Opinions on Trans/Case options - Auto + single case or manual + duals?

[paulevans76]

I've got a fun beater trooper trail rig. I still drive it to and from the trails and usually it does pretty dang good. But there are issues I've been wanting to deal with since the first time I hit the trail with it in its current form.

It's currently got a "hot" 3.4l GM v6 making probably 185hp-ish. Trans is the stock Isuzu MUA5 with aftermarket 3.07:1 gears in the tcase. 5.38s in the axles and 35" tires for now. It does fine everywhere but technical crawling - I have to 3 foot it, and beside that annoyance in itself, sometimes I'm worried I'm going to break something, since the throttle is so touchy in low/1st as I'm doing a shitty job trying to feather it through stuff. I'd like to get where I can throw it in low-1st and just concentrate on steering and maybe just 2 pedals.

If I had a diesel with all the torques hitting at idle, it would be fine, but I don't. I think if I had an auto with the same low range, it would probably be fine as well.

I'm not going to drop a diesel in it, but I do have a 700r4 I could use. I could somewhat easily have an adapter made to an isuzu case with the 3:1s. I also have a line on an already set up isuzu dual transfer case unit, or I could do my own (more downtime though).

With the 700r4 + 3.07 case, I'd be at about 50:1 in low + the torque converter factor
With the duals, depending on case ratios, I could be anywhere from ~95:1 to ~130:1 in low/low

I plan to run 37-38's eventually as well.

I like that with the auto, you can work the brake and gas to crawl easier, and you can also wind it out for a bit more wheelspeed while still in low. But I don't like that the swap would be more involved, and I'm also worried that every burnt out vehicle picture I've seen has a story about ATF leaking on exhaust.

The drawback to the duals is that the crawl box case in front has only about a quart capacity and can heat up on the highway pretty quick, although there are some mods and mitigating actions that could be done to help.

Both would require driveshaft changes, but that would be welcomed because currently my front is only about 24" long and binds after about 4" of droop.

What say you folks that have had both type setups?

 

[drkelly]

Your 700R4 plus a D300 with 4:1 gears?

 

[paulevans76]

Your 700R4 plus a D300 with 4:1 gears?

Would be great, but I'm trying to avoid spending another $1000

 

[Jody Treadway]

Would be great, but I'm trying to avoid spending another $1000

You're a bit cornered in that case.
Swap in the 700 and pony up for a custom converter from PTC. That'll be a great aid all the way around

 

[Chris_Keziah]

I'd swap in the 700R4 and use a NP231. If you don't like the gearing the save up and buy an atlas or built 300.

 

[paulevans76]

Sorry should have been more clear. It's a pass side drop, so np231 wouldn't work. 241C could but I don't already have one. I have an extra Isuzu case (stout, gear driven) that I could pop my current 3:1 gear set into. I'm not against a 241 but there would be extra work converting it to fixed yoke, etc.

So, 700r4 with Zu case (or np241), or add the extra case on the back of my current manual trans set up for dual cases?

Have any of you guys run around 50:1 crawl with an auto in a slightly underpowered rig on East coast?

You're a bit cornered in that case.
Swap in the 700 and pony up for a custom converter from PTC. Thall be a great aid all the way around

What kind of stall would I aim for? Stockish, around 2k rpm?

 

[Jody Treadway]

I'm a fan of doublers, especially in underpowered rigs. Best of both worlds IMO.

Regarding the converter, I'd say a 2000-2500 would be a good choice. Enough ooomph to launch, but not so much that crawling becomes chore. Good thing about PTC is they love to offer advice ahead of purchase. Whatever they say, go with it.

 

[paulevans76]

I've definitely heard of PTC so good to know they are respected. I am going to wait a little longer to hear whether the guy is going to actually sell the complete trans+doubler unit or keep it, since that would probably be the easiest, cheapest, and quickest option, before I start spending money on other parts.

Thanks for the opinions. Definitely keep them coming.

I wonder if there are some yota guys who have experience running the stock auto and tcase behind the toyota 3.4 v6, and then converted to or drove one with the manual and duals to compare.

 

[Jody Treadway]

Isn't the 3.4 GM and the 2.5 Jeep the same 60* bellhousing? If so, you should have room for a doubler since the trans would be shorter than the OD 700R4.
Those autos are pretty solid even in stock form and the 23 spline output gives you a ton of options for t case and/or doublers.

 

[Loganwayne]

auto with a doubler. the low low is there if you need it.

 

[Stuntman Autoworks]

I've definitely heard of PTC so good to know they are respected. I am going to wait a little longer to hear whether the guy is going to actually sell the complete trans+doubler unit or keep it, since that would probably be the easiest, cheapest, and quickest option, before I start spending money on other parts.

Thanks for the opinions. Definitely keep them coming.

I wonder if there are some yota guys who have experience running the stock auto and tcase behind the toyota 3.4 v6, and then converted to or drove one with the manual and duals to compare.

I have the 3.4 toyota v6 with 5spd toy/atlas doubler. I love it, I'll be swapping to an auto soon and will be keeping the doubler. Don't know if that helps any.

 

[paulevans76]

Isn't the 3.4 GM and the 2.5 Jeep the same 60* bellhousing? If so, you should have room for a doubler since the trans would be shorter than the OD 700R4.
Those autos are pretty solid even in stock form and the 23 spline output gives you a ton of options for t case and/or doublers.

Yeah, 60* GM pattern, but I do still drive it to and from the trail for now, so I prefer the OD, and the length to be honest. Current isuzu manual trans and case setup is only about 34" long IIRC, and like I mentioned, the front shaft is too short and steep. To alleviate that, I either have to swap to a hi-pinion front ($$$) and still be left undergeared, or swap to a longer trans/case combo, which kills two birds - the steep-short front shaft, and the gearing.

I did look at a 904 and variants, as well as the aw4/a340 and the options they might open up, but it seems like it's 6 of one and half dozen of the other vs the 700r4 options.

auto with a doubler. the low low is there if you need it.

Definitely would be nice, but that's another extra $1500 I don't have laying around for an eco box, or if I'm lucky, just a cool $1k for something used but already set up.

Not trying to be contrarian - I know there are good and better options, but I'm trying to keep it frugal and also not be in project hell through another wheelin' season.

The easiest option for the auto would probably be finding a np241c pass drop right? 2.72:1 ain't that far from 3.07:1 and probably not worth the work to fab the adapter to the Zu case, aside from being "interesting". I could always save up for an eco box + 300 or 205, or atlas to dial it in later on.

I have the 3.4 toyota v6 with 5spd toy/atlas doubler. I love it, I'll be swapping to an auto soon and will be keeping the doubler. Don't know if that helps any.

It does help - it says that I'm not crazy in thinking that a lot of people prefer the control of an automatic.

 

[NickMaul]

I plugged in your numbers to grim jeeper gear calculator and see your crawl ratio is not very far from mine, 62:1 compared to my 69:1

I have enough torque with the 4.0 to only press the clutch in to shift or come to a complete stop while navigating rocks. I really don’t like 1st gear unless I am going up or down a ledge.

I would think duals would solve your issues and not have to mess with a 700R4


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[paulevans76]

I plugged in your numbers to grim jeeper gear calculator and see your crawl ratio is not very far from mine, 62:1 compared to my 69:1

I have enough torque with the 4.0 to only press the clutch in to shift or come to a complete stop while navigating rocks. I really don’t like 1st gear unless I am going up or down a ledge.

I would think duals would solve your issues and not have to mess with a 700R4


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I've spent a lot of time messing around in that gear calculator, and you're right, I'm right at 62:1ish. I'm jealous of that sweet 4 liter torque curve! I can usually crawl through stuff straight on or at a decent grade, but if all 4 corners are trying to do different things and I start steering, she will stall on me, and the throttle is super touchy. I've thought about rigging up a hand throttle so I could set it around 1500 rpm and see how it feels doing that, but I still have the problem with driveshaft length and that limits my madd flexx.

I think either way I go it will be an improvement.