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post #1 of (permalink) Old 09-23-2003, 01:51 PM
**DONOTDELETE**
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drivetrain help

Hi, I have an 82 gmc jimmy full size, with a 350, th350 transmission with lockout, and not sure of the x-fer case, but i know it uses belts and drops to the passenger side. The rest of the truck is pretty much standard equipment. Now my question is. The transmission just cut out on me, i want to get a better x-fer case (like np205 gear driven i believe). should i repair my th350 with lock out? I am using my truck as a daily driver and a mudder, I recently (last year) put a four inch lift and exchanged my 31" tires for 33". I really want a strong drivetrain and put my 350 to work, but I dont know where to begin. Please help me. Any suggestions would be wonderfull.
thanks,

john m.
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post #2 of (permalink) Old 09-23-2003, 04:16 PM
Resurrection_Joe
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Re: drivetrain help

Hrmahhh... yeah, I'll try and help. There's a lot of room to interject opinion here, but I'll try and stay unbiased.

First, all GM cases up to 87/91 dropped passenger side

Belts? Maybe chains, I have never heard of a belt drive t case on anything

With a 1982 I'd bet 99% it's a NP208

Now here's my thoughts -

If you don't plan on getting super large tires and beating the [bleep] out of your truck, I'd keep the 208. If you stay 37" tire and under and donít plan on swapping axles in and out, it should be fine.

The TH400/NP205 combo is very strong, but it has a 2.0 low range and the tranny is rumored to suck a lot of power compared to other autos

A TH350/NP205 combo would be good too, but an NP205 is heavy and again only has 2.0 low. On the plus side, it does have a fixed yoke if not made in 1980 and is beefy

The TH350/NP208 combo you have now is strong enough for what I think you're going to use it for and has a lower low range at 2.61, but it does have some drawbacks. The 208 is aluminum and hangs lower. It usually has a slip yoke, which isn't all that desirable for quite a few reasons, driveshaft balancing and fitment and the ability to take the rear shaft off without puking all the fluid out come to mind.

So you have various options here. A TH400 would be beefy, but a TH350 isn't going to rollover and die like a 700R4. Also, TH400 are more expensive and getting harder to find, but just about the same price to rebuild as a TH350. A TH350 rebuild or rebuilt tranny is VERY cheap compared to a 700R rebuild with the right parts.

NP208's may not be the ultimate in durability and the slip yoke is kind of annoying, but you can get a SYE (slip yoke eliminator) kit to remedy that. Plus, you get a lower low range, a lighter case, and replacement cases are dirt cheap. I have one in my shop I'd sell for $100 or so. It does hang down a bit lower though, and that can be a consideration if you ever want to be running drivetrain bashing trails.

An NP205 is, as I've said, a rocksolid case, but heavy and lacks a decent low range. It is also slightly harder to find these days.

I never mentioned an NP203. It's a full time case and not really a good swap option. I have one in my K5 and like it fine, but I'd never wanna put a standalone NP203 into anything I had options with. If I have one in the truck though, it's fine with me.

So in summation, I say go get your tranny rebuilt or find a new one. I've heard of great rebuilds for $400 - $600. The TH350 is a damn good transmission and swapped into many vehicles around the off road world. It also can stand up to some abuse in the big ass trucks we tend to build.

Your other option is shopping around for a matched set (Tranny/Case) or putting a new case behind your TH350. Any swapping of cases you do is going to need an adapter. They are expensive. I know.

I had a situation kind of like yours a while ago, blew up a 700R4/NP208 combo (well just the tranny). I was going to put a rebuilt TH350 in front of the np208, and kind of regret not doing that to this day, but the tranny guy, who was an off road dude, sold me a TH400/NP205 combo out of his parts truck, and installed in with a quick inspection. I love the combo, and the low range is good enough, but the tranny is nasty looking and has a leak, and I think I may just have to have it gone through soon. I think there's a shop relatively near here who will go through it for $400 and guarantee their work for a while.


Hope this helps

Shane Wager / Resurrection Joe
post #3 of (permalink) Old 09-23-2003, 09:03 PM
 
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Re: drivetrain help

I would say you nailed it
the only one you didn't say was the four speed.sm465
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post #4 of (permalink) Old 09-23-2003, 09:33 PM
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Re: drivetrain help

Yeah I assumed he wanted to keep an automatic..

SM465/(case) Combos are varied with whatever case is behind them. The 465 is pretty much bombproof, but the clutches can go out on you, and you have to shift, so whatever
post #5 of (permalink) Old 09-23-2003, 09:41 PM
 
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Re: drivetrain help

"The 465 is pretty much bombproof"
the only chatch is they like to eat third.I am on my third and thrid is going out of it. But the did have all the oldre cases.
"and you have to shift, so whatever"
Just put in thrid and stand on it
do you chatch a trend


On a side note if we keep posting like this the board might come back to life
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post #6 of (permalink) Old 09-23-2003, 10:59 PM
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Re: drivetrain help

Yeah, I'm not to up on SM465 info

Do you mean 3rd 1:1 or 3rd actual 3rd position ?

3rd and stand on it? My pokey 355 would go "Oh for ****s sake" *clooomph*
post #7 of (permalink) Old 09-23-2003, 11:02 PM
 
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Re: drivetrain help

Do you mean 3rd 1:1 or 3rd actual 3rd position
3rd position
get a real big motor and try theres times mine struggles ith it
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post #8 of (permalink) Old 09-24-2003, 05:56 PM
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Re: drivetrain help

Hey,
Awesome reply, Shane. As you can see im new at this.
You have helped me put myself back on track. It seems i'll keep the th350 and maybe get a new torque converter. as far as the x-fer case the guy who rebuilt it for me, told me it had belts...??? so i have no idea. Since my x-fer case was rebuilt last year I'll just hold onto it too. Now i have a new question, if you see this, do all th350s have this (lock out) thing? my impression of it is that it helps bring the transmission to a 1:1 ratio with the engine, when on the highway. Is the lock out a good thing or a bad thing?
can i change my transmission from lock out to no lock out? the reason for my questions are that i was told lock out over heats a transmission. one more time fellas, thanks.
john m.

post #9 of (permalink) Old 09-24-2003, 06:33 PM
Resurrection_Joe
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Re: drivetrain help

I assume what your talking about is a lock up torque converter.

I don't know much anything about them, I ASSUME it locks to direct drive with no slippage or something.

Seeing as I don't knbow much about this I'll do a search...

Here's Something

Here's Something Else

What I can infer from these quick searches, and this is just a guess, is that when you have a non lockup torque converter, the engine spins the converter faster than the tranny or something, and when it locks up it's direct drive and they match speeds so you can cruise at a lower RPM

Looks like they make the drivetrain a bit weaker...

I dunno, Jason or someone will come along shortly to explain it to both of us.

Oh, and belts can be easily confused for chains

Glad I could help! Stick aorund, we wanna give this forum life!

post #10 of (permalink) Old 09-24-2003, 07:25 PM
 
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Re: drivetrain help

Ok, here we go...

The torque converter has a turbine and an impeller. In a non-lockup converter when cruising and the converter is hydraulically coupled they are usually within 90% of each other in speed. This is where about 10% of the engines power is lost and it also causes heat in the transmission. The lockup converter locks the turbine and impeller. It usually takes place around 40mph but there are a few things that can stop this such as the engine not being to full operating temperture, not being in OD or whatever the top gear is, under heavy acceleration, etc. So the point is you don't lose that 10% of power and you don't get the heat that comes with it.

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