Can a cracked transmission be welded?

Question

I have a 1991 GMC Sierra 4X4 extended cab 5.7l. the transmission is leaking and when I took a look it appears to be coming from a crack in the passenger side.

Can it be welded? would a weld hold? or is there somewhere I can buy just the caseing and transfer my gears and everything into it?

Answer 1

If the tyranny is cast steel or pot metal it is possible and so is aluminum, however there is a lot of prep to do and if the crack is on a pressurized area you could be asking for trouble. It it is a crack in either case you must warm up the metal to find the ends of the cracks then you must drill out each end of the crack. then you need to get the oil contamination out of the crack so if oil comes out of it with it sitting you have to remove enough oil to stop the leak to prepare the leak then you will have weld it. if you use a mig it will be a pain and dangerous, a gas torch will do it but you will have to buy a special coated rod to weld aluminum with gas if it's cast you will have to buy a special rod and do it with a gas welder but better with a stick welder. You could try trying JB Weld on it clean it as before and lightly sand it. If it's aluminum get JB weld for Aluminum get the fast set if it's pot metal get the regular stuff if it works great it's less dangerous and cheaper. if the JB weld does not work you can buy titiaum putty mix it and prep it as before

Answer 2

I think it would be tough to weld. It's probably aluminum. You can do it, but I think it's pretty thick and would be tough to do properly. Also, that crack has probably changed the centerline of the transmission. The hole in the front of the case is probably slightly out of line with the rear hole now. So you might have trouble keeping bearings and things from failing due to side loads and stresses. If the crack is actually just a porous weakness, I guess you could weld it, or even try something as simple as JB Weld or something like that. You can get the quick dry JB Weld and try that without spending much time or money. It's already cracked anyway, might as well go for it.

Answer 3

No it can't.  The casing is a structural component, and the crack will migrate under the stesses of normal use.  On a transmission that old, I would recommend you replace it with a Jasper unit.  Jasper takes the unit from your truck, rebuilds it, and then re-sells it.  Just as the unit the they would sell you.  They are as good as or better than OE equipment.  This is what I used in my truck.

Answer 4

i had a 78 pont. bonneville once and it had a crack in the transmission case and i cleaned it out good with carb. cleaner and used jb weld. i had that car for 11 yrs. after that and no more leak.

Answer 5

It wouldn't be a good idea. If the crack was even a few thousandths of an inch wide You might stop it from leaking and spreading with welding, but you could still be putting some serious stresses where you wouldn't want them. The heat from the welding could do damage too unless you disassembled the tranny first. You'd do a lot better just to get a factory rebuilt.

Neither Jasper or anyone else will want the old one for a core if they know it's cracked.