Front diff ring gear to front output shaft interference

[markmakeitso]

Hi all,
I'm trying to wrap up a budget repair on my W5M33 trans, my center differential grenaded and took out the front output shaft. Finally getting close to having everything I need together to bolt up.

My current issue is that the front differential ring gear seems to be interfering with the front output shaft. With the bellhousing side down and the center diff assembly and output shaft set in their lower races spinning the teeth sound fine in the forward direction. Spinning in reverse however the leading lower edge of the ring gear seems to "clack" against the inner race of the lower bearing on the output shaft. Thinking that maybe the bearings needed the support of upper bearings the I tried to join the bellhousing and 2nd layer of the case, but that causes trouble too. The front output shaft splines are definitely just off-center of the double tapered race opening and resist moving to the center. The cases will close to about 3/16" gap and then the front output shaft starts to bind up. Obviously didn't force it together any more than that.

-Symptom appears with 2 different matched pairs of lower race/bearings installed on replacement front output shaft. I could replace with a new bearing/race, but seems like that would only increase the interference between teeth/inner race. Lower bearing is fully pressed on flush to the teeth.
-Front differential assembly looks fine, and ball bearings appear to be in good shape
-The 2 front output shafts appear to be identical (well, besides the old one being broken off at the splines). Haven't read anything indicating differences there either. Donor trans was a 93 I believe, my car is a 91 but had a replacement trans of unknown year installed previously.

Any suggestions to try? Have considered putting a shim under the front differential rather than on top to be honest. Seems like that would slightly change the speedo engagement point, but probably not significantly. No, there's no shim under the front output shaft lower bearing race to raise it up relative to the ring gear.

Thanks,
Mark

Mild update:
Found this link around the Tubes in my search for answers:
2G a/b AWD drivetrain differences [Archive] - DSM Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum: DSMtalk.com


Per the ubiquitous JackM:

"If you are talking about the output gear that meshes with the front diff ring gear in the trans then no, they are not the same. The helix angle was different on some of the 1G units. They look to have the same tooth count and mesh correctly with the naked eye, but they don't."

My guess is that's the problem I'm having. I tried it with the shim on the bottom center diff bearing side (driver's side). The clacking was noticeably reduced, although not eliminated. The next layer trans case still wouldn't mate to the bell housing however. Can I snag the the ring gear from the same trans that donated the front output shaft and run with that?

Edit: 95% sure this incompatible front output shaft is the problem. Even side by side they look identical, until you carefully inspect the angle of the helical cut. My new one is cut a little bit more steeply. It also has a slightly thinner edge on the tips of each tooth than my destroyed one. What a hassle, have been playing with this problem for several days.

 

[JackM]

I would check to be 100% sure that your lower bearing race on the bell-housing side is pressed all the way down. Sometimes there could be debris or a tight fit that would prevent it from seating all of the way without some help.

What you can try to verify that you have mismatched gears is to install the output gear and front diff. Press and hold the upper bearing on the output shaft. Turn the ring gear so that it also turns the output gear. Do you feel a vibration? It should be completely smooth.

If you do, let me know. I have 2 large totes full of ring gears and I'm sure I have one that will match. I may need you to send your ring gear, output gear, or both to find the right match. I have so many of every kind that if you pay for shipping I can match it for you. I'll just trade you the correct part for your incorrect one.

Disclaimer:
Please, pretty please with sugar on top, don't call me 15 times in a row with no message while I'm on the other line and panic with a stupid thread asking if we are open. I can't hang up on the guy with the $100,000 car needing $10,000 worth of trans work for something like this. A simple phone, EMAIL or PM message will work just fine and I would be more than happy to help you solve this issue in a quick and timely fashion. I can't believe I have to say things like this on Tuners, but it appears I have to...

Good luck!

Jack

 

[markmakeitso]

Hi Jack, thanks for the info, both recent and 4 years ago.
It does seem to mesh okay, but even spinning by hand I feel a little vibration. Would be terrible with load and more RPMs I'm sure.

I have a parts transmission an hour away, that's where the front output shaft came from. Will likely just grab that ring gear and swap to my diff. Those are all compatible hopefully. Thanks for your offer though.

 

[JackM]

Make sure the tooth count of the ring gear matches your car and original gear. It should be 58 teeth on the ring gear. The 97+ units had 57 and that's enough to ruin many parts in the center diff. If your donor trans is a1 g then swapping the gears as a set should solve all of the problems. To this day the very small changes in the output and ring gears willsometimes bite us too. Sometimes you never know if they will make noise until you spin the unit up and listen to it. I had to make an adapter for a high speed drill I have so I could listen to it without assembling the whole unit. It's amazing how many times I thought the set matched when it didn't. Mitsubishi were real slimeballs with the small changes they made to many parts in 1g units.

 

[markmakeitso]

Hi Jack,
Similar question: I tried bolting together to check my clearances on the upper center differential bearing, and had similar troubles getting the 3rd case plate down over the input, intermediate, and center differentials. The 2 gear shafts spin nicely, but adding the center differential wouldn't allow the cover to lower. Is there a chance the intermediate shafts to center diff also feature incompatible gear profiles?

To clarify, my front output shaft and center differential gears, housing and cover were damaged. I have those parts from a parts transmission, and planned to use my original 2 gear stacks, front differential, etc. That's looking like a fool's errand lately, and I might end up using more of the parts transmission than originally thought. Not eager to to through the measurement and re-shimming process again to be honest.

Good times. I was a little put off by your use of "slimeballs," but this is highly irritating.

 

[donniekak]

Did you use a 90 center diff, with a later trans, or vice versa?

 

[JackM]

Hi Jack,
Similar question: I tried bolting together to check my clearances on the upper center differential bearing, and had similar troubles getting the 3rd case plate down over the input, intermediate, and center differentials. The 2 gear shafts spin nicely, but adding the center differential wouldn't allow the cover to lower. Is there a chance the intermediate shafts to center diff also feature incompatible gear profiles?

To clarify, my front output shaft and center differential gears, housing and cover were damaged. I have those parts from a parts transmission, and planned to use my original 2 gear stacks, front differential, etc. That's looking like a fool's errand lately, and I might end up using more of the parts transmission than originally thought. Not eager to to through the measurement and re-shimming process again to be honest.

Good times. I was a little put off by your use of "slimeballs," but this is highly irritating.

Yes 90-91 have a different center diff lower housing, intermediate shaft and 3-4 floating gear helix angle. So a 90-91 center diff can't be used in a 92-99 trans without major surgery.

 

[hotrodssnova]

If you still have your original center diff, look at the gear. You might see some small lines cut into the gear. If so, you need to find a center diff with the same marks on the gear. Jack's website has a picture of a gear with those marks. Your intermediate shaf might have the same marks also.
Another thing to watch for is the thickness of your center diff end bearing race. Its not hard to mix it up with another one of the same size. If I remember correctly, there is another race in the trans that is the same diameter, but is thicker....hopefully that will help a little.
As far as shims go, you will get to know your torque wrench real well. I measured each shaft individually..twice.

 

[markmakeitso]

Yup, all 3 of you are on the ball. New center diff housing has cuts, old one doesn't and the intermediate shaft is mark free.
The transmission in my 91 was already non-original, just described as a 1G MT AWD. This parts transmission is a 93 I believe, and seems to have the marks on the teeth tips. I'm of half a mind to rebuild the parts one then, I can probably do the shim measuring much more quickly a 2nd time.

I did a fair amount of reading before snagging a trans, but had assumed that as long as I got the correct ring/pinion tooth counts and T-case ratio I would be alright. Should have checked your site out earlier Jack.