The GMC CCKW

CCKWX and CCKW trucks before Chassis No. 41224 had exhaust systems that exited on the Passenger Side and not at the Left Front Mudflap.
This was because of the early Vacuum Assist Brake System. The location of the Power Cylinder and it's linkage behind it required the location of the muffler and the tailpipe in a manner that it exhausted to the right.
There was a special exhaust pipe that crossed behind the Transmission Area, the Muffler hung in the area that the later hydrovacs would be and a tailpipe with interesting bends was placed behind it. There were two SWB Tail Pipes, GM 2147244 for the SWB Banjo, and GM 2140864 for the SWB Split Axle 6X6. The two Tail Pipes were not interchangeable between models.
Bob Rubino @ Mil Spec is restoring an early Banjo CCKW SWB at his facility in NJ. It has the early brake and exhaust system, he has been lucky to obtain the correct NOS Exhaust components.


My SWB had the original early system, but has been upgraded to the 1st Series Hydrovac system. All holes for the later system with it's new brackets have been installed precisely in the correct places. All that remains of the mechanical system are the bushings and their brackets in the Chassis rails.
Joel

My truck had only the exaust pipe coming from the manifold and ending just under the driver side of the cab. I have rebuilt the exaust in accordance to the 1944 TM I have and it does quite well for the old beauty.

Not many of todays CCKWs will be found with original style muffler clamps, the U-Bolt type are not Factory style. It is best to use the original style if you intend to reuse your exhaust pipe or tailpipe after muffler replacement. NOS Exhaust pipes in the US are just about extinct. The use of a tailpipe will enhance to the original sound of a CCKW.

The exhaust manifold was different back then too.

The CCKWX till ?? had the exhaust pipe bolt flange with one bolt directly behind the manifold. It was a bit tough to put this bolt in. At some point, they changed the manifold by rotating the flange so that there was a bolt hole away from the engine and towards the fender. It was mauch easier to put the pipe on.

I think you have it mixed up, looking at all of the engine views in the WWII TM10 parts manuals and SNLs, it shows the single stud facing the fender. There were two part numbers for the WWII 270 exhaust manifold,and I have both on my shelf, what happened , beginning in the 50s with the M-Series GMC is that the 3 bolt pattern on the exhaust manifold(same casting number) was changed and there was one bolt of the three, that was directly toward the Block. The M-Series 302 used the same Casting Number as the CCKW, but the flange was turned 180 degrees. The late exhaust manifold was available thru GM into the 90s when it was discontinued. My guess is that when the Gov't needed CCKW exhaust manifolds in the 50s they received the same ones that were cast for the M-Series. The NOS exhaust manifolds are a rare commodity today.

Actually I think I have it right. I had a CCKWX at one point and as I recall it had the hard to get at bolt. The new mil 302 manifolds I have been buying I believe also have the hard to get at bolt

My ACKWX manual shows the exhaust system just like normal trucks and they had the mechanical booster too.

Was the funny exhaust only for the 352?

There may be casting date codes on the manifolds, but the M-Series manifolds have been produced since late 1950, early 1951, and they have been in the Army system since 1951. There is a good chance that they were used to replace CCKW starting back then. The 270 manifold as we know it has been around since 1939. The Army used it on the DUKW, CCW, CCKWX, and CCKW.

Joel,

Do you have any picture showing the SWB (split) tail pipe your are describing? ( GM 2140864)
I´m working on a CCKW 352 with early brake booster and serial number is 37349 B1.

Thanks,
Ducatti