TH400 In A '72

[special-K]

I got a hold of a TH400/NP205 combo I want to swap into my '72 K2500 and have some questions. The only swaps I've done on 67-72s were using parts from withing the era. I haven't actually picked the unit up and want to know,since the guy is removing it this weekend,what other parts I should grab to make this as easy as possible. My '72 is all factory 350/TH350/NP205 Dana44/Dana60 Power-Lok drivetrain. I actually prefer the shifting points of a TH350 over the TH400,but the plan is to build the truck beefier than stock. It's going from stock to 383/TH400/NP205 Dana60/HO52 No-Spin. Can I use my transmission linkage,crossmember,and just straight swap? The donor truck is a 454,so I can't use that torque convertor.

[OLDCHEV4X4]

Hey Tim, I have some of the parts to do the same swap too. And my 85 1 ton has this set up. The front output on the TC is a flat flange, so front drive shaft is needed. The rear ouput on the TC is a slip yoke, so rear drive shaft is needed.
kick down switch on the pedal or the intake is needed. Dont know about the crossmember or linkage.

[Ol Blue K20]

You might be able to swap the front output yokes (if splines are the same) should be able to use stock crossmember as trans mounts are on the 205. I don't know if the holes are in the frame might have to drill some because I think you'll be moving back some. shift linkage I believe is the same. You will need to add kick down switch & harness.

[Ol Blue K20]

I forgot to mention you might be able to use torque converter, most flex plates are drilled with both small & large bolt patterns

[OLDCHEV4X4]

Originally Posted by Ol Blue K20

You might be able to swap the front output yokes (if splines are the same)

Front output spline on the th400 NP205's are a fine spline and are stronger than the older 10 spline 205's.

[Ol Blue K20]

Originally Posted by OLDCHEV4X4

Front output spline on the th400 NP205's are a fine spline and are stronger than the older 10 spline 205's.

Well so much for that idea...gotta luv this board I learn something everyday... thanks

[special-K]

Ok,thanks. So,I can use the driveshafts from my '91 Suburban that had a 4L80E/NP241 if he doesn't give my his driveshaft? Not too excited about the TC rear output slip yoke. Never thought about that. Gotta look into eliminating that. I knew about the electric kick-down,but never thought about the truck being TBI. O may need something there. I'll go look this Sunday and see what's what. Kinda hard to figure without everything here. Randy,I guess this truck's the same set-up as yours,except for TBI 454

[BLAZERMAN]

I've done this same swap several times, just to add a few things.. get the gas pedal assembly from a 71/72 that had a TH400 that way you'll have your kick down switch and grab the wiring harness too. Your crossmember will work but you will have to drill the frame a few inches back..linkage will hook right up. Its not a must but I recommend buying an SFI approved flexplate, they are thicker and double welded..only run about 70 bucks for a B&M or TCI.

[special-K]

Thanks,Rob,for more solid info. That makes sense to nab the pedal/cable/harness from the same body truck. I said my reason for doing this is to go "beefy" so a stronger flex-plate is on the plan. Since I'm going 383 I plan to get the Scat external balance flex-plate and balancer.

I drove the truck yesterday (first time this year) and it reminded me how "just fine" the TH350 performs and has performed all long. The truck has a 5th wheel set-up from the original owner and a big trans-cooler. The truck has 235/85s and when I put the pedal to the metal I get a little a skirch catching second. It's a strong & tight li'l TH350. I've never had one not do what I threw at it. It's a strong li'l 350,for that matter. But,I just gotta grab this late NP205/TH400 combo,even if I don't use it in this truck. I originally thought I'd use the 4L80E with that 205,but decided I'm fine with no O/D AND no computer in this truck.
Who knows...I change my mind a lot. It's hard having just the one truck. My philosophy has always been "Don't decide. Just have enough trucks to do all the different ways I like". I'm new to this just one truck thing. When I had the two '72 K/20s,this '72 K2500,and the '71 K/10 SWB I had it all covered. One for a work truck (Highlander Custom Camper 4spd),one for a highly optioned minty gem (Cheyenne Super Custom Camper TH350),one for an RV travel machine w/4Wheel Camper (Sierra Custom Camper 4L80E),and one for badass 1t play toy (Custom Deluxe SWB Stepside 4spd) that was going to appear as a '69 GMC Super Custom. Oh yeah,and the li'l 2wd hot rod street truck (327/M22). Now it's one big 4wd and one little 2wd. I also toy with maybe taking the NV4500 from my '92,if I can get a truck to replace it,and hook that up to this NP205 for this truck. I really liked that Highlander with a 400SBC/4spd. It drove like a truck with plenty of bottom end torque. I guess I could just put the 4spd/NP205 combo I had for that '71 shortbed. I know I'm fickle,but hopefully the day will come when I can do another 4wd and satisfy my need for variety.

[OLDCHEV4X4]

Originally Posted by special-K

Randy,I guess this truck's the same set-up as yours,except for TBI 454

Well if ya need any pics or anything, let me know.

There are slip yoke eliminator kits out there, I dont remember where I saw it though. Mabey AA.

[obijuan]

Take the rear housing off your 205 and remove an replace with the slip yoke. Whole housing will come off. No need to pull it all apart.

This a post 85 400/205? If so it uses a different crossmember and mount. Snag that.
the kickdown is not really even necessary. Ive driven mine without it for a few years.

You can swap front output shafts in the 205 and use yoir cv yoke and not the flange.

That 4l80 241 shaft will be close but probably too long.

[special-K]

I'm buying the late TH400/NP205 soon. I'll get the crossmember. I kinda figured but wasn't sure if I "had to" have it. It's a TBI 454 truck,so I'll use stuff from an earlier TH400 set-up. I've gotten by w/o that but want to do this truck to be "as factory" as possible. Basically,it'll be a phantom '72 GMC Sierra K3500

[BurnoutNova]

I was going to swap in my th400/np205 in my 71 K10, and like you have decided to save the th400 setup for another truck. I was planning on moving the motor forward and leaving the trans where it was so I didn't need to change the front drive shaft length. At least that was my plan, who knows what else I would have ran into.

[special-K]

Yeah,I'm going round and round on this. I definitely will grab this unit for something,though. I just "gave" the 4L80e/NP241,ECM,harness,and speedometer out of my old '91 Suburban to a good friend that has done some big favors for me. He's got an '85 K3500 that he tows a lot with. He's about to change engines and it just seemed right. But,then again,he has a 4spd '89 Blazer he's parting. Hmmm...Lo NP241 gearing,hydraulic clutch,I can use my stick speedometer in the '72...