TH350 or TH400?

I'm switching my 3-speed Jeepster Commando to an Auto. Can't decide on a TH400 or a TH350. I have the 225 V6.

I've read that the TH400 takes 45 HP to operate versus 30 for the TH350 so using the TH350 gains 15 HP over the TH400.

Problem is, the TH400 was the stock auto for the Commando, and its easier and cheaper to go with the 400.

Does anyone know if there is a noticable performance difference in using the TH350 over the TH400?

 

Turbo 400, bulletproof.

 

you've answered your own question

why do you want the auto trans ?

The T350 is mostly used in CJs where length is a concern

 

Find an automatic partster and go TH400. Stronger than the TH350 and all the installation issues have been worked out for you. Buick 300/340/350 is a ridiculously easy swap if you want to make back that 15 horses (and more) cheaply. Plus, with the TH350 you'll have to buy an aftermarket adapter, while the TH400 can be done with junkyard parts. Much less expensive.

But you knew that

 

http://www.oldengine.org/unfaq/leadfoot/trans.htm IIRC 70 'bout right on the TH400

 

I found the HP info from a number of different places, but most recently from www.442.com

http://www.442.com/oldsfaq/oftrn.htm#Transmissions

I want to stick with the 225. Maybe it's sentiment because that's what I had in high school, but it's also a great engine and it's (in my mind) what Commandos are all about. Yes, there are some L-4s out there, and the Bullnoses, but the name of this website "The Early CJ-5 and Dauntless V6 Page" says it all.

I'm having the engine rebuilt, and it will be slightly bored, but my wife will be driving it occasionally so I want it to run well and I dont want to mess with the intake and carb, so I'm not going to do too much to the engine as far as cams and exhaust go. I don't expect it to go much over 180HP, if that.

Consequently, I want as much driveline efficiency as I can get, and if I can gain (or save) 15 HP, and if 15 hp is noticable, it would be worth the expense of going with the 350 rather than the 400.

I had planned on using a Novak or Advanced Adapters kit with either transmission because I have read (on their sites) that the stock adapter is weak and prone to breakage. Is this true? If not, then that does weigh in favor of the 400.

Thanks for your time

BW

 

The adapters do break, more so if you're doing more hardcore off roading than just driving around town. My 73 is still running the one it came with. I don't do any hard core but lets just say I don't baby it either. What they are prone to is corrosion at the holes for the mount.
If you do go the 350 you'll also need to rig up a kickdown cable to the carb. I've driven a few V6 Commando's with the 400 turbo. Can't really say an extra 15hp is going to make a whole lot of difference although every little bit helps I guess. If you figure your rebuilt is going to be cranking 180hp that's 20 more than stock so you're 5hp in the good if you go with the 400.

 

I have been thinking of this thread all day, I read it this a.m. and I wanted to respond with a book. But to make it short, I would stick with the TH400. If you're worried about the 35HP loss, then go to an underdrive pulley system, go with a modern grind cam, electronic ignition, bump up the compression if you decide to build the motor. All of these will give you back your 35HP plus.
Just my $.02 worth.

 

Seems like going with the 400 is the popular choice.

From what I've read, the TH400/Dana 20 combo from any Jeep, including the Wagoneers and the Pickups will work. They're all the Chevy housing so I need the adapter.

I underestand the flexplate from and odd-fire 231 will work, up to '76 if I recall.

Question about the flexplate. Does it have to be balanced or does the torque converter take care of this?

Finally, what about the NP205/203s out of a GM P/U?

 

Don't get an NP203...they're huge, weigh a ton, and are chain driven. The NP205 is a great gear driven transfer case, but probably way overkill for a V6. Both are center output to the rear, and both can be connected to the output of a TH400 with the correct adapter & sleeve. The 203 was used in "full time" 4wd applications for GM trucks, and the 205 was part time (with hub lockouts). I'm sure others will weigh in, but unless you were doing a V8 conversion, I don't know that I'd bother with either since you'd have probably have to go with custom drivelines to do the swap ($$). The transfer case itself can be had pretty cheap from a junkyard...around here you can't give an NP203 away. 205s go for a few bucks though. The adapters seem to be worth more than the transfer cases :? .

 

Wagoneers and Pickups up until 73 and some early 74 used the same combo as Jeepster and Commando. After mid 74 they went to the AMC bolt pattern case without an adapter but the output shaft was also changed. The tranny bolt pattern is Buick nailhead and you will need a BOP adapter but they're still pretty easy to get a hold of since every Jeepster with a V6/auto used them and the old Gladiator/Wagoneer with the 350 Buick/auto trans option used the same adapter.
As to your flexplate question I can't really say 100% that an early 231 odd fire would or wouldn't work but I suspect they might. If you check with a local GM dealer parts department they might be able to still cross reference the part number. There are still 225 flexplates out there, I got one off Ebay a year or so ago. Can't remember off hand how they're balanced but it's not through the convertor as they're pretty much all the same.

 

I've been running 400's behind buicks for years and love the combo. My current daily driver is a 3-b with a 231/400/20 combo, 3.73s. Drives as good as any Jeep I've driven, never had a problem with it.

 

I'll kick in my .02...

The TH400 was stock, and is stronger than the TH350. Strength shouldn't be an issue with a 225 and tires under 35". If you can find a partster, all the homework is done for you, it's basically plug and play.

But- On my Jeepster I went with a TH350. Had a TH400/D20, but I wanted to use a D300 transfer case. And you can make a cheap homebrew adapter for under $200.00 I used a TCI adapter plate from the Buick block to the Chev trans case. TH350's did come with buick direct bolt up cases also. If you chose this route, driveshaft to trans pan clearance is minimal without a 3"+ lift. My main reasoning for this set up was the slightly lower 1st in the TH350 along with the 2.61 low range of the D300. (I had them both lying in the shop too... that helped!)

 

Sorry to hijack the thread but just a quick question.
Doesn't that make a really short rear driveshaft? Any problems with it?
Keith