TH400/NV4500 conversion + Tow Rig Build Thread (PICS)

[Wrench]

Subject is my '82 crew cab K3500 dually. Currently it has the 6.2 diesel/TH400/NP205.

I'm swapping in a 6.5 TD/NV4500 and need to mount the NP205 behind it. My np205 is the old racetrack pattern though, and I understand that most people just buy a later model NP205 with the round bolt pattern. However, I've heard that the weight of the NP205 can be a problem on the NV4500 because it has an aluminum tailhousing and the NP205 is a lot heavier than the NP241.

What I'm thinking is that I'll machine an adapter that I can cut both patterns into, the 8-bolt pattern countersunk on one side and the 6-bolt round drilled and tapped. That way I can bolt the adapter to the NP205, then bolt the NV4500 to the adapter the same way it normally bolts to the NP241. Finally, the lower half of the racetrack pattern, which will be exposed below the tranny, will allow me to bolt a crossmember up so that the t-case isn't hanging on the NV tailhousing.

I already have: the early model 4wd NV4500/mechanical injection 6.5TD out of a 93; an 85 2wd one ton Chev that will donate a factory hydro clutch pedal setup that bolts right into my cab; master/slave cylinders from both the 93 and the 85 so I can use whatever works best; and my NP205 from behind the TH400 with the 32 spline short input.

The 32 short sticks out 1-1/4 inches from the t-case, and the NV tail sticks out around 1/8 inch beyond the mounting surface on the tranny. So that leaves me with 7/8" engagement if I use 1/2" plate for the adapter-yes?

I'm thinking of putting in the 32 long instead, which sticks out 3-1/2". However, it's only bored 2" deep (thanks 4x4HIGH for measuring for me).

The tailshaft on the NV4500 is splined at least 3" back from the front. As I see it right now, I can use 3/4 inch plate for the adapter, which will give me lots of room to countersink bolts and lots of thread for the tranny bolts. Then I can slide everything together, measure how much room is left, and cut the NV4500 tailshaft back just enough so everything bolts up tight.

Am I missing something?

 

[4X4HIGH]

You ask for the measurement of the length os the splines. The splines are 2" long but the bore is a bit deeper than that. I can measure that for you tomorrow.

 

[Wrench]

I never even made the distinction in my head, thanks for pointing that out.

My machining experience is non-existent when it comes to inside splines, if the bore is deeper would the shaft be able to extend past the end of the splines, or is the bore is the same ID as the ridge on the splines?

 

[4X4HIGH]

The shaft could go slightly further than the end of the splines in the input shaft. I'll get you that info tomorrow once i'm back at work. IIRC though the short input is the same way so you could measure how much further it could go there and then add the 2" of spline.

 

[4X4HIGH]

I just measured how far an out put shaft could go into the long 32 spline input and i come up with 2.625" (2 5/8").

 

[Wrench]

That should be perfect then, I'll just use a 1" plate for the adapter. Should still leave a hair open at the back of the hole with LOTS of spline engagement

I'll go ahead with that swap we discussed then, shoulda asked all these questions first . Let me know about shipping, I'm off to the wrecking yard for goodies . . .

I'll put pictures up when I get the adapter cut and drilled.

 

[bp71k5]

You might consider moving your rear crossmember to support the back end under your adaptor instead of letting the 205 hang off the back of the rear output on the tranny. You could tap some mounting holes into the adaptor to match the crossmember. I did a similar conversion and added a doubler at the same time. The doubler adaptor has mounting holes like this.

 

[Wrench]

I was actually thinking of putting in a second crossmember, so one under the tranny as normal and one under the adapter. That might be overkill though . . .

 

[Wrench]

major junkyard score on Sat.

Picked up a complete '83 crewcab cab fully loaded at the wrecker on Sat. with absolutely spotless rustfree floors. Was a 2wd, but has the 4spd so it still has the bolt down tranny hump. Has a/c and cruise like mine, + the bedlight/cab brake light top center on the back of the cab. Been looking for a solid cab because mine completely rotted out under the carpet as you can see . . . .

And the passenger side is worse . . . Anyway, yanked the entire cab, complete with colum, AC stuff, entire interior including seats, but no doors, and paid $110 . Rockers and cab corners need doing, but otherwise no rust anywhere. My planned "truck reno" is getting bigger all the time . . .

 

[Ten_Bucks]

This looks like its gonna be a good build. *Subscribing to thread.*

Scott

 

[Wrench]

Today I ordered an Energy Suspension polyurethane cab mount kit and leaf spring bushing kit off Ebay--$142 including shipping for both kits Just wishin' I could drop everything else and go start wrenching

 

[Russell]

Too bad you didn't post up about needing a crewcab last year around this time, I had a totally mint condition cab you could have picked up free

Do you need any sheet metal for it? I've got a fairly nice 88 front clip for it (single headlights, looks like the 84-87 trucks)

 

[Wrench]

No kidding, what did you end up doing with it? Now I'm peeved I didn't find this truck earlier

Today I snapped up another sweet deal--a late 90's Cummins intercooler, like new condition for $140. I'll be installing it with my 6.5, then when I go Cummins it'll be all ready

Fits 92-2000 models, and for those who are thinking about or planning to install one . . . finned area is 16" h x 36" w, width between the tubes is 40-3/4, and overall width is 46". Thickness is 2-1/4, and it uses 4" OD tube.

How's that for a sweet deal? It came with what looks like an a/c condenser on the front, but I'll be running it right out in front of everything, only the grill in front of it, so I should get more effective cooling than the Dodges do!!

 

[Russell]

Looks nice man! Lemme know how it fits, maybe I'll put one into my 80 and run a few more pounds of boost

 

[Wrench]

Well, I'm finally getting into it. Last week has been a busy one This thread is officially being converted to a tow rig build thread.

I started by tearing into my 6.5 and found that the block was cracked, so I may just do the turbo conversion on the 6.2 or I'll have to find a 6.5 short block. Trying to keep the money flow to a minimum

I've found that laying out the tools ahead of time saves alot of time.

Yesterday I pulled apart the front clip on my dually and started breaking it down, so this morning I brought in the rad support/core and started chopping it to fit the intercooler in. The cooler intake/outlet pipes are about half an inch too narrow to fit the stock 6.2 rad between, and just a hair narrow for the 6.5 rad. I'm going to call some shops tomorrow, see what I can do about that. With some chopping and welding on the support, I think I have everything fitting in nicely apart from the rad problem.

As you can see, the A/C condenser moves out front, with a modified front bracket so there's room behind it, and with some significant chopping, the intercooler fits where the condenser used to go, centred on the rad so that the rad can go in its stock mounts. I'll do some more playing around with the pieces, so that all things finned ride on rubber, and weld up some bracing to take the place of what I cut out and keep everything nice and stiff.

After lunch I went out and pulled all the wiring, inside and out, from my truck. The PO had wired and rewired a number of different trailer plugs, lights, and various other switches and miscellany and completely screwed up the electrical system. I could turn the truck off and it would keep running if the lights were on. The glow plug light faded in and out the entire time the truck was running. Interior lights came on and off at various times, and the wipers had a variety of interesting habits. So I brought all the wires inside and will inspect/rework the system.

I discovered that the only difference for the inside cab harness between gas and diesel is the harness for the glowplug light/timing control and the water in fuel sensor. It's a standalone harness, and fairly simple.

This is my truck as it now sits

Wondering if it's possible/easy/difficult (read expensive) for a rad shop to narrow an existing rad by half an inch? My experience with rad work is zilch. Any opinions from somebody who knows?

 

[Wrench]

Not a lot exciting happening today, I stripped my 205 down, ground the rail for twin sticking, and started cleaning the case and parts. Also finished patching the wiring harness, soldering each joint and covering it with heavy duty heat shrink.

--I'm planning to use 7-wire trailer cable to run the taillights and trailer plug, so I just have one heavy duty cable running from the front to back of the truck for both truck lights and trailer plugs.

--I'll also likely put an RV plug in the box while I'm at it, run two heavy power supply wires into the cab that will be dedicated to CB, stereo, and amp, with 30A inline fuses on both. I can't stand wires patched into each other all over the place, and overdrawing the existing wires is just asking for trouble.

--Went by a rad shop yesterday, guy really knows his stuff. We got to talking and he said just for fun he once welded two pop cans together. Anyway, it would cost $650 to recore my 6.2 rad one inch narrower but with a 4-tube high density core. I'll do that later this summer, but for now I'm using the 6.5 rad, which fits width wise but is two inches shorter top to bottom.

 

[Wrench]

Starting work on my new cab, trucked it into my garage last night and I'm going like gangbusters. Floors are pretty good, but I'm sanding the front pans down to bare metal and figuring out something better. I've installed some commercial roofs, and I'm thinking of putting torch-on (S.B.S. modified bitumen membrane) on the floor. It's a heat-weld application, so basically it melts right to the metal. It would also help with noise and vibration.

Here's my brother sanding away.

The driver's side pan untouched--it's really cool to see Chevy sheetmetal that's just on the verge of going bad cause you can see where the rust starts very clearly.

Other big job is just because I'm a dumb noobie--when i picked the cab up at the wreckers I used a single strap through the door openings and this is what happened--it was still completely trimmed out at that point.

So I skinned the inside ceiling of the cab, which comes off in a convenient section after drilling out the spot welds and gives easy access for pounding out those dents. While i'm in there, I'll zinc prime everything, and dump some POR-15 into the joint at the top of the door pillar to stop further rust.

Keep tuned--and give me some FEEDBACK already!! I know it's not a sweet rock crawler build, but still . . . .

 

[Wrench]

Also finished putting my NP205 back together with the long input, new seals and gaskets all around, and modified shift rails for twin stick. They seem to work too

 

[Russell]

Lookin really good!

Wish that the regular cab roof was so easy to remove!

 

[Wrench]

Lotsa updates now . ..

Went to Princess Auto and bought a 10 gallon pressure feed sandblaster, shop crane, and HVLP spray gun for $400. Makes the job more fun anyway . . .

Finished cutting, and am sandblasting all the cab supports/framework underneath to prep for POR-15. Also sandblasting the firewall in prep for applying torch-on as a sound deadener. Anyone ever used it before--I'm a roofer and have a few rolls sitting around, it heat-welds to just about anything and is basically a 1/8" thick sheet of rubber.

Got my tranny to t-case adapter from the machine shop and finished it by cutting the notch for the shift rail and threading the holes for the tranny bolts. I had the center hole machined to fit one of the extra seals that came with my kit from Northwest Fabworks, so the t-case and tranny fluids will be kept separate.

Also got the old cab off and the auto tranny pulled, leaving just the engine on the front end. After checking the casting numbers on the engine I discovered that I have an early 96 6.5 block under the 6.2 induction system, which is kinda cool :-) I now have 3 complete 6.5 blocks, though one is shot. Dang.

The other really awesome thing is that with the custom adapter, the tranny/t-case combo are less than 1/4 inch different from my old combo, meaning I don't have to change my driveshafts. That alone pays for the custom adapter, and I get the added benefit with the long 205 input of having over 2" of spline engagement between the t-case and tranny. Should be able to handle any torque I can pour through it . . . The three bottom bolt holes on the NP205 will be used to attach a custom mount, keeping the weight of the t-case/adapter off the NV's aluminum tailhousing and also helping to prevent excessive drivetrain flex.

Well, I'm back to work, hoping to take this ol' girl on her maiden voyage March 15th when I drive out to BC for a late-season snowboarding trip