both of the bearings. It is 1.78" ID, 2.13" OD, 12" long.

For the input sleeve bearings, the inner sleeve bearing is 1.25" ID / 1.54" OD. I just use a 1.5" exhaust pipe adapter that is 1.38" ID / 1.5" OD for installation. The bearing used is a LM67048/LM67010

The outer sleeve bearing (towards the side cover) is 1.97" ID / 2.24" OD. I use Miller 9761-3 for the outer sleeve bearing onto the drive gear, 2.031" ID, 2.25" OD. The bearing used is a 32010X.

There are two versions of end shaft nuts, early style 1989-1991.5 and late style 1991.6-1999. Early style uses a 55mm crow foot, late style uses a 50mm crow foot. You can unstake the shaft nut with a straight blade 3/16" flat head screwdriver and hammer. Sometimes they have little to no torque on them because Mitsu was lazy and didn't feel like changing out the pinion preload shim to get the proper turning torque with the torque spec for the shaft nut so they would just get it tightened to feel, then stake the shaft nut. Other times they are ridiculously overtightened and required a 24" breaker bar with a 4ft extension in a bench vise with metal soft jaws.

I use Miller MB991013 crowfoot for the early style, and then either Miller 8478 or OTC MD998834-01 for the late style. These are factory service tools.

 

[dwb]

That's a great deal of information, thanks Tim! You also hooked me up with the used drive gear last week and I appreciate your support. That was not an easy part to find.

Must be nice to have all the factory service tools. Unfortunately I don't have any of them but I'm a master at making the wrong tool work. I do have that bearing splitter, however. I'll have to check out my local rental shop to see if they have the 50mm crows foot. I didn't think about it until now, but I have access to a 25 ton press at work, so that will make things a little easier.

 

[twicks69]

Otherwise if you have access to a laser or plasma table just make your own tool.

 

[ty1975]

Literally just did this and happy to give pointers. I can post a link maybe to my thread on it if I can figure it out or if you just search transfer case rebuild questions you’ll find it.
-yes rtv works fine on the top cover
-reusing that steel collar is fine, I noticed no compression on it.
-go get a 16” pipe wrench or bigger from harbor freight to break that nut off. Just make sure you get your preload right on that nut. It will destroy your new bearings In short order if you don’t.
Biggest thing is get your preloads right. If you haven’t ordered parts yet I listed in my thread all the part numbers you can get from autozone. I know they’re all Chinese made but what isn’t anymore? Finding oem is getting tough.
Magnus has bearing shims but I was just informed they don’t have the gear depth shim that goes on the outside of the case to set your gear tooth contact pattern.
On that note make sure to get contact pattern compound and check your gear pattern. If it’s off it will make a fish awful obnoxious noise.
Go search my thread, feel free to ask questions. Oh and the only thing I had to have a press for was getting that collar off. It was seized. I cut all the bearings off. Oddly enough I didn’t even use it to get any bearing back on, I stuck parts in the freezer or oven and they slid right on. Hopefully that helps.

 

[dwb]

Finally got my transfer case rebuilt. I didn't even need a press. I got the bearings done with just a 2-arm gear puller, bearing separator, hammer, blocks of wood, and some old bearing races. Bought a large adjustable open end wrench for the big nut and used an old yoke with a bar through it to hold the shaft. Was easier than I thought it was going to be.

I had one incorrect part - the o-ring on the drive shaft cover. My version of the Mitsubishi ASA (CAPS 35) for 1g shows this o-ring as the same part number as the o-ring in the case (MF520414). Turned out the cover o-ring is smaller, so I'll be hunting down that o-ring in the near future. Can anyone tell me if MD727944 is the correct PN for a 1991.5+ cover o-ring (that's the 2g PN)?

 

[twicks69]

That is the cover o-ring, MD727944. I have them in stock also. Same with the other rebuild parts.

 

[dwb]

That is the cover o-ring, MD727944. I have them in stock also. Same with the other rebuild parts.

Thanks Tim. I also noticed my speedometer gear o-ring (MF520016) is leaking. Do you stock that part as well?

 

[twicks69]

That I do not have around. I would have to order that from Mitsu.