The Stovebolt Site Forums The Shop Area Engine Shop Tranny mount swap

I have pulled the 283 and 4 speed tranny from my 59 3800 1-ton, and i want to replace the 283 with a mid 70's 350 and 350 turbo tranny, is the old 4 speed shorter than the automatic 350? is it possible to reuse the oem 4 speed tranny mount where it is in the frame? the tranny that i want to use is in my daily driver so i can't mount it in the frame untill i'm ready to use it. Has anyone removed the oem mount and slid it down the frame and altered it to work on an auto tranny?? I don't have the $$ to buy an aftermarket 350 tranny mount for my truck right now

The original 4 speed does not have a support. The bellhousing bolts to a crossmember, the engine, and the transmission. The transmission is cantilevered off the bellhousing. If you are replacing to an automatic transmission, you will have to fabricate a new mount for the transmission, as you will be losing that bellhousing mount. The TH350 is quite a bit longer than a 4 speed. A new driveshaft will also be needed.

The frame crossmember that holds the tranny is what i'm talking about, it should be possible to cut the frame rivits and move the crossmember down the frame rail to another spot and reuse it for the auto tranny mount, then cut the front half of the 2piece drive shaft down before the cairrer bearing and mount the auto tranny yoke right to it, that should work don't you think?? Or do i need to ditch the carrier bearing all together and just get a 1piece driveshaft that will fit?

I see a problem with what you are trying to do. The 59 V-8 front mounts are on the very front of the engine so if you only use a rear mount on the rear of the trans the engine and trans are not supported correctly. My suggestion would be to purchase an aftermarket front crossmember (and mounts) which moves the mount location to the center of the engine. Also purchase a rear crossmember to mount the rear of the trans. These parts are availably through a variety of aftermarket suppliers.
You can use your existing drive shaft by having the front section shortened and add the correct yoke. This should be done by a professional driveshaft shop which can also rebalance the assembly. You may have to cut the rivets and remove the existing crossmember to clear the new auto trans but I would not attempt to use it in another location. As mentioned previously the trans does not mount to the crossmember, it bolts directly to the bellhousing and the belhousing is bolted to the crossmember in the stock application.
Fred

If it was me ,I would use the four speed and just change the engine.Just make sure you put the pilot bearing in the crankshaft.

If i did mount the motor with an aftermarket tranny mount and the oem front mounts what would happen? would it cause too much stress on the engine/tranny connection? how did chevy mount the 283's with auto trannys back in the fiftys? If i go with an aftermarket crossmember motormount where on the frame do you mount it? do you just use the front motormounts location as a guide and slide the new mount down the rail till it's where it needs to be?? I've never done this before so bear with me

I have fixed a couple of TF trucks that had the mounts installed as you mentioned. It will work for a while but the engine and trans will eventually flop around until something breaks.
The original automatic trucks in that era used a similar rear crossmember which bolted to the sides of the hydromatic bellhousing. If I remember right the mount kits came with instructions which had dimensions and locations. You have some flexibility about where to install the mounts when making a later model engine/trans conversion.
Fred

Like one fellow said you can get a side engine mount conversion for the 350 cu. Chevy V8 but depending on the trans mount which mounts on the tailshaft of the transmission. I made mine out of some 3"x1/2" flat and two pices of 1"x 1/4" flat welded on edge to keep from flexing. I bought a trans rubber mount and fit it to the cross member I made. On my 62 the frame makes a X in the center and I bolted the crossmember to that and to the outside frame rails with 3/8" Grade 8 bolts,washers,lock washers and nuts all being Lock Tighted and torqued to specs.. One thing to remember Chevy engines are set up to be 3 degrees back drop to the rear of the chassie. at the carb. off level.
62Blue
Don

well i removed the crossmember that mounts to the bellhousing and tranny today, man bangin out 50 year old rivits aint easy, now that it's out, do i need to remove the front motor mount mounts that are on the front crossmember? if i leave them will they be in the way of anything? it seems to me that if i use an aftermarket v8 motor mount it will interfear with where the brake lines go thru the frame and meet the rubber lines to the front brakes. there is an 8 inch difference between the center of the front motor mounts and the center of the side motor mounts on a 283/350 engine, i was thinking if i just measured from center of the frame mounts on the front crossmember back 8 inches that would put me on center of the new motor mount, the engine would be in the same spot that it was in before i removed it, just mounted more securly. has anyone done that and made it work?