I am finally changing out the front upper sub-frame mounts. I have the engine supported and am starting to disconnect the shocks, brakes and steering linkage. Any tips or advise on doing the whole project would be appreciated

Thanks in advance,
Ed

 

i JUST got that done... paid someone $300 though...

 

Was the rubber torn from the metal on yours? I just got mine off of the subframe and the rubber is still bonded to the metal

 

Yeah, the rubber and metal were totally separated....

 

This is located where? I need to go check mine out. I also need to replace my upper shock bushing for the front shocks.

 

Symptoms include a hard braking with the engine shifting up, a feeling of the brakes releasing prior to stop... Or hoist the car and pull on the engine from below and it will move.

 

Nice one, I think I have these symptoms....may as well change v mounts when I drop my subframe I think....

 

Any demon tips?

 

I finished changing my upper sub-frame mounts and found some short-cuts that really make the job easier if you are only changing the upper ones. My rear bushings do not have any excess play so I left them alone which made the job far easier. The short-cuts I used will not work if you are changing out the tops and the rears.

First I supported the engine using a 4x4 post with some 1" wood pieces that fit into the inner fender lip. I used tie-down straps from the engine around the post and some wedges to get the straps tight. Worked fine with no damage to the fender lips

Next I supported the car on jack stands high enough so that I could work under the car on a creeper. I removed the front wheels, the upper shock bolts, the motor mount bolts at the subframe and loosened the rear sub-frame bolts. I unbolted the steering rack from the subframe but did not disconnect the the steering shaft or the hydraulic lines. I had to do this because the steering shaft and U joints are badly rusted and they were not coming off. I don't know how I would have gotten them apart with damaging the steering gear or the rack. I just let the rack hang from the steering gear and this worked great and saves all the work of draining the system and disconnecting the hydraulic lines.

As I was only planning to lower the sub-frame enough to get the top mounts out I left everything else connected to 1st see if I would have enough play to do this. This saves a huge amount of work as the brake calipers, tie rod ends and all other components don't have to be removed. I did disconnect the ABS sensor cables from the body to give me room to get to the rear bolts that hold the mount to the sub-frame.

Next I supported the front of the sub-frame with a jack and removed the 4 bolts that hold the sub-frame to the body. I slowly let the jack down and the sub-frame pivoted down (on the bolts of the rear bushings) enough to get a small ratchet and tork socket between the engine and the sub-frame and remove the bolts. Fortunately the 4 screws holding each mount were not rusted nor over-torqued in place (this is a 1st for any fastener underneath my Jag). The sub-frame drops down and rack stays in place without putting stress on the rack or hydraulic lines.

With the old mounts off I treated and painted some surface rust where the mounts sit on the sub-frame and bolted the new ones in place. Here is the tricky part. The sub-frame would not pivot back up into place as it had moved forward about 1/2' and the studs at the top off the mounts won't go into the holes in the body frame. To pull the sub-frame backwards the 1/2" I took a treaded rod with the hooks from a spring compressor and attached one end under the subframe (just in front of the where the rack mounts) and the other end to the eyelet on the bracket where the rear of the sub-frame is bolted. I also used a strap from the transmission mount to the subframe because I didn't have a 2nd threaded rod set-up. I tightened this strap and the threaded rod until the sub-frame pulled backwards enough for the studs to line up with holes in the frame and then bolted everything back together.

Although my old top-mounts were not torn the difference in the car is really noticeable, as I had hoped it would be. The kick-back in the steering over any kind of bumps is finally gone and the ride is terrific. I had avoided this job for a long time because I thought it would be too hard to do but I was never happy with the amount of kick-back in the steering wheel. Now I enjoy driving the car so much more and with the short cuts the whole job is far easier.

 

Followed the same procedure for my replacement today. Only thing that threw me off was the step to undo the 4 bolts holding the subframe to the body - I was crawling all over under the car trying to figure out what bolts, until finally realizing those were the 2 bolts on each side, for the subframe bushing down from the top. Only hard part of the job is getting the driver onto to the rear bolts of the bushings, just because of the angle and tight confines. The subframe drops farther than I expected though, so once we went down another inch, it was easier to get to. Definitely use some penetrating liquid on the steering rack bolts, and clean them and the openings up before reassembly. Sheered one of the suckers off putting that back on, and almost stripped a 2nd. Hardest part of the job, right there.

 

I know this was a really old thread but the amount of force it takes to move the subframe back seems silly. My subframe also moved forward about 1/2" and I tried using some 1000lb winch straps and that only got it halfway there. I'm going to try rocklandjag's setup with a spring compressor and a come along. I also made sure the new subframe bushings match up exactly with the old ones. I almost wonder if it would be easier to remove the rear subframe bolts, attach the subframe and engine mounts and then deal with aligning the rear subframe bolt holes.

 

I'm assuming that you got your car all buttoned up (?) I'm in the middle of trying to get my subframe back in position and having a hard time. I've already ruined two come alongs, one by bending the handle and the other got the cable wrapped up in the spool. I still had about a quarter-inch to go before the dowels would line up. Any thoughts on why these things move forward so much? I'm going to give it one more try before I give up and pull the subframe out and do the rear bushings.

 

I ended up removing the rear subframe bolts and then jacking the subframe mounts into place and securing them as well as the motor mounts. I then was able to line up the rear subframe holes and reinsert the bolts. It was much easier this way and the shop manual shows both ways. I did have to use the come alongs and a ratchet extension for fine tuning to line up the bolt holes but overall far easier. I was afraid of damaging the transmission mount and was uncomfortable with the amount of force it was requiring with the other method. So far it seems fine.

 

I think my problem was that I didn't loosen the rear mount bolts before lowering the frame to get to the v-mounts, as I didn't have a 29mm socket. I unbolted the v-mounts with a small trolley jack under each lower wishbone mount bracket, then started letting it down. The left side came down as the v-mount was separated from the rubber, but the right stayed in place. It was quitting time, so left it till the next day, with my big trolley jack positioned a few inches below the front support bar just in case the right side gave way. Went out the next morning and it had released, so I was able to put in the new v-mounts. When trying to pull the frame back in to line up the dowels, I had two come alongs mounted to the trans crossmember then hooked up to the front support bar where it's welded to the frame, so I was pulling each side equally. Like I said, got to about a quarter-inch from getting the dowels lined up and it wouldn't move any farther. That's when I bent the handle on one of the come alongs by using my three-foot breaker bar. I thought that I was getting a good pull, but it was the handle bending 90 degrees. The other side was doing the same thing, so I didn't use the big breaker bar on that come along. But, that one had enough force on it that the cable had slipped under some of the winds and it's trash, too. The 29mm socket arrived in the mail (none of the hardware or auto supply stores around here had one), so now I have the rear mounts loosened, and two new 2-ton come alongs to try again. Hopefully I haven't trashed the rear bushings in the process. I would like to replace them while I'm going through all this, and they have been in there for 18 years and 178k miles, but my suspension tools are somewhere in a storage room and I can't even see the big red roll-around toolbox they're stored in.

I saw in the manual (finally, I was searching for 'front subframe' and they call it the 'crossmember') where it shows locating the v-mounts then the rear mounts. I'm somewhat concerned about doing it this way as my frame moved forward about an inch. And that makes me think that the rear bushings are trash as well as the come alongs. Guess I'll find out when I head out to the garage ...

 

Hispeed, when I read your #12 post, I cringed when you said it went forward an inch. I was thinking your rear bushings were trashed since the metal collar in the middle of the rear bushings are pinched hard against the body via that bolt and you let the front down and hence twisted that bushing. Better to do it now while your still in the subframe tackle mode. I did mine in the 98’ XJR with 250k miles on it 2 years ago. Good luck.

 

I was cringing a lot lately with this operation, and twisting the rubber was my main concern. Before loosening those bolts, the frame only came down about two to three inches, but still too much for comfort. When I trashed the first two come alongs, I figured that the rubber was pretty well twisted and that's what was blocking any more progress. But, I went ahead and tried one more time with the bolts loosened and I got the v-mounts seated. I'm still concerned with the rear bushings, but I'm going to have to wait until the spring to go back in. It's getting to be winter here, the car's been hogging the garage for two months now, and wifey wants her spot in there before her car gets another 10-inch dropping of snow on it. And, I still need to put all of the induction back on the engine. I really don't like having to leave it like this, so I'll see how the ride is and probably not drive too far from home for a while.

 

Look at it this way, if your subframe rear bushings were trash they would likely not offer so much resistance. If they were degraded then it should be easier to force the subframe backwards.

 

Hopefully that's the case as everything is back together now. With the bolts loosened, I was able to see a little more of the bushings. The left one looked fine but the right had a little chunk hanging from what I think is the alignment rib. I was able to get a small needle nose pliers up there and gave it a little pull, but it was still attached so I didn't mess with it anymore. Other than that, the bushing looked fine, too. When I say "looked fine," that's in comparison to pics in other threads on this subject that show the bushings all torn up and stuff hanging out where it's not supposed to be. I'll find out sometime next week when I get the engine put back together.