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Discussion Starter · #1 ·
I have bought a 1974 chev 3/4 ton heavy duty and was wondering besides the 14 bolt rear what the tsfr caser front diff. and trans, probably sm465, were. Any help is appreciated. It has the 4 bolt main 350 in it for a core. The gears are probably 3.73 or 4.10 right?? Thanks for any help!!!! ;) ;) ;)
 

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Should be an NP205 unless it is a fulltime unit (203)

Manual tranny will be the SM465, Auto TH350 or 400??

What's the GVW??

Front axle will be D44, rear 14FF.

Ratio is stamped on a tag hanging off one of the lower bolts on the front diff cover.

Correct, either 3.73's or 4.10's.

Look for three bolts on the intermediate shaft cover on the rear of the t-case to identify it as a 205.
 

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Discussion Starter · #3 ·
Ok. So it will for sure be the sm465. It is a fulltime so is it for sure a 203 and is the 203 any good?? I will check the GVW but there is no tag on the axles front or rear. Thanks ;) ;)
 

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yep manual will be 465, they stopped using SM420's in 73.

To double check look for a casting number on the passenger side that is xxx365 or something like that.

There's also a couple sm465 pics in my webshots i think if you're interested.

NP203 is supposably a pretty strong, and pretty heavy unit.. drawbacks is the full time nature of it.

SHould be really easy to swap an np205 in if you don't like the 203.
 

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Discussion Starter · #5 ·
The GVW is 7500 front is 3500 and rear is 4880. I have been told the rear is the larger 10.5 ringgear 14 bolt and the tag I found on the axle reads 45-11 and 4.09 so that is 4.10's correct???
 

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Discussion Starter · #9 ·
So do you think 500.00 bucks was a fair deal on my end?? It was a complete truck with a bad wrist pin. Both driveshafts andthe body has little rust. Less than my 83' does for sure. It was the farms water truck so the mileage is low. All I need is some 16. 16.5, or 17 inch rims and I am set!!!! Thanks for the help.:D :D :D :D :D :D :D :D :D :D
 

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Discussion Starter · #11 ·
It has the 13 inch disc's and a friend here can posibly get me some rims through his work for 15% over cost!!! so 16 or 16.5 it is. I am running 36 12.5 15 super swampers now and they look a touch small so I would like to move into 37's. The detriot locker in the rear of my 83 just about is shattered so this deal came in good time. The 83 will be parted out now.
 

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You should look for a NP205 if you plan on actually using your truck, the 203 behind a std. was one of GM's worst combo's. The std. tranny had a reputation of breaking chains and other parts in the 203's, since there was nothing to take up the slack in the drivetrain (ie. torque convertor). An option for you is to find a 205 and use your 203 reduction box with a doubler kit, to help overcome the pathatic low range in either box.
Steve.
 

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The 203 uses a gear drive reduction for low range, which is very strong. The front and rear outputs are connected through the chain case (middle section). The differential is in the rear section, which can be locked and unlocked for street or off-road driving. The 203 was a decent t-case as long as they were maintained (proper oil used 10W30 or 10W40) and the chain was replaced when needed. The problems with them were weight (very heavy), and on my old one engaging and disengaging 4-Loc. The reason I said it was a bad combo behind the std. tranny is that positive engagment of gears in the std. causes shock loading on the chain which in turn causes breakage. The auto trannies weren't as hard on the 203's due to the smoother shifting patterns.
Hope this helps you, Steve.
 

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No the 203 was chain driven. I had one in my 79 Sburban. It has a light aluminum case and it is no slouch but it is no where near as strong as the NP205. Many of the guys with 80's and 90's trucks are retro fitting their rigs with 205s because of their strength and longevity. If you hook your 203 behind a 205 you will definitely be able to crawl!!!

Rod;)
 

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Actually you put the 203 reduction box in front of the 205. Makes a heavy-duty version of the Marlin Crawler. Also the case on a 203 is cast iron, the only alum. parts were the bearing retainers and the differential housing. The first all alum. T-case was the np208 which came out in '81 if I remember correctly.
 

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Discussion Starter · #20 ·
Yes it is all cast iron. A real brute!!! Where od I get the info about the setup you described??? I have a 205 as well that looks real lonely............hehe
 
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