Best t-case for this app?

Rich

Rich

Asshole at large
Joined
Mar 17, 2005
Location
Central PA
Was thinking about it this morning, and my previous t-case setup was almost too deep before:

3.06 1st gear 4.7 t-case 4.11 diff, 38.5's - 59:1
It worked great in really slow, technical stuff, but for 90% of what I was doing, it was too slow.. most of the time, even slowly, was spent in second gear, close to the downshift point to first, and it would frequently drop to first right as I touched a rock, which was really annoying.

Now, if I change nothing else:
3.06 1st gear 4.7 t-case 6.72 diff, 39's-42's - 96:1 (!)
That's too deep. it's going to be a PITA to hold it stopped, I'll be in OD going ~10mph in low range, etc, etc..

I think ~45-50:1 would be good, which means 2.19-2.43:1 in the case.
If I'm gonna swap, I'd like to upgrade...
  • MUST be gear drive, and at least as strong as a Toyota gear drive t-case
  • Front dig capability would be nice, but certainly NOT necessary.
  • Price is, of course, an issue.
Current setup is a 21-spline Toyota minitruck case. Using an AA adapter between the TH350 and the Toy case (The output shaft in the trans makes it look like a TH350), with a clocking ring between the trans and the t-case adapter.
Some ideas, keeping in mind.. deeper diff gearing is significantly easier on t-case parts:
  1. Toyota t-case, 2.28 stock gearing, 23 spline upgraded input, upgraded output. Est. cost - $400-500, and it's a pretty damn strong little case.
  2. Dana300 - need an adapter, output flanges, HD outputs(?), and make shifters.. $1k? It's a little more than I wanted.. 54:1, which is damn near what I had before..
  3. NP205 - - need an adapter, output flanges, and make shifters.. $750, but it's a little under-geared... 40:1, but I'm not gonna break that SOB.
Is the 300 THAT much of an upgrade? Would the reduced cost of the 205 be worth the reduced gearing?
Any other cases I overlooked?
 
you are going to have bigger tires too, so that 54.1 is going to feel different.

you build the outputs of the d300, your gears will be the weak link. ask mr. nuts.

205 is sturdy and cheap, but might not be low enough. you could always go 205, then do a 3.1 low range kit later if it isnt low enough.

i like the idea of the built up yota case. small, and light weight. you can't get front digs out of that though. and will it last behind the new motor?

in the end i would end up with a 205 probobly, b/c of cost and ability to twin stick it. and the fact that you dont have to do anything to it, just buy and adapter.
 
i'd do a 205 if anything. i don't consider a d300 much if any of an upgrade over a toy gear drive.
 
anyone else?
 
205, if that ends up not enough gearing, put a 203 in front of it.

When I had the CJ buggy, I found myself using single low more often than double. And it was running a bigger and much heavier set of tires.

The only downside I see, is its heavy, but you won't have to worry about hurting it.
 
how about you run what you got and then make a decision? 96:1 with a 42" tire may be right for you.

Also what about putting the stock gears in the toy case?

(and you wont have to fork out any $$)
 
I am sure that you could find a toyota guy to swap cases with and probably put cash in your pocket.
 
Atlas 2 ?

I know they're not cheap,but they're light, gear driven, twin sticked, and come in ranges from 2.0 to over 5.0 last I looked. If you decide to modify something else - the amount you may spend may not be much different than a new Atlas 2.

I liked the idea of trying out what you have as a starting point.

The crawl ratio formula I'm looking at right now doesn't include tire diameter. With 42's you might want a higher ratio.
 
I thought you had a 700r4 ? your using those numbers (3.06) in your calcs?

Run the numbers with a TH350 ~2.48ish 1st? That might give you enough to fix things and give you a cheaper tranny.. ??

I do know what you mean about jumping throught the 1-2 shifts all the time.. I had considered if/when my tranny acts up to simply put a TH350 in it.. I'm pretty sure the adapter will swap over and clear up some front shaft issues..
 
I like the 700R.. it's not going anywhere.. got too much in it.

Front shaft issues? not me. :D
 
you can twin stick a toyota case, now whether or not that will help you do front digs is another story, i think it is about $200 bones. and if you want stock gears ill trade you cases, don't worry about paying me, thats what pals are for.
 
Cperry said:
if you want stock gears ill trade you cases, don't worry about paying me, thats what pals are for.
Click to expand...

What a pal! I would trade for a 23-spline stock geared case with an upgraded output though.. :)

Currently running a twin-stick on my case, but it only gives RWD low, no FWD options available.
 
Rich,

EDIT: Guess you can't upload spreadsheets - I'll pm it to you.

Hopefully my spreadsheet upload worked - I really dug into the gearing selection process - wanting rock/mud/street gearing. Play with the spreadsheet I created and see if it helps. Also, the single best gearing selection web page I've seen is
http://www.grimmjeeper.com/gears.html
I found crawl ratios by themselves to be useless because they didn't account for tire size.
Stewart
 
Thanks Stewart.. I've always just take the crawl ratio and divided by the tire size.. gives me an abstract number to compare to a baseline.. But hot damn, I just looked at your webpage... impressive work! :beer:
 
Stak, I mean you are already redoing the whole thing anyway. Go ahead and grab a 3 speed stak and call it good. I wasted my money building up a 300 and I still have more to go. With the cash in it I am close to a two speed stak after I finish the output upgrade. I don't really think that 54:1 is low. Having to go to second gear for non tech stuff is a great option. I would rather do that then to not have the low gears when you need it.
 
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