theoldsarge

Background: My son recently bought a '91 Dodge truck, with a 5.9 Diesel, that is on about its 4th trans. He also recently bouth a '91 4X4 Suburban, with a TH400 trans, and a blown 6.2 Diesel V8 engine. He wants to put mate the Cummins to the TH400, and put them in the Suburban.

I've been spending a LOT of time the last few days surfing the web, and here, along with making some phone calls on what exactly will be needed to do this swap, and where to get the parts. So far, about the only thing useful I've come up with is the number of a guy in Washington State that will sell a kit for the swap, for $1600. Comes with adapter, flexplate, centering hub, all bolts, and a starter. My son thinks that's too high and he can put in a NV4500 for considerably less. But, he would prefer the TH400.

I've read a lot about this swap having been done, but a lot of conflicting opinions on it. Some people say you need an adapter, but neglect to say where one can be gotten. Others, claim it's a bolt up, which I rather doubt.

Can anyone here tell me what parts he will need to do this swap? About what they will cost? And, where he can get them?

I would appreciate info on anything I may have forgotten, or if additional info is needed. It's like pulling teeth to get anything out of him, even tho this is at his request. Kids.

Thanks
Theo

59FORD

Well "DAD" it depends on who is doing the paying.

If he is on the 4th trans I would suggest he get a job and learn where $$$ comes from.

The $1600 I feel is a bit too much. You can dig around the boneyards and look
for old bread trucks, Frito Lay trucks and a few others.

There are a lot of these trucks that had the 4BT Cummins with Ford C6 and GM 400's
behind them.

The adapters will fit the 6BT Cummins also.

The NV would be the strongest trans for the money, again "depending" on who's paying.



IMHO

spunbearing

I was looking into doing that myself because I was thinking about getting rid of the getrag and I happened to have a TH400 sitting around. Heres the problem. Even most of the race built TH400's are rated at about 400 ft. lbs. of torque. The stock cummins will shred a TH400.I have mild bombs on my truck and suspect that I'm in the 550 ft lb range. If he has a bone stock cummins and a light foot he may get away with it for awhile but I'm not gonna try it.

theoldsarge

No, I'm not paying, just gathering info, he doesn't have the time to do that, he works, and long hours at that. He bought both truck with the parts already broken, he didn't abuse either.

We don't have any junkyards around with Frito trucks, and fewer you are allowed to poke around in. Besides, he dosen't know what all he will need, or what fits what. I'm trying to help him by finding out.

I have figured out, finally, the adapter from the 4Bt would work, but haven't been able to find out what else will, or where to get an adapter, plus whatever else is needed.

And, yeah, he already knows the NV4500 would be stronger. But, also more of a PITA to install. The Suburban already has a TH400 in it, which is one reaason why he wants to go with it.

I don't think he'll have any major problems with the TH400. First, he's not going to be hammering it; and, second, there's been a lot of these swaps done already, with TH400s, with no problems. The only concern has been digging out the info needed.

Theo

Mcmopar

Save yourself a big headache, get a 618 from a 1994-1995 CTD and put that unit in place of the 518 that it has.

theoldsarge

I'm not even sure what a 618, or a 518, are. Different transmissions, I take it. And, it's not my headache, it's my son doing this.

Regardless, you seem to be missing the point; he already bought both vehicles, around $1,000 total, and needs to keep costs down. He's got the TH400, he wants to go with that.

Theo

spunbearing

I give it six months... good luck

RandyW

Theo,

Try this guy - Jaime Avant at Diesel Depot
P.O. Box 228
Sandersville, Ga. 31082
800 553-8192
avasalv@mylink.net

Also, keep an eye on E-bay. You're wise to shop around. The parts you want are readily available but keep digging for the good prices. Good luck.

Randy

Mcmopar

The 518 is probably the tranny in the CTD, the 618 is the newer and more heavy duty version, if you can get the 618 it bolts right in, and will be a lot less money. If you are trying to keep costs down a 1600 conversion seems totally out of the question. If you get a 1996 or newer 618 or 47Rh/e you have tons of electronics to deal with. The 47RH only has electronics for the lock-up and the overdrive, three wires.

theoldsarge

I have already been referred to Diesel Depot, but not been able to make contact yet.

Anyway, have finally come up with what seems to be an accurate list of what my son needs to make the swap, just not sure where he will get them, yet. Apparently, these are still listed by Cummins, so one otion would be purchase new.

Item list:
- Trans adapter, w/starter flange.
- Flexplate adapter, 146 tooth, 10-12 pitch ring gear.
- Eight hex head screws.
- Crank adapter.
- Torque converter adapter.
- Six cap screws.
- Flexplate.
- Clamping ring.
Not sure yet, if another starter will be needed, or not.

Also not sure if this is the exact terminology, but it's a start.

I think I've gotten all I need here.

Thanks

Theo

apache

What about gearing? the sub probably has 3.73s or 4.10?Im not sure what the diesel chebys came with. without an overdrive he gonna be spinnin on rpm at 55 if that. Just something to consider. Unless he`s gonna run 35`s or 38`s or?

6 2 Carl

1991 was the first year GM started using the 4L80E overdrive transmission. So if the suburban has a TH400, it must have been swapped in or, the suburban is a 1990 or older.

Carl

spunbearing

Am I the only one that thinks that 400 ft. lbs. of torque will shred a stock TH400 to pieces? I know it's a hearty trans but when I was considering the swap I couldn't find a builder anyplace that would rate a TH400 for 400+ ft. lbs. I think it's asking for trouble. I hope that I'm wrong.

theoldsarge

No idea what gears the Suburban has, that's his problem. But, I'm sure he's gonna lift it, and put the biggest tires on it he can.

According to my info, overdrive was an option in '91. To me, that says they still used the TH400.

The TH400 was factory rated at 451 ftlbs of torque. Don't know where you live, but I live outside a small town, and no problem about finding a trans shop to rebuild one to take more than that. I just read an article about a turbocharged 455 Pontiac, over 600 ftlbs of torque, street driven, drag raced, and lives.

Theo

Nevada

The gasser Pontiac would be making that kind of torque near it's RPM limits. The CTD would be hitting high torque numbers a lot closer to RPM numbers that a grocery getter would see. A CTD hits the top of it's torque curve every time you drive it, that turbo Pontiac would probably only see those numbers infrequently unless it was on the track.

I am no tranny expert, but this sounds like one of those things that you can do but shouldn't.