Calling all T90 Experts

[timjuhl]

I spent some time poking into the innards of my tranny today. When I was driving it last fall, I noticed a tendency to grind gears a bit shifting from 1st to 2nd if I had the revs too high. 2nd to 3rd was OK as was 3rd to 2nd. I never tried shifting into 1st unless stopped.

Anyway, since the tub is off the frame anyway, I thought it might be interesting to pull the top off the tranny. I took a picture of what I found and want to know if the visible wear is within "normal" parameters or whether I should be making some repairs at this time.

All observations, comments and suggestions are welcome.

Sorry it is so big - I wanted you to see the detail. It is also posted on photobucket (link below)


http://i30.photobucket.com/albums/c318/champ81L/Jeep/Tranny.jpg
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Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft

[wesk]

Hello Tim,

I reduced the size of your photo from 465K to 78K and lost no significant detail. I gotta be fair to the entire group! I also opened an album for you right here on our web site. Our photo albums load hi def pics but store then in three sizes, thumbnail, 1/4 size and full size. The photo I placed in your post is the 1/4 size. Your album is at:
http://www.willysmjeeps.com/v2/modules.php?set_albumName=album183&op=modload&name=gallery&file=index&include=view_album.php

There is no apparent wear there that would cause a grinding issue at higher shifting RPM's. The usual cause for that problem is either the clutch is not releasing fully or the oil is too thick.
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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

[timjuhl]

You're right about the pix size. I won't do it again.

Thanks for your observations about the tranny. I plan to refill it with 90 weight mineral oil which is sold for the trannys of old Ford Tractors. No additives of any kind. I'll use the same stuff with the transfer case.

I seem to remember a discussion where it was said there is some mixing of fluid between the tranny and transfer case. Is that correct?

Thanks again!

Tim
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Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft

[wesk]

It can migrate from the tranny to the transfer on some T90/D18 combinations.
_________________
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

[oilleaker1]

2nd gear is shot. The drive dogs should have no taper and look like a new brass synchro. Yours have bad taper and are all chipped and broken. I'm surprised it doesn't jump out of 2nd on you. The synchro collar that engauges the dogs may also be bad unless it was just replaced, but I'd take a look at them. John

[timjuhl]

John,
I assume when you talk about the worn and chipped "dogs" you are referring to the area of 2nd gear that is just adjacent to the brass gear, correct?

And no, it does not jump out of gear.... it doesn't even grind all the time

I just figured if I needed to do something that it would be easier with the tub off to get at it. I appreciate the input.

Thanks!

Tim
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Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft

[timjuhl]

This is the tranny from my parts Jeep. It is also a T90A-1. To my untrained eye it looks to be in better condition and I'm thinking of swapping it out for the other one.

For those who know T90's, what do you think?

Tim


_________________
Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft

[oilleaker1]

Tim, yes, the teeth next to the brass synchro teeth. The 2nd transmission has a much better 2nd gear and a worse 3rd. The 1st/Reverse slider is better in the 2nd tranny. You could just build the best out of the two and check for rough bearings while there. When the "drive dogs" have one side of the point that angles and is worn, that is called taper. Taper helps it slip back out of gear like a sliding surface. The inside of the collar that slides between 2nd and 3rd has the points on the inside. Those should be looked at also. It's a large amount of work as you know to take them in and out for testing. Your decision. Everything associated with them is a large amount of work! John

[jimm]

If you dive in on a rebuild, I recommend this rebuilding guide: http://www.cj-3a.com/T-90%20Rebuild.htm

Here is an description of the relationship of the fluid levels between the tranny and the transfer: http://www.cj3a.info/tech/fluid.html
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Jim McKim
1952 M38 son-father project
Slowly turning rusty parts into OD parts

[wesk]

That's Rick Stiver's rebuild guide. It's in our links at his original location on Willys Tech. The CJ3A page is just a relay link to the same guide.
http://www.willystech.com/wt/T90RebuildGuide/T90rebuild.htm

It's the best guide out there as is Rick's D18 rebuild guide at:
http://www.willystech.com/wt/Model18TCase/Model18TransferCase.html

John,

Good thing you spoke up. I must have been half asleep when I first viewed Tim's photo. Rick's photo below from Frankie Ladwig make it easier to evaluate the assembly.


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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

[timjuhl]

Thanks to all for sharing your expertise and suggestions. I appreciate the "education." We're going to pull the tranny out of the parts Jeep today and give it a closer inspection before deciding how to proceed.

Who knows, maybe I'll get this thing back on the road before winter

Tim
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Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft

[oilleaker1]

A good thing to do is study the tutorials before you tackle one. I learned a few tricks from a tranny shop owner near me. A good broken down view of the parts is a must, and a chronological approach is needed. I made a dummy shaft out of hardwood dowell for the cluster gear that also holds the thrust bearings. The main , cluster, and 1st/reverse shaft tap out to the rear. The hardest part about assembly and dissassembly is the oil slinger that is supposed to just come out after the cluster is dropped---------------yea right. It won't. That is why most are all bent up. The trick is to pull the front bearing off the input shaft while still in the case. There is a puller with a small curved ring that grabs the snap ring slot to do this. I borrow the tranny shops puller . Then you have a friend to hold the mainshaft while you tap the bearing back on while assembling. If you buy parts, The NOS USA made ones are the best, they fit much tighter, and actually fit. If your 1st/ reverse was noisy, it still will be noisy if you put them back in, even with a new cluster. Some of the new clusters do not have the cut in the end that the thrust washer tab engauges. YOU have to grind it in yourself! They are tempermental devices! John

[chuck]

I just finished rebuilding mine with great results if you follow Rick's guide and video. Herm sells the major rebuild kits and said they're the same as Novak's for a lot less money. Without a doubt, put in a new 2nd gear!

[artificer]

I too wonder why your 2nd was not jumpimng out. This one was & this is a common cause.
Grinding could be a number of things including a tight [not lubed] flywheel/spigot bushing.


_________________
John GIBBINS
ASE Master Medium/Heavy Truck & Auto Technician 2002 USA
Licensed Motor Mechanic NSW # MVIC 49593 Current
YOU CAN'T TROUBLESHOOT WHAT YOU DON'T UNDERSTAND

[timjuhl]

I guess I was lucky. Aside from the occasional grinding it never jumped out of gear, even once!

Again, thanks to all for the wonderful education. One reason I decided to restore a Jeep is because I like to be challenged to learn new things.... I think the Transmission presents that opportunity in spades!

Tim
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Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft