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TeraFlex Low 18 3.15 gears in Dana Spicer Model 18

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bobevans View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jan. 2019 at 6:03am
I ended up grinding just about 1/2" off of the inside end of the front axle shift rail. The first picture is the rail all the way in (front axle engaged) after grinding about 1/3" off. I then decided to take the full 1/2" off. The other pic is with the axle disengaged - the rail is still being supported by the thickness of the case after taking the rest off, but it's close. Thanks to Ken for pointing out that installing the poppet balls and springs shows you just where the rails need to go.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jan. 2019 at 6:11am
As usual, I thought I was about done long before I actually finished. I had installed the shift rail seals and then ended up having to take the rails back out a couple of times. After just about tearing the seal on the deep pocket in the rail that holds the shift levers I made an insert from a piece of old wooden dowel rod. It worked surprisingly well.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jan. 2019 at 6:15am
This pic shows the amount of grinding needed on the underdrive shift fork to allow the sliding gear spin freely.
I ended up using the Allen head set screw and some Loc-tite to hold the fork to the rail.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 3A Steve Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jan. 2019 at 1:31pm
Your picture of the speedometer gears makes reminds me of my experience. Got my 3A back with one of Herm's D-18 TeraLows. Driving home from the shop I was amazed at how much faster the Willys went. Hit 65 MPH and still climbing. Didn't take too long to figure out that the "new" transfer case came with its previous life's speedometer gear. Luckily I had a box full of gears from a previous failed project. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jan. 2019 at 7:44pm
I would follow those Tera Low instructions with some caution.
I used to claim the same thing as Tera Flex; but more recently I discovered that at least  some of the 2.46 ratio small hole D18 castings will  accept the 3.15 intermediate gear with very minimal grinding.
In fact it may be desirable for guys with T90 transmissions since it eliminates the need for the T86AA rear bearing adapter ring.

Apparently the short shift rods were made at various lengths.
This pic looks exactly like my rod before trimming off 1/8".

And this pic looks exactly like my rod after trimming off 1/8"...

As I stated elsewhere... I had sufficient clearance for my sliding gear shift fork without needing to grind.
Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963)
Zero aftermarket parts

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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan. 2019 at 3:03am
Ken, a couple of quick questions. I guess I'm going to need T86AA bearing adapter? I'm seeing them for right around $30 on eBay. Will I need to pull the transmission to hook everything up?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jan. 2019 at 4:10pm
As you know the T86AA has the same basic internal transmission dimensions as the T90.
T86AA case has exact same rear pattern (Texas) as the T90.
Therefore it also used 90 sized main shaft bearing. (Fafnir 307 K)

Jeep designed the T86AA rear adapter ring to fill the void caused when installing the 307 series ball bearing into a big hole TC which is designed to accept the larger 308 series ball bearing.

Here are a couple rings that I currently see in ebay....

To install the T86AA adapter ring you need to remove the main shaft gear (TC input gear) then remove the standard rear bearing ring.
The snap ring you see in pic is to hold 307 bearing into the adapter ring bore.
Jeep Part # 928447


Edited by oldtime - 22 Jan. 2019 at 1:08am
Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963)
Zero aftermarket parts

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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jan. 2019 at 4:42am
Perfect! That's one I was looking at on eBay. So I'll try to leave the transmission in place when swapping transfer cases.
Thank you again.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jan. 2019 at 3:33pm
Yes leave transmission in place on the engine.
Obviously you will need to remove the T90 mainshaft nut.

That can best be accomplished by putting the transmission into highest gear and then remove the shift tower.
After removing shift tower.... manually slide the 1st/ reverse gear into either 1st or reverse.
That puts the T90 into two gears at a time and thereby locks the main shaft up tightly so that you can readily remove the main shaft nut.

Upon re-assembly be sure to shift all gears back to neutral positions before putting the neutral shift tower back on. 
You can tap on the front synchronizer hub to get the hub back into neutral position.
Typically shift towers are removed and reinstalled being shifted in neutral position............


Edited by oldtime - 22 Jan. 2019 at 3:39pm
Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963)
Zero aftermarket parts

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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jan. 2019 at 3:47am
Awesome. Thank you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 52 M38 Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar. 2019 at 1:50am
Originally posted by AKoller AKoller wrote:

Thanks for the post. I am planning on a Terralow upgrade this year on my Jeep. I have a big mouth (4") Dana 18 out of a late 60's CJ5 I will use. I will also replace the 2nd gear and synchro's in my T90 at that time to try to solve the jumping out of 2nd problem I currently have. I hope to have this done before the FCT in September if I'm lucky enough to get drawn to go.

To stop it jumping out of second you need to shim the shaft at the back of the case to remove the play. The fore/aft play in the shaft allows the two piece shaft to slide apart slightly, allowing the second gear to skip out. Mine does it too despite having less than 3,000 miles on the guts.  I haven’t gotten around to taking it out again. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr. 2019 at 3:27am
So I spent a very frustrating Saturday trying to get my cool, new, low geared transfer case in my 2A. I'll get to a couple of issues, but just to put all the info in one place, I have a picture of how the T86AA bearing retainer sits. Ken says it should be a light press fit, but my new Crown part took some fairly serious persuasion to fit into the transfer case and then to seat the bearing into the retainer. I used some fine stones in the die grinder and some 320 grit wet/dry sandpaper to get the Fafnir bearing into the retainer and then on the out side of the retainer into the case with a mild press fit. I still had to hammer a little - nice, light(ish) taps
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr. 2019 at 3:44am
I got everything ready, set my "new" transfer case on a transmission jack and cranked her into place where I had just removed my old Dana 18 transfer case. after a fair amount of swearing and switching to a couple of different jacks, lots of wiggling, more swearing, I still couldn't get the transfer case tightened down. There was probably close to a 1/4" gap between the x-case and the T90 transmission. I gave up and took the X-case back out and left it for the night. Next day I was staring at the stupid thing, wondering why it wouldn't seat down when I noticed two distinct circular marks on the front of the x-case. That's when I realized that the case I was using (Out of, I was told, a mid-seventies CJ5) had no "relief chamber" in it to accommodate the reverse idler and cluster gears shafts and the little plate that sticks out of the back of the T90 transmission.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr. 2019 at 3:50am
I will apologize now for the RTV in the picture, but remember gentle reader, this was after 4 or 5 tries of placing, tightening, removing and trying again to seat the case. on the last two or so attempts I had resorted to pulling the case back far enough to get a finger full of RTV onto the mounting surface.

After realizing the issue,To remedy this, I ground off as much of the shafts as I dared and ground into the front of the x-case. Luckily, it looks plenty thick in this spot.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr. 2019 at 3:55am
The T86AA bearing retainer (which is in the front of the case in the above pic)is wide enough to give you trouble if you have the bigger tie plate tapped into the back of your T90 trans. I was fully expecting that, but was surprised by the lack of a relief chamber in the large hole x-case casting. The larger bearing retainer also interferes with included gaskets in the parts kits, so I was cutting one to fit in the above pic.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr. 2019 at 4:03am
Before assembling, I did put the bearing into the retainer, set the snap ring and seat it onto the back of the T90. I then measured the play in the main shaft of the T90. Rick Stivers, in his T90 trouble shooting video, suggests that this can be shimmed to keep everything tight and keep your trans from popping out of second gear. As an aside, if you haven't watched his video on YouTube, give it an eyeballing. My shaft had a little play, so I found that the snap ring on the front input shaft of the T90 is just about perfect diameter. It took a little sand paper work to get mine just the right thickness, but that coupled with tightening up my 2nd/3rd shift fork and I haven't popped out of second yet!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr. 2019 at 4:13am
After scraping off the RTV and placing gasket sealer, I made a couple of studs for the two top mounting bolts on the back of the T-90, removed the cross member and lowered the back of the T90 as much as I could, set up my jack again and gave it another try. This insert went much more smoothly (although one of the studs wouldn't come back out, so I had to add a couple of washers and left it in place - only one Bubba -so far)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobevans Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr. 2019 at 4:25am
The next challenge occurred when I went to hook back up the clutch bellcrank. I was all happy when my new case had a hole already tapped for the bellcrank ball to thread into, but when I went hook up the tube, it was at least 1/2" too long. I took a look at my old D18 and the ball stud is pretty much just flat on the end of the case. My "new" case has a raised boss that is tapped. You can't just cut the end of the tube to fit because the ends are set up to accommodate the balls and lever arms. Bring out the cut-off wheel and cut 1/2" out of the middle of the torque tube bell crank thingy and weld it back together. luckily I had a piece of one the shift fork rails and it fit perfectly inside the hollow bell crank tube and kept everything nice and straight while welding. Oh yeah, and then the clutch cable fell off of the end of the throw out bearing fork. Luckily the fork stayed in place, so just a small amount of swearing and it was back in place.


Edited by bobevans - 02 Apr. 2019 at 4:51am
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