and a pic after the skid went on

 

Joe,.. -looks great, and thanks for the real helpful write-up!.. I'm gonna check out Terra Low to see if they make a Dana 300 kit... And that's MY old D20 in those photos?.. I can't understand why you'd want to paint over the nice rust, grease and sawdust coating I put on it. ...to each his own, I guess.

 

Joe:
Thanks for the detailed writup. What Tera low kit did you order? I understood there to be one Dana20 kit for the input of the manual trannies and another one "planned" for the autos. This kit mates right up to your th400/D20 adapter gear...cool. What did it end up costing you price-wise? I wanna put this in my CJ7 th400/Dana20...can't wait to hear how it crawled on the trail.

Shain

 

That's your old 20 in there, Brian!! Wahoo! She ran great with the new gears!

I ordered the Tera gears through TrailQuest.com. They had a guy up at the RAID. I just called the number off of their web site since I didn't talk to or have the guy's number. Tera sent the gears direct from their warehouse or mfg facility. They have had a kit for the Dana 300 for a while but I don't know if it's for sticks or autos or available for both. For the Dana 20 Auto kit, I just specified that this was for a Jeep Dana 20, 15 spline, TH 400 automatic. It was $760. I believe the auto is $100 more than the 6 or 10 spline (I've heard both somewhere) stick versions because you're getting the output gear for the adapter too. All of the gears are replaced and the kit comes with gaskets and seals. The only thing you need to buy separately is the bearings /wwwthreads_images/icons/frown.gif. Those ran $47 at a CarQuest. I just gave them the Timken part number and they pulled them that way. The first parts store (Auto Zone) did the typical "what's the vehicle?" thing and of course, could not find anything in his computer even though I gave him the specific bearing and race numbers. I know there's a million and one parts and every parst guy can't know 'em all, but Geeeeeezz! Oh, and Tera says that since they don't know what all autos may have been used, they have somewhat of a disclaimer on the parts being right. If you have your case out, the best bet is to count the inside splines on the output gear of the adapter to the TH400. I know of a guy who has been running a TeraLow in his CJ-7 w/ a Dana 300. I'd just met him on a trail run a few weeks ago and didn't get the details on his rig so I'm not sure if it's an auto or a 4 speed. I'll be going over my rig on Friday making sure all the pieces are still there, and if nothing else has to be done except sweep out the gravel, I may be going out again on Sunday. He's supposed to be on that run. I'll get more info about transmissions..

As for the trail run today, it was good. I'm going to be short here tonight (yeah right). I'm "done" for the day. I'm running a 231 V6, a stock TH400 (2.5:1 1st gear) and 3.73:1 diffs, Goodyear Wrangler AT (31x10.50) on custom Stockton 15x7 wheels. The first of the other two Jeepsters on this trip has the "twin sister" 231, 4.88 gears in the diffs and 2.7 something:1 1st gear, an ARB and a PowrLok w/ 31" BFG Mud TAs and the other has 4.88s, 3.0:1 1st gear , two PowrLoks and 33x9.50 Mud TAs. (All of us running TH400s). . We did several tach comparisons in various situations and were at the same RPM whether going up or down hills. Two of our Jeeps have identical 231 V6s built at the same time. I believe the other was a 225. Downhill hold was great and I rarely ever had to look for the brake pedal. I only got my butt kicked on one hill climb that was a stretch of moguls, one after another for maybe a 100 ft on a fairly steep hill. Halfway up I just dug in. I gave it two tries and then whimperd over to the go-around /wwwthreads_images/icons/blush.gif, which was equally steep and rocky, just not dug up. The Jeep crawled right up with barely a tire slip in one spot. Everywhere else, my Jeep kept pace with the two other, lower geared (diffs) Jeepsters with Lockers/ PowerLoks front and rear.

This trail run was to start out taking us up Kingston Peak, from the Tolland side and over to the St Mary's Glacier side, trying every hill and rock run we could to test out the new gears. We didn't quite make that as you'll see in the first pic (Mel's white '70 convt leading, followed by my red convt w/ top down in the middle, and Ron's screaming yellow wagon bringing up the rear). The snow was closing in as we progressed up the trail. There's a 4x4 truck way ahead of us, who'd got stuck in a few places and slid off the edge with a tire, and he churned up the snow where it'd pulled us towrd the edge as we went through. Mel walked up ahead of that truck where he could see that a snow field had covered the final ascent over the peak. We probably could have winched through (anchored to what?) but it was clear that the trail is most likley closed for the season unless the next few weeks are really warm. That side of the mountain won't get much sun at all until next Spring. Rather than risk any damage on hidden rocks on that ascent, we turned around and went around the mountain to some other trails. All in all, it was a good run. Not an overly challenging ride, but enjoyable none the less.

I'll be putting together some spreadsheet data I'd worked up a few years ago, on the gearing and final drive ratio comparisons, along with mix and matching those with different tire sizes. The work is already done. I just need to plug in some values to cover the ranges from nearly stock rigs to heavily modified (w/big-a$$ tires and +++). That sounds like a Sunday evening thing. It'll give you guys some idea on how much difference this gear and that gear with this tire and that tire really makes.

All in all, I'm happy I went with the TeraLow gears. I just wished that I didn't have to re-engineer the decal (and the only decal on my rig) I'd put up the rear up-kick up the skid plate (pic in above post)

Yehaa!

 

Man, Joe, that would be a HUGE bonus to a lot of people if you put all those numbers together on different gearing/tach numbers/tires, etc.. -Would have saved many of us a lot of experimenting time and money. Good on ya!

 

I'm confused...as usual.
Alright this is concerning the th400/Dana20 setup in my CJ7. The tailshaft of my th400 is a 30 (?) spline (I'm almost positive it is) , that mates to the factory adapter with a big gear on the rear of it, that gear fits in my D20. This tranny used to mated to a quadratrac and the th400 had the long 10 splined output. I swapped that out to a 30(?) splined output to mate to the th400/Dana20 factory adapter so I could ditch the chain driven q-trac.
Where does the 15 spline count you mentioned come into play? Is that the number of teeth on the adpater gear? I just replaced my adapter and adapter gear with another junk yard one out of a J series pickup with the th400/D20 combo. It fit up just fine. I swear I think the inside splines of the new adapter gear where like 30 splines again. Is the tailshaft of your th400 15 splines? Am I a moron that just can't count?? I'm so confused /wwwthreads_images/icons/crazy.gif.

I read in you first post that you bench tested tha fit of the new gears by using a spare adapter and gear (maybe thats not what you said but that what my feeble brain interpreted /wwwthreads_images/icons/crazy.gif). But then I thought I read that you got a new adapter gear with the Tera kit, or is that a new gear in the Dana20 that mates to the stock adapter gear?

I'm sorry for all the questions, I've just managed to thoroughly confuse myself.
Thanks again for all the info.
Shain

 

What's this? You want me to write it down so you can understand it? Seriously, I'll try again. I don't mind trying to write this so you can understand. I'd just done a brain dump without a whole lot of thought and organization. I'm surprised you were able to get that much out of my gibberish (sp?).

You're right. We did bench test the D20 with a TH400 to D20 adapter, using the NEW output gear for the adapter. The output gear in the adapter gets replaced. That gear (old and new) has 15 splines on the INSIDE. The TH400 does have 30 splines but when you look at what drives what (with theD20s tail piece off) w/ the case in 2 High, it will make sense. Mel and i also thought the kit should have a "30 spline" at first, until I took the tail piece off of the D20 we were building and counted the inside splines of the adapter's output gear. It's not the external teeth on that gear, but the internal splines that matter. If this helps, great. If not, I can try to shoot some dig-pics over the weekend of the inside of the case, from the tail side, plus the output gear in the adapter, which may help clear this up.

Joe

PS I don't know if I'm considered a part of the "new class". I generally don't have much to say unless I think it will make a difference. I've been a regular visitor to the board since before it went to this format and only more recently, have I jumped in more. It's true though. The names seem to be a changin' as time passes. maybe as we get our rigs far enough along we tend to go out and run 'em more than try to figure out "how to" do this or that or find pieces/parts. It's a good bunch here on the board with some real "smarts" between the lot of us.

 

Sorry Joe, I'm just dummer than dirt! My feeble brain says that the output shaft's spline count determines the xfer case's input gear spline count. As many of my friends already know, I'm visually impaired, even though I have 20/20 vision. If you could post a diagram, maybe even a bear of very little brain, such as I could figure it out. But don't stake anything on it. Thanks for all your very valuable information.

Tim
'66 Jeepster Commando w/Buick 252/4.1L V-6
'70 Wagoneer w/Buick 350 V-8

 

I know it seems illogical, but the 15 spline thing is right. I'll take some pics sunday eve when I get back.

In the meantime, here's some gearing comparisons. I'll cut out the formulas and attach an Excel spreadsheet in a lower version, 5.0 which most people would have ( or I can post it in Office 2000 version) and you all can play at will with different tire sizes, speeds and such. I chose 3mph because most of my low range 4 wheeling is done pretty slow.

Please forgive the loss of formatting below. I tried to "edit" it and put the spacing back in between columns, but that didn't work. I put in a / between fields. Hope that makes it easier to read

Low Range Comparo
Final Drive.... Axle Ratio......TH400
........................................1st Gear....T Case Low Ratio Speed.....Tire Dia............ RPM
18.93...............3.73...............2.5...............2.03............... 3...............29...................695
29.37...............3.73...............2.5...............3.15............... 3...............29.................1079
21.67...............4.27...............2.5...............2.03............... 3...............29...................796
33.63...............4.27...............2.5...............3.15................3...............29.................1235
24.77...............4.88...............2.5...............2.03............... 3...............29...................910
38.43...............4.88...............2.5...............3.15............... 3...............29..................1411
............................................TH400
Final Drive.....Axle Ratio...... 1st Gear.......T Case Low .....Speed......Tire Diameter......RPM
18.93............... 3.73...............2.5...............2.03............... 3............... 30.5................ 661
29.37............... 3.73...............2.5...............3.15............... 3...............30.5............... 1026
21.67................4.27...............2.5...............2.03............... 3...............30.5................. 757
33.63................4.27...............2.5...............3.15............... 3...............30.5................1174
24.77................4.88...............2.5...............2.03............... 3...............30.5................. 865
38.43............... 4.88...............2.5...............3.15................3...............30.5...............1342
............................................TH400
Final Drive.....Axle Ratio.......1st Gear.......T Case Low.....Speed.......Tire Diameter....... RPM
18.93...............3.73............... 2.5...............2.03............... 3............... 32.5................... 620
29.37...............3.73............... 2.5...............3.15............... 3............... 32.5................... 963
21.67...............4.27............... 2.5...............2.03............... 3................ 32.5.................. 710
33.63...............4.27................2.5...............3.15............... 3............... 32.5................. 1102
24.77...............4.88v...............2.5...............2.03............... 3............... 32.5.................. 812
38.43...............4.88............... 2.5...............3.15............... 3............... 32.5............... 1259

 

AHAH...now I understand...I think /wwwthreads_images/icons/crazy.gif. I went and pulled my old busted adapter with its gear out of storage and looked at it. Now what your telling me makes sense. The adapter gear on the transmission side accepts the 30 spline th400 output. On the t-case side, it has the large gear I remembered, but it also has a smaller 15 splined (imagine that!) gear attached to it or part of it...if that makes sense. That 15 splined gear is what turns the mainshaft gear that operates your rear output all the time... regardless of what gear your in. The sliding gears, in turn, move back and forth to their various positions depending on whether of not your in 2HI, 4HI or 4LO, but that 15 spline gear always fits inside the mainshaft gear and turns the rear output. Is that right? I know my lack of t-case knowledge is shinning through, but know I think I understand what you are saying /wwwthreads_images/icons/smile.gif. Like you said, the 15 spline Tera low kit for th400/D20 is what I need. Now if I could just round up the 800 bones...
Thanks again,
Shain

 

By golly, I think you've got it! I'm going to take some pics when Mel does his T case. I'll be able to show the inside where you need to grind for the new gears and the install sequence. I didn't have the digi-cam until my case was ready to go in. If you have the JP article on this project, it'll help. If not, I'll scrounge throught the last few month's mags to find it and scan and post it.

Joe

 

COOL on the digi-photos... that would be great. I've got the JP article stashed somewhere amongst the piles of magazines my wife loves so much /wwwthreads_images/icons/laugh.gif
Shain

 

Just to let you know not all cases have to be ground for the intermediate gear to fit but some do.
There are lots of casting variations in the cases so as was mentioned always double check fit before
doing the final installation of the seals, etc. Excellent write up by the way. Nickmil.