Attn 4x4 Guru's

[Stano]

I have decided to build me a 4x4 for a daily driver/winter vehicle. I have a solid 74 1/2 ton frame that I am gonna use and I have a 84 K-5 blazer that has a rotten body and good drivetrain and enough rust free body parts to build a longbed truck. My question is will a 700R4 bolt to a NP205? Or would I be better off money wise and time wise to just use the 350,700R4,NP203 setup straight out of the blazer. What will I have to modify on the 74 frame to accept the blazer combo? I am on time and money constraints like most of us so I am not looking on spending lots of $$$$ to get this thing together and running. I know alot about these trucks and 67-72's but not messed with the 4x4's much other than maintenance on the blazer and my folk's suburban I am kinda dumb in the transfer case and tranny interchange area. So if any of you folks can give some sound advice I would greatly appreciate it and so will my wife who has to put up with me and my truck habit. LOL

[*MJF*]

I am by no means an expert, but to mount a 205 in place of the 203, you will most likely have to buy an adapter. Advanced adapters sells adapters to mate almost anything together, but they are expensive(cheapest being around $300).

To mount the 700R, you will probably need the crossmember & will have to drill new holes to mount it under the frame. The 700R is longer than a TH350. You will most likely have to lengthen or shorten driveshafts depending on what vehicles the ones you use came out of.

There's probably some other things I'm forgetting. I have to be there & see it before I can figure all of it out.

[*MJF*]

Also I think alot of the 203's were full time cases. Most people try to convert them to part time but I think it's a little expensive too. Someone else can shed some light on this. Or they'll raise the flag & tell me to shut up cause I don't know what I'm talking about.

[1969 GMC]

i am about 99% sure that all 203's were full time (unless converted by the aforementioned kit). they are big heavy cast iron like the 205, but a little less strong. i have heard that with the kit, they sometimes crap out unusually quick, something to do with one of the bearings not getting needed oil while in 2 wd. i have heard someone (pretty sure on this board) say that every time they fill up, they lock it into 4 hi or 4 lo and drive a while to lube the inside of the case good. i would say just leave it full time, it doesn't sound like you do extreme offroading (read: competition rockcrawling) so the 203 will be ok. you already have OD with the 700r4, so that's good. i'd say you will be fine.

[Mudder]

I have converted 203's to part time and never had any problems. Some 203's behind 4speeds were part time from the factory. 203's are a dime a doozen around here Stano. I bought my last one about 10 years ago and paid 60 bucks for it. No, its not used a lot but it does work when I need it.

[JIMs70GMC]

I think it should be a NP208 in the 84 K5. Behind the 700R4.

[Mudder]

Stano met one of the guys you work with Sunday. He gave me a flyer for the show over there. I will try to make it but told him to have you remind me a week or so before.

[*MJF*]

So if you leave a 203 full time, do you need to use the automatic locking hubs or can it be changes to the manual hubs?

[Mudder]

If you leave a 203 full time you need to have the full time hubs. If you make it part time you will need the manual hubs. I have never messed with automatics. Had them on a 86 Blazer one time and I replaced them with manuals.

[Stano]

Ok Jims70 you are correct! I haven't been under the ol blazer tag huntin for a while and NP203 sounded right to me but IT IS a NP208. So my question still stands the same about the swap. Pointers or advice is all appreciated.

Mudder, Kirk told me he met you said you seemed like a pretty good fella. LOL Hope to see you at the show in August it is a pretty nice show get there early so you can get a shady spot under the trees.

[MAC67]

yeah i to think all 203's or atleast im 9999999% positive,, you can get like a doug nash parttime kit ,, but id save my dough and opt for the 205 adapter,, and jim is more than likley coorect,, youre 84 should have had the aluminum case chain box 208,, go the 205,, less headaches and more stout

[DrMaserati]

Originally posted by Mudder67
Some 203's behind 4speeds were part time from the factory.

The NP203 is a full time case, period. Not most of them, ALL of them. The NP203 was not used behind manual transmissions, only automatics. The manuals of that vintage used the NP205, and later models went to the NP208.

I run a converted NP203 behind a 454. I had it converted with a Doug Nash shaft in 1986, and I have yet to break anything. I'm sure the argument will go on forever about which is stronger, the 203 or the 205, and there will never be a concrete answer or agreement on the issue. But in the real world there isn't enough difference to worry about.

JP

[JIMs70GMC]

The 203 was mated to the SM465. It was the worst combo, too. Unless of course your going to use a doubler from ORD.

[Mudder]

We learn everyday!

[MAC67]

205 is stronger,, always wil be without a doubt,,the only advantage the 203 has over the 205 is the lower ratio

[1969 GMC]

the 203 is heavier than the 205...alot heavier. i think its close to 200lbs, and the 205 is something like 115. just something to think about.

[76bonanza]

Hey stano just noticed you live in rolla I am just down the road in st robert.

[Stano]

hey 76bonanza. yup not too far away. mudder67 is in owensville and there are a few other local boys too!


This is a low budget build and i do mean low so i won't be buying any adapters or anything. just wanting to know if what i have will work or not. prolly just put the 350/700R4/208 combo in since i got it and its all good. i priced a reman TH350 to mate to the 205 bit its outta my price range right now too. LOL So when the 700r craps out i will then put in the 350/205.

Now what did i do with all those crossmembers bolds, and brackets LOL

[drink2mny]

I'll tell ya what i run..'86 fullsize blazer
476bbc 700r4/np208.. 1 ton running gear. dana 60 up front 14 bolt in rear. i run 36's on some days and 38's on others..
I hit a lot of the local mud races around spokane wa..

I was daily driving this rig for awhile till i hit the jackpot on a 2wd 72 super cheyenne for a daily driver..

I have yet to have a problem with the tranmission transfercase combo..very nice fist gear ratio in 4 low..
I have jumped this rig and off road it almost every weekend..
I do however have a 205 and adaptor ready to bolt up just in case i break the chain in the 208..but the 205 definatley is bulletproof with gears instead of a chain in it.i have seen them hold 3500 stall drops at the races..
i would never recomend the 203 unless you need an anchor.it is still a chain drive also.

If you want a 205 to 700r4 combo you don't nee to call advance adaptors all you need is an adaptor from a t350/205 combo with you can also buy at a gm parts house..
When i get the adaptors i sell them for 250..
which i do have an extra one



Here is a pic of my blazer
check out my buddies business webpage below in my signature

[Stano]

Good news for me that is. LOL I scored a reman TH350 with a little work done to it and another 205. My buddies dad has (or should i say had) a 79 burb that got wrecked a while back and he decided not to fix it so he yanked out the motor and left the rest for the vultures. It has 3.42? gears Detroit Locker in the rear complete front end and suspension. Gave it to me for some body work I did for him and he needs a fender fixed on his Vette. So I am happy and I won't have to deal with the 700R4 swap now. Thank you all for your information and advice. It is much appreciated. I will prolly have more ?'s for the 4x4 Guru's in the future.
Stan