Not sure if this should go here or in the 73-79 forum, but I'll cast a line here, as well.

I'm about to pull my 300 out of a 1978 F250, separating it from a T18 tranny at the bellhousing. I don't have a transmission jack, so is it safe to rest everything on the crossmembers for a long time?

 

Are you meaning just leaving the transmission "as is" bolted up to the crossmember? If so, then yes. The crossmember generally supports the weight of the transmission anyway.

 

It's not the best for the transmission mount or the tailshaft housing. I like to run a chain around the frame rail from side to side under the front of the transmission. It helps support the weight and takes some of the stress off the mount and tailshaft housing.

 

Why would it make any difference? The transmission is only 80 - 120 lbs depending. How's it going to hurt the transmission mount. Or the tailshaft housing when it's resting on the mount?

 

Is the truck a 2wd or 4x4?

If it's a 2wd then it has 2 crossmembers. It will have the one under the bellhousing which is basically a support at the strut rod brackets. If it's a 2wd just wedge a piece of wood or something between the bell housing/transmission and the crossmember to keep the transmission sitting at close to it's original height.

If it's a 4x4 it depends on if he is talking about unbolting the mount from the crossmember and sliding the transmission back to set it on the crossmember( wouldn't work so good with the transfercase ). Or leaving the mount bolted to the crossmember and just letting the transmission hang.

If it's leaving it bolted in place. The problem is most of that transmissions weight is in front of the mount/crossmember. Take a 100 pound dumbbell in your hand. Lift it straight out in front of you with your extended arm. It puts a whole lot of strain on your elbow & shoulder ( especially the longer you hold it out there ) . The T18 is a short transmission but the mass of it's weight is still in front of the mount/crossmember. The 4x4 isn't quite as bad because the NP203 or 205 will help counter balance it some and I know the 205 has a second support mount on the driverside. I don't remember on the 203.

That being said I've bought trucks that have had the engines pulled with transmissions left in place. But I've also bought transmissions that had cracked/broken tailshaft housings.

If leaving it bolted in place. It's not that difficult to support the transmission with something. It could be a chain, a jack with some kind of block( if needed ) , a stack of wood blocks or cinder blocks, whatever. It's cheap insurance over doing nothing and possibly having a problem. 9 out of 10 times it would probably be fine. I just know with my luck I'd get the 1 time it would cause a problem.

 

That definitely makes sense. I think too often I forget that all I've worked on is 4x4 and that 2x4 is a different story in some respects. Either way, I've never let it sit for much longer than a day or two while doing an engine swap, so never really thought about what the longer term ramifications would be.

But you're totally right, there's no point in NOT taking some cheap insurance to be sure it's okay.

 

I am with fordman, support the trany.
Sometimes wile pulling the motor a floor jack will work to support it till the motor is out in case you have to raise/lower it to get them apart.


Long term I like to use a ratchet strap around the frame.
This is what I did to my parts truck to get it home on the trailer so it would not hurt the trany or mount with all the weight on the front of the trany.

BTW don't do it this way as you may hurt the cowl!
Dave ----