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Discussion Starter · #1 ·
I have a used th350 and th400 both in great shape sitting in my garage. I am currently in the middle of a fiberglass body swap and frame up restoration. I just yanked my old th350 out that was attached to a a NP203 transfer case. Both good transmissions that I have are set up for this full time transfer case, but my friend has a np205...gear driven part time for the th350. What transmission do you guys think I should go with...Off road use is about 40-50%. I currently have 35's, spring over, 350 engine and full size uncut gm drivetrain. thansk for your input.
~TIM~

I'm not afraid of dying...I'm scared of not living

chevy-Cj-7
 
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Discussion Starter · #2 ·
I have a Turbo 350 with Heavy Duty clutch packs and I have had no problems with it. I know the T400 is a beefier unit but I have had my T350 in some pretty crazy stuff and haven't had any problems. I would go with the T350/NP205 combo.

Just my opinion

absolutjeep
http://members.tripod.com/iluvjeeps
 
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Discussion Starter · #3 ·
Just food for thought, a 350 is about 3 inches shorter and has a very slightly lower 1st gear, if either of those are considerations.

Brad (from the 4 Wheeling center of the universe, 4 corners USA)
 
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Discussion Starter · #4 ·
unless you are abusing it(rough wheelin) or are producing major power stick with the 350.
the 400 is a beefier trany but also uses a lot of HP.



CJJ
 
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Discussion Starter · #5 ·
IF your friend has a 205 setup for a TH-350 then that is the one that I would go with. It is smaller than the 203 and is gear driven instead of chain.
Go for the TH-350 & 205.

 

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This is just my opinion, but...
The TH-350 will probably live doing almost anything you can put a jeep through.
The TH-400 really isn't necessary unless you are making more than 400 to 450 honest to god horse power, and able to apply it to the ground.
(Applying 400 HP to the ground is no small feat! Ask any drag racer.)

You may consider the TH-700R-4 also. It is much stronger than the TH-350, and almost as strong as the TH-400, but lighter, gives you an extra gear to keep you in the power band, can be used with or without lockup converter, doesn't waste power like the TH-400, and is something that not every off-roader has.
I saw the adaptors and tail shaft kits for under $200 in two different off road catalogs recently.
Good luck and happy trails.


 

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The TH-400 is definately the HD choice, however; GM always mated TH-350's to small blocks and reserved the big blocks for TH-400's. Jeep happened to choose the TH-400 for various models and years for the extra beef. The 205 xfer is like the TH-400, bullet proof. It's drawback is the puny low range of 1.96:1. The 203 is no better at 2.01:1. With the choices you've listed, I'd go with the 400/205 combo if you can afford the adaptor to mate the two. If not then the 350/205 would be the next choice. Don't go with a small convertor, or the additional heat in the fluid will shorten the life expectancy of the tranny. By the way, the TH-700R4 is comparible to a 4 speed TH-350, not as heavy duty as a TH-400. Where the 700R4 really shines, besides the 30% overdrive, is the lower 1st & 2nd gears compared to both the 350 & 400 trannies.

 
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Discussion Starter · #8 ·
Gonna let everyone in on a little secret here, the TH350 is the toughest choice for a 4x4. The TH700 is not nearly as heavy-duty & the TH400 has ONE major weakness - full-throttle downshifts into 1st gear. Not something that ever happens in a dragster or a towing vehicle, but pretty common for anyone who's ever been stuck in the mud. You've got one & it's an easier fit anyway, so go with the TH350.

TEX

/wwwthreads_images/icons/wink.gif Got Mud?
G.U.M.B.O. Mud Racing
 

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I don't honestly think there's a tranny shop around that say a TH-350 is tougher than a TH-400. That's why you don't find TH-350's behind big block motors. A TH-350 behind a small block motor that's not punched to the limit is a good choice. A TH-400 is better for beef and longevity.

 
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Discussion Starter · #10 ·
Every shop in my area will say exactly what I said. In cases where you'd have to do a full-power downshift into 1st, don't use a TH400 UNLESS you convert it to TH475. Granted, that's limited application, but it certainly applies in the 4x4 world. I have two friends running similar 700-plus HP big-blocks in competition mud bogging. The TH400 goes back for repairs at least once a season - the TH350 has been in there since '95 untouched. We only have two guys I can think of off the top of my head who run deep mud with a TH400, but lots of guys who USED to run one. Granted, what I say may not have anything to do with what the guy who threw up the original post has planned. But, I did qualify my response by saying where the TH400's Achille's heel is. I ran a TH400 in my hot street truck, but a TH350 in my mud racer.

TEX

/wwwthreads_images/icons/wink.gif Got Mud?
G.U.M.B.O. Mud Racing
 

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That is pretty much what I said also, if you have some way to apply 400 Horse Power to the ground, then by all means use the TH-400 (3L80), but if you are going to sling mud (no traction), or you don't produce 400 Horse Power, (99% will not) a TH-350 (3L60) or TH-700R-4 (4L60) will be better suited to the task.
I'm currently testing an AMC 360 CID engine, and when it comes off of the dyno, it's going in front of a 727 TF or a TH-400 (3L80), simply because I have cases for both that match the bell housing bolt pattern.
The ground up rock crawler we are now collecting parts for will have a TH-700R-4 (4L60) because of the optional lower first gear, overdrive, lock-up converter and the TH-700R-4 is only slightly less strong than the TH-400 if the center bearing is replaced with the Corvette/HD/Police ('87 & Up) version.
The first gear shift down you were talking about at full throttle will happen with a TH-400 also, so that argument is moot.
If you don't want the shift down to happen, get a $30.00 Trans-Go shift kit,(Trans-Go! No Yo-Yo!) and install the plug in the valve body to stop the down shift. (They have pictures)

If the problems you spoke of were actual, they wouldn't run TH-700R-4's in (drag) rails.
According to GM's usage guidelines, the 700R-4 is stronger than the TH-400 in all but one category, (shock loading). That's probably why they put them in the Corvettes, Trans Am's, and every other high performance vehicle except the Buick GNX (TH-200-4R) and the SS 454 pick-ups (4L80E, the overdrive electronic shift TH-400), and the first of the SS 454 pickups (Pre '91) had TH-700R-4. 1995 and up 1/2 ton GM 4X4 and some 3/4 ton GM 4X4 trucks have TH-700R-4 (4L60E, electronic shift TH-400).

In case you haven't figured it out, our transmission guy is in the chair next to me. You can do that when you own the shop. (It's good to be King!)
We tow race car trailers to the track every weekend with a 700R-4 at a high rate of speed, race one or more TH-700R-4's every weekend, and are about to off-road one behind a chevy 502 CID that cranks 780 HP on pump gas.
BTW-- A TH-700R-4 has lived in a half a dozen blown big block race cars cranking over 900 HP all season- AGAIN... How do you explain that?

The only draw back I can see in the off road market is the cost of the T-case adaptor and output shaft. (Between $200 and $300)

Note to the extreme user...That much larger bearing I spoke of will fit right in a TH-350 case with no other mods, and increase the trans strength about 15%.
(Low Reverse Sprag/ Center Support Assembly, '87 and newer)
Happy trails folks, Aaron.


 
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Discussion Starter · #12 ·
For reference, the full-throttle downshifts I was referring to are done deliberately by guys with full-manual valve bodies & ratchet shifters. Like when you bog down in 2nd with the tires spinning around 90 MPH (but dropping fast) & ground speed heading for zero. Guys bang the tranny back into first & then bye-bye. It's the one & only scenario where I'd prefer to have a TH350 over the TH400, but it's one that is common in my sport. As to the TH700, properly built, I would have no qualms about using it even in the performance applications you mention. In stock form, I'd toss it out & forget about it. Ditto for the TH400 - it's lone weakness CAN be addressed (we're talking about the - probably spelled wrong - hellical cut gears), at which point it would be my choice. But, that means $$$. And reality is that the TH350 is good enough that spending the $$$ on a TH400 to convert to TH475 (which would be the ultimate in durability) isn't worth it for most guys - especially since extra $$$ for an adapter to the T-case will also probably be necessary. For drag racing, I personally wouldn't use the TH700 because I don't like the gear spacing from 1st to 2nd, but that's a personal preference. I think I'd prefer the 4L80 with a standard 1,2,3 & only a 25% O/D.

TEX

/wwwthreads_images/icons/wink.gif Got Mud?
G.U.M.B.O. Mud Racing
 
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