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2wd tranny in a 4wd rig??? Can it be done?

J

Jessejames

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I was told today that a long tail trany from a two wheel drive can be modified to fit into my transfer case. If the tranny tail piece is removed and the out put is cut to proper length. Is this sound advice? Has anyone done it? My uncle said he had done it but that was many beers ago! So I'm a little Leary of trying it. I have an 81 k5 with three speed set up. But it's out of a 79. The original tranny got smoked by former owner. And the trany he had wouldn't hook up to the transfer case of the original. So he put the 79 setup into it. I have both set ups Now and all the drive shafts and am lookin to find a tranny that will drop in. PLEASE HELP
 
What transmission? TH350 or TH400 (both are 3 spds)? If you're unsure of which it is, post a pic or description of the shape of the pan. Also, measure approx how much tailshaft will be sticking out once the tail cone is removed (different models have varying lengths).

If you're working with a 2wd transmission that has the really long tailshaft (approx 12") I doubt it's splined long enough to trim it down and have enough spline left.
 
I will get some pics up ASAP. I just picked it up
Today. The reason I asked is I've found a two and a four wheel drive tranny. The four is quite a bit more cash and if All I have to do IS cut down the out put its totally worh it. From What my uncle said he's still drivin his truck with this fix and it's seven years later. Just curious if any one here had done it this way.
 
Brett has some info on tailshafts as well, some can be cut down to work...
 
A 2wd th350 should be able to be cut down enough to run a np208, maybe with a spacer though. I doubt it could be cut down enough to run the np203.
 
i cut down my th350 2wd to work with a np241 with a 2 " spacer from advance adapters as a temporary deal and it worked just fine. no idea on any other applications except that it will no way work with a np205.
 
Yes It is possible,but only with some mods or adapter/spacer blocks...they sell a spacer that allows a 2wd truck or car TH350 to replace a 700R4 ,you need a TH350 with the 6" tailshaft housing,which is removed,and some of the output shaft must be cut off in order to get the proper length--the spacer allows the TH350 to be the same length overall as a 700R4 so no other mods are needed to the drive shafts,etc.........some (as in very few) Th400's with short tailshafts from 2wd's or cars will couple to a few T-cases like the Np-208 with no mods,I have heard of some owners having a custom built adapter made to bolt up a TH400 with a output shaft a bit longer than the proper 4x4 version,but that entails driveshafts modifications as far as length,relocating the crossmember,etc....................................................................................................I've seen a few lifted GM's (ridiculously high lifts !) with a 2wd automatic tranny,no transfer case,just to allow it to be used during the summer months ,no more 4x4 capeability...which is probably my last choice!--be better than walking,but would make a truck used for off roading or plowing pretty useless..I wish GM just stuck with divorced transfer cases,then ANY tranny could be swapped in pretty easily...why they have so many different output shaft lengths,spline counts,t-case adapters,and a specific "4x4" tranny,baffles me--you'd think it would have been much cheaper for them to just use the same design tranny in everything,instead of having to tool up to build 20 different ones...
 
Yeah, divorced transfer cases make a lot of sense in long wheelbase trucks. Helps distribute the weight and gives nice front drivline angles as well. They would have to weigh the cost of an additional crossmember (or 2) and additional (short) driveline against the savings of common parts. However, when you're talking about a K5 wheelbase, smashing the whole drivetrain into a single package looks more attractive.

So a 2WD tranny can be used with a divorced case just by making the right length driveline, I assume.
 
You can use the case no problem from older 3 speeds. Mine is a 2wd case as 4wd TH400 cases around here are not as common as they used to be. The case difference between 2 and 4wd is usually just some extra ribbing on the tailshaft area to make the area where you mount a t-case stronger. The output shaft is the main difference.
 
diesel4me said:
Yes It is possible,but only with some mods or adapter/spacer blocks...they sell a spacer that allows a 2wd truck or car TH350 to replace a 700R4 ,you need a TH350 with the 6" tailshaft housing,which is removed,and some of the output shaft must be cut off in order to get the proper length--the spacer allows the TH350 to be the same length overall as a 700R4 so no other mods are needed to the drive shafts,etc.........some (as in very few) Th400's with short tailshafts from 2wd's or cars will couple to a few T-cases like the Np-208 with no mods,I have heard of some owners having a custom built adapter made to bolt up a TH400 with a output shaft a bit longer than the proper 4x4 version,but that entails driveshafts modifications as far as length,relocating the crossmember,etc....................................................................................................I've seen a few lifted GM's (ridiculously high lifts !) with a 2wd automatic tranny,no transfer case,just to allow it to be used during the summer months ,no more 4x4 capeability...which is probably my last choice!--be better than walking,but would make a truck used for off roading or plowing pretty useless..I wish GM just stuck with divorced transfer cases,then ANY tranny could be swapped in pretty easily...why they have so many different output shaft lengths,spline counts,t-case adapters,and a specific "4x4" tranny,baffles me--you'd think it would have been much cheaper for them to just use the same design tranny in everything,instead of having to tool up to build 20 different ones...
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While this is all true, atleast Chevy sticks with one bellhousing bolt pattery and a pretty simple array of spine counts and so on. Imagine Ford lovers problems with several bellhousing patterns, several motor options, and several more spline counts, thats a mess if I have ever seen one.
 
Thank you all. My goal is to be able to plow this winter and start building it for daily diver in the summer months. I have no garage. So I'm doing this all in an empty lot. I have two transfer cases for it. The original and the one that's in it now. I will get the numbers and hopefully be able to get some idea what I'm workin with. Also I have two smoked trannys. What should I do with them? Junk them or... Again thanks to All.
 
Thank you all. My goal is to be able to plow this winter and start building it for daily diver in the summer months. I have no garage. So I'm doing this all in an empty lot. I have two transfer cases for it. The original and the one that's in it now. I will get the numbers and hopefully be able to get some idea what I'm workin with. Also I have two smoked trannys. What should I do with them? Junk them or... Again thanks to All.
 
Also I have two smoked trannys. What should I do with them?
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Well, the holiday season is coming up. Clean and polish them up well, and they would make very unique Christmas gifts.
Bet they would not already have one....
Some people give smoked hams, some give smoked turkeys..................
 
I agree with the comments about the Fords being "worse"....as far as having way too many things different,even on the same year trucks!..I hated it when I had to ask for a production date if the listings were different,none of the owners ever knew it ,or where to look,and sounded disgusted when I asked,like I was just being a nutcracker...you NEED to know when it was built...(0n some parts I bet they needed to know WHO put the truck together probably!:doah:.....).............................................................................As for the smoked trannys,if the cases aren't cracked I'd see if a core supplier or transmission shop would pay anything for rebuildable cores before scrapping them--like they say,they aint making any more of them,and they are getting harder to come by,especially here where everything rotted away and was scrapped long ago....................................................................................................Divorced T-cases are the berries as far as I'm concerned--yeah,in a K5 there really aint enough room to use one easily,but on a full sized puckup there is plenty of space for a short driveshaft...I like the fact you can stuff anything automatic or standard in front of a divorced t-case just by making a short driveshaft with the correct yokes and u-joints to mate to the tranny output shaft and the t-cases input...anything from a Powergide to a M-22 Muncie,or a SM 465,just about any tranny GM used would be adaptable ...
 
I dont see any reason why it wont last as long as any factory installed TH350 would,provided the splines have sufficient engaugement,etc...if it was a high mileage tranny to begin with,then yeah,it might fail early under hard abuse,but otherwise I doubt it....the "K" case is somewhat stronger,but I've had 2 trucks with car tranny's in them and no "strut" rods to the belhousing and haven't busted either of them up ...(yet!)..:rolleyes:
 
Well i aprecitae the come backs. In what way can identify the trnsfer cases. I have two and all the drive axles for both trannys that were in it. So all I have to do is find a tranny like one of the two and I should be OK. I stil haven budgeted the time to go wrench on my little project, like I said before I'm not gona build a show vehicle. Mainley this will be plowing and fire wood buggy. I think I may loose the cap and build a wall and head ache rack and make a short wheeled woods buggy out of it. Something legal but nasty.
 
Probably the easiest way to I.D. a T-case (if there is no tag on it !) ,would be to google the one in question under "Images" and you'll likely find photos of one..most GM T-cases had a tag riveted to the front of the case,facing the front driveshaft,that has the type and gear ratio on it--it will say something like "NP-205"..."Ratio 1.96"...usually has a date of production stamped into it also...
 
diesel4me said:
Probably the easiest way to I.D. a T-case (if there is no tag on it !) ,would be to google the one in question under "Images" and you'll likely find photos of one..most GM T-cases had a tag riveted to the front of the case,facing the front driveshaft,that has the type and gear ratio on it--it will say something like "NP-205"..."Ratio 1.96"...usually has a date of production stamped into it also...
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all mine have had the tag on the rear :whistle:
 
The old NP-205's I had (1972 vintage or thereabouts) had the tag facing forward ,above the front driveshaft...newer T-cases like the NP-208's in my 80's trucks have the tag facing the rear end....there should be one somewhere on it no matter what year or model it is!..if the tag is missing,photo I.D. is the only way to tell what one it is...
 
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