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MUA5 Transmission to Transfer Case Seal and Synchro questions

370 Views 8 Replies 3 Participants Last post by  Enemigo
Hello Gentleman.

First time post here. I've been lurking quite a long time as I purchased a very clean 2002 Trooper limited with a dead 4L30E for next to nothing about a year ago. I did a good bit of reading on 4L30e problems and repairs hoping it was repairable but full well knowing I might be pulling it out. And if I was pulling it out, well... a 5 speed was going to be going in in its place. After lots of reading here and finding a promising 5 speed from a 98 3.2L amigo I found at a yard nearby... Suffice it to say I've embarked on the 2nd option.

I genetically inherited the "while you're in there" disease from my father and decided to take a crack at installing the Revolution Gear 3:1 low gears in addition to doing the engine's rear main seal, and the front output shaft seal cough "while I'm in there." Upon reading as many forums as I could about the process I've stumbled across a few forums mentioning the seal between the transmission and T case failing and letting all the trans fluid leak into the T case. At the moment have the T case completely stripped down and ready to clean and reassemble with the new Low gears. My "while I'm in there" disease is screaming at me and telling me to replace this seal between the Trans and T case since I am literally able to lay eyes and hands on it as we speak. However I can't find any info on a part number. Just the mention of a mystical forum member named "Jerry" mentioned here.

Does anyone have any Intel or P/N on this seal or know who said "Jerry" is? With 140k miles on the clock of the 98 amigo donor I'd love to freshen up anything that is cheap and easy, like this seal.

Additionally another puzzle; while looking as photos from forums documenting the 3:1 gear swap I noticed something. The dog-toothed gear (I don't know the correct term, please educate) that sets on the top of the shaft (engages low range gears) that comes in from the transmission has 3 blank slots where some small keys COULD sit. (mine pictured below)
Gear Crankset Bicycle part Automotive tire Wood

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I say could because I did have them on the same dog-toothed gear that sits on the 3'rd shaft that engages the front output for 4wd along with some kind of synchro mechanism. (mine pictured Below with keys removed)

Camera lens Camera accessory Cameras & optics Lens Teleconverter

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On Revolution Gear's own ebay listing there's a shot of a transfer case that Doesn't have them on the primary input shaft (like mine). And another shot of one that does with the addition of some kind of brass toothed plate. (photos of both below).

Automotive tire Machine Differential Motor vehicle Auto part
Automotive tire Motor vehicle Gear Bicycle part Automotive design

I guess what I'm asking is, is it ok that mine lacks all that? Did some T cases have synced 4wd engage and others didn't? Additionally do I have the option of putting in a synchro'ed 4wd lock if I source such parts. I'm not that interested in upgrading unless someone on here convinces me, I'm just looking to put my mind at ease that someone hasn't been in here before and left some parts out before I reassemble.

Thank you for your time, wisdom and intel. I've really appreciated this community at a distance and am excited to finally engage with y'all.



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I think I found Jerry. JLEMOND. The guy seems to really know his stuff round these parts. I hope he finds this (y) Also, Correction, I misspoke in my last paragraph. The missing teeth and synchro stuff on mine Is for the lo-hi, not the 4wd. The 4wd has the teeth and sync stuff.
Did you bump into my install thread in your searches?

On page one it talks about that thin gear, which you don't need after you install the low gears. On page three you can see me install those dogteeth gears backwards and then I had to pull the entire case again to fix it. I'm very good at doing things once, then forgetting everything I've done until I refresh my memory by reading my own thread, so I can't be as helpful as I'd like to be. :/
Hey Enemigo! Thanks for the reply. I actually came across your writeup before I ever purchased the gears. It was well done and super helpful, so thank you for making it. I do remember the part about the thin gear which you don't need anymore. I believed that was referring to the one "quieter gear" on the 3rd shaft connecting to the front output flange. I was referring to that brass one on the 1st input shaft of the last photo I Posted from Revolution Gear's ebay page. I don't have one, or the little keys that go in the 3 gaps. HOWEVER, upon reinspecting your writeup, I was able to see that the dog gear on your input shaft also does not have the 3 keys and circular spring either. Which brings me relief. I'll likely move on from that worry. Here's the photo from your thread that showed me yours was like mine.

I remember your struggle with the dog tooth gears as well. I didn't bump the thread as... well... as many years as I've spent forum lurking, Im kind of new to actually posting and interacting and didn't know the etiquette. Some people get bent out of shape when you reawaken a dormant thread or hijack topics. Others get bent out of shape for starting a whole new thread. 😅 I just didn't want to misstep. If you think it would get responses faster to bump that thread I can but I hate to make a duplicate post now.

I feel you about the memory struggles of these types of activities. It's been 2 months since I cracked this t case open and I fear if I don't hurry up and put it back together I'll never remember how. 😂

Do you happen to have any intel on how to track down that seal that goes around the shaft between the t case and the transmission? Did you replace yours? If you didn't Have you had any trouble with failures?

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Yes, mine is a 2002 but it was an auto. I'm swapping in a 5 speed out of a 98 amigo 3.2L. My understanding is the AR5 and the MUA5 are quite different units. You are correct in that the MUA T case is integrated into the transmission. However the 2 halves remain separated internally and each have their own oil supply. Here's a pic below of the seal that separates them (t case side).

Light Automotive tire Black Motor vehicle Alloy wheel

There's one part of me that's ready to just drill a hole through it, run a screw in it and pull it out. If I could just turn it over I'll see the Part Number. My only fears are 1: what if I drill through the part number (would be just my luck). And 2: what if I can no longer source a new seal (would "also" be just my luck). I'd PM JLEMOND but I'm still too new of a member. I have to make a certain number of posts before I'm allowed to PM people. If you'd be willing to shoot him a PM and send him towards this thread I'd be hugely grateful. Otherwise I'll just keep puttering around and making friends and comments on here until I can PM people 😂
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wPine. Brother, thank you so much for putting me in touch. You're a lifesaver. I need to get this puppy put back together. My current daily driver is swiftly on the decline.
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