Here's the deal

Getting ready to install a TH400 in a AMC 360 powered YJ, 39.5 Iroks, 205 Trans case (1.96 ratio), 4.56 rear gears. This jeep is an east coast trailer queen & near exclusive rock crawler (no mud interest) with amateur comp aspirations. Rarely if ever exceeds 30 mph.

I've read a bunch of the posts on this board and can now say TC theory is now slightly more clear than mud. I'm leaning toward a 1600-2000 stall, but am far from certain.

What would you use? Why? What If I bite the bullet and drop in an Atlas or stack around 4.1, does that change the choice?

Keep it low like that. If you talk to the converter company, they can build it around your application. More stall generally means more slip. Slip = Heat. There's a little more to the science, but that's the general idea. You want something that's tight, efficient, but still gives you the stall and torque multiplication you need.

I'd wanna be around 1800-2000, the 4:56 and 39.5 combo is like way tall for a crawler, thats the same as a stock 3:42 turning 30" tires, now if you go to a 5:13 or 5:38 less stall will be ok.

I'm running a 2200 stall. v6-th350-atlas 4 spd. The higher stall is nice because you can use the low gearing and not push through the brakes. 120:1 in 1st and I have no problems stopping. No issues with heat although I do run 2 tranny coolers, 1 heat sink type and 1 tube type with a fan. Hardly ever have to turn the fan on though

I like the higher stall on the trail.....but man, does it stink on the road. It makes my jeep a complete slug on the road.

very usefull input -- thank you

I'm gonna pull the trigger on the Atlas in the next week or so....

Now I debating what ratio to choose, many seem to say now lower than 4.3, due to the walk through the brakes issue.

My basic instincts say choose the lowest ratio possible and I'll be putting in a new TC as well - sounds like the lower I go (gearing), the higher (numerically) stall speed I need?

Bearing in mind I've never wheeled an auto tranny before, what ratio case t-case do you think is best and why?

Go with a 4.3 or if you have the cash, do the 4spd atlas or 3 speed stak. the lower the t-case ratio, the more you are going to want a manual valve body.

Why will I want the manual valve body? I thought that was mostly about changing the shift pattern (1st,2nd Drive instead of Drive, 2nd, 1st)

Would you still say the 4.3 ratio bearing in mind I've only got 4.56 rear gears & 39.5 tires, and am likely to go larger tires down the road?

Why will I want the manual valve body? I thought that was mostly about changing the shift pattern (1st,2nd Drive instead of Drive, 2nd, 1st)

Would you still say the 4.3 ratio bearing in mind I've only got 4.56 rear gears & 39.5 tires, and am likely to go larger tires down the road?

with the low t-case gearing, there will be times you may need to start off in 2nd or 3rd gear while in low range. The manual VB allows for this feature.

with the low t-case gearing, there will be times you may need to start off in 2nd or 3rd gear while in low range. The manual VB allows for this feature.
I just happen to have the PIMP one for sale in my sig :D

with the low t-case gearing, there will be times you may need to start off in 2nd or 3rd gear while in low range. The manual VB allows for this feature.

I get it now, I think... Dumb question I'm sure, but if you stick this tranny in 2nd gear (in stock form), does it start in 1st, shift to 2nd and then remain in 2nd regradless of engine rpm?

Is the only way to get compression braking on an auto to go with sick low gearing and the manual valve body?

If you had say 130:1 ratio and no manual vb, why could'nt you just leave the tranny in 1st and get compression braking that way?

I just happen to have the PIMP one for sale in my sig :D


That VB & TC must be really dusty in your garage by now.

Maybe its time to sell the combo for next to nothing to some east coaster who feeling the pinch of a project that is getting more expensive every day, (why does it always end up that way?)


Think of it as charity or as bringing the country together (you pick). :D