Has anyone had any experience installing a new transmission mount ( or reinstalling the old one ) ?
I just put the engine back in the car…and find that I need to compress the spring in order to fit the plate to the underside of the trans.
Spring is stiff. Do you just use a jack and push the plate and spring assemble up, hoping to align the plate bolt holes along the way ?
Should I remove the engine mounts…raise the engine…and put the spring/plate assembly on, allowing the “pin” on the rear of the trans to drop through the hole ?
Any advice/help is appreciated. I’m at full stop on the engine now because of this…
Thanks,
There is a cross hole in the pin. It’s probably easiest to install the mount and then use a large cotter pin to hold it all together. Then mount it on the car and remove the cotter pin. Or use a jack to push it in place and some long pin punches to help align the holes before installing the bolts. It might be good to check the threads in the captive nuts as some of mine were stripped and needed to be helicoiled.
And don’t succumb to the temptation to draw the plate up by screwing the bolts in. Rather, reduce the stress on the threads by using the jack to compress the spring then screw the bolts.
Why will that make any difference? Once installed those threads are under maximum stress 100% of the time. Winding it in from an uncompressed spring position must be less of a stress than that.
I’d simply wind it in with long bolts and replace the bolts one by one with shorter bolts and then the final bolts as the length allows.
I was advised against using the bolts to draw it by a well known, currently banned, contributor here after I had already caused some thread damage to one bolt/nut by doing so. I think the operative theory might be that a given size/pitch/material thread is suitable to establish and hold a final torque spec but not to work against any substantial torque for any substantial duration. As I recall, those are 5/6 fine?
I would think using the threads on the bolt to draw the mount into position against the spring pressure being exerted against the threads would place stresses on the threads that are different from when the bolt is stationary and simply exerting a clamping force.
Then consider the fact that if the bolts are used to draw the mount into position the bolts are being turned one at a time, so most of the force of the spring tension is being put on that one bolt that is currently being turned. Contract that to when all the bolts are in position and the force from the spring is distributed more or less evenly over all the bolts.
Agreed. I would hazard a guess that the reason that the threads are sometimes found to be stripped on those captive nuts (as @WWayman reported his were, as were some on my car) is that they were used to draw the mount into position under load, with the “grinding paste” of oily grime common in that location only helping the thread erosion process.
That is why I used lengths of all-thread, slotted on one end to accept a screw-driver blade. That way the nuts on the all-thread take the stress/wear, not the captives.
I was lucky enough to have a set already made up as they are used for R&R of TR gearboxes.
The grinding paste argument only works if you do NOT spread the load, as three or four out of five are done up unloaded.
I would have thought that the load ought to be spread more or less evenly if no bolt is done up more than half a turn at a time.
If you start with long bolts, to make sure they cannot slip out, then there is no downside in using a jack. All I have suggested is that the loading isn’t fully taken up if the spring is not being fully compressed, so it is a lot less stressful than people think, especially at the start, when dummy long bolts are used to start you off.
I’ve used long bolts to orient the mount to the captive nuts and then used a large socket on top of a bottle jack to push the mount into position. Trade the long bolts for shorter ones and the job is done.
Rather than using bolts to wind up the last 3 inches of the front road springs on my XJ6 I used 9/16 studs cut from continuous thread. The welded together double length nuts took the frictional load keeping the threads in the spring cup in the normal “unworn” condition. I swapped out the studs for permanent short bolts when all was closed up. Perhaps this way might work for the POs cross member. Paul.
Thanks to all for their suggestions. Here’s what we chose to do:
assembled the pieces of the spring mount to insure proper fit.
put a small block of wood on the roller jack and positioned it under the transmission mount location.
while one of us held the spring mount / plate in position, the other cranked the jack up to meet it…and we positioned the wood block so that it did not interfere with the bolt/pan holes.
we kept raising the jack so that the spring was compressing…allowing us to get the pan close to the underside of the body.
once there was a “friction fit” with the wood block and pan, we placed an awl through one hole in the pan and lined it up with it’s mate on the underside of the car. Once done, we removed the awl and loosely fastened that one bolt.
we repeated the previous step for the remaining holes / bolts.
we left the jack / wood block in place while we tightened down the bolts.
lowered and removed floor jack…and double-checked the bolts for uniform tightness.