Dropping Front Diff for Motor Mounts

[corsair231]

Hey guys, trying to do driver's side motor mount on my Sy. I need more room. I've read that you can drop the diff to get more room without taking it all the way out. In fact I read where someone referenced just 4 bolts. Seems too good to be true but like everything on these infernal creatures it's probably much more complicated than that. As always, my searches come up with nothing or years old threads with no pics anymore. Anyone got a write up and/or pics of the bolts/process. Borrowing someone's garage to do this so the quicker I can get this done the better.
Thanks

 

[graham1524]

Removing the diff with the engine in is a nightmare. Each side has 2 bolts, which are pretty easy to remove (I think they're all 18mm). If you take the front bumper off and loosen everything on the steering linkage it opens up a lot of space. This will be the steering box (3 bolts through the frame) and pitman arm on the passenger side (2 bolts through the frame). Once you disconnect that push them as far forward as you can, you will have to bend a hard brake line just a little bit.

Actually getting the diff out sucks because there is no room to move it easily, the lower mount on the drivers side can be bent to make the process easier but you may break the weld and have to reweld it once its back together. Once you get to that point you will have to turn and manipulate it until you can get it free. I forget exactly how but if you lift or lower the passenger side and rotate it will come out.

Hope that helps

 

[DaveP's Ghost]

The Service Manual says to remove the core support to frame and body to frame bolts and jack the body up off the frame. This allows the engine to be lifted higher. I've done this, I go up about 2" at the mount under the A-pillar, it really helps a lot. On a Ty be careful of the front fender arches getting caught under the bumper when you lift the body. We cracked one of Jason's arches lifting the body and not paying attention. If you are only accessing the 3 bolts between the mount and the block, go in through the wheel well. Take the tire off and inner fender out.

If you are trying to access the bolts between the mount pad and the frame, good luck. The only time I had these bolts out, I also had the lower A-arms off. I don't think the diff has anything to do with accessing the pad to frame bolts.

I would say motor mounts are one of the fussiest things on a SyTy. They are a bitch. Solids are even worse because they don't self-index. Difficult to get them installed with the bolts lined up, and no stresses. I've installed two sets of solids. Both trucks broke the mounts or the bolts fell out within 6 months of daily driving. Too much stress, and a weak designed part.

One more thought for the driver's side: Remove the exhaust manifold and do the mount from the top. Other than the power steer pump bracket (which requires removing the pulley to access the pump bolts) this is pretty straight forward. Just remember to put the big bolt back in from rear to front (the nut goes on the front). If you put it in from front to rear, and in the future have to R&R the engine for some reason, you'll be pulling the manifold first to get the bolt out. (Found this on a Sy I took the engine out of. Added an hour and a half to a one hour task.)

 

[wildphil]

The last motor mount I changed was on a Syclone. I used one of Jeff's new solid mounts. It went in easily. The only thins I removed were the wheel and inner fender well. I took the transmission mount loose so the engine could be raised with a jack. I have never had to unbolt the body from the frame or remove any of the steering on any of the SyTy motor mounts that I have replaced. That would be a lot of work.

You can gain a bit more room if needed by removing the upper bolt on the front differential and the two bolts on the driver side axel tube. You can use a jack to lower and raise it as needed. I can't remember if the front drive shaft needs to be removed or not. This does not have to be done to replace the mount. It took less than one hour to do the last driver side mount that I replaced. I would not use a stock rubber mount. I destroyed a new one by doing one boost launch.

 

[corsair231]

Thanks Phil, that encourages me a lot because looking at the other posts I was seriously considering my next purchase to be a gallon of gas and some matches. But then again less than an hour? How the hades? Was the engine already out of the truck? But seriously, did you have to take off the frame mount or were you able to get enough clearance to just pull the block side mount and was this with or without dropping the diff? Any other tricks you'd like to share? I had heard about slotting the mount so you can start the bottom bolt and just slide the mount on and then start the top bolts but idk about that, sounds a little iffy to me. I have stock rubber mounts but I was planning on reinforcing it with a bolt through the mount to help limit travel.

 

[1blkc4]

I used these from what I remember I removed both wheel wells , front bumper along with the intercooler and steering box along with an engine hoist https://jagsthatrun.com/collections...ment-mounts-for-1988-2004-s-10-trucks-blazers

 

[DaveP's Ghost]

The deal with having to lift the body is if you are working with the STOCK rubber mounts. If you don't lift the body, you can't lift the engine far enough to get a socket or anything in to the lower bolt because it is only about 3/4" away from the pad. The bottom bolt is recessed inside the mount. Youcan't get a wrench on it. Has to be a socket.

Now. If the old rubber mount is split in two, no problem to get the old one off the block because you can use a box wrench. Same with installing the solid to the block. Use a box-end.

There are no suitable replacement 4.3 rubber mounts any longer. GM is discontinued, and the "Anchor Brand" from China lasted less than a week before it broke, and I installed the JSMs. Oh, and: The truck DOES vibrate. It is NOTICEABLY harsher at idle in gear. (I put it in Neutral at a light). I remember back in the day asking about harshness with solid mounts, and the consensus was "No difference." "I can't feel a thing". I thought it was BS than, and I know it is now. Solid mounts DO make a stock street Ty harsher to live with.

 

[wildphil]

Your rubber mounts are going to be much harder to work with than solid mounts. Like Dave has stated getting wrenches and sockets on them is not easy the rubber covers the bolts.

The first set I did with engine in the truck was a Ty. It was the solids that took the RPM frame mounts. Replaced both mounts. They sucked and the install was very hard. It took probably 6 hours. I did not have to raise the body. I think that I did lower the front differential. The latest solid mounts that Jeff Scott made make installation much easier and the stock SyTy frame mounts work for them also. Looks like Dave does not care for them at all.

Everything I am saying is from memory and my memory is not the best. I usually have to tear into things and then I remember the tricks that I used if I have done the task before. Many things are not by the book. I remove the trans mount. You have to jack the trans up to remove the mount but leave the trans connected to the engine. Then you can jack the engine up to remove and replace the motor mount. If I remember correctly you may have to leave the bolts loose enough on the engine mount so the mount can be moved a bit to get the through bolt in. Then tighten all engine mount bolts. If you leave a rubber mount on one side and replace the side that lifts up with torque it vibrates less than both solid mounts. When the trans mount is reinstalled. It needs to be jacked up for clearance then the bolts installed loose enough so when the trans is lowered the mount can be moved as needed to drop into the holes in the crossmember.

I never drove a truck that many miles after using solid mounts to see how well they held up. From Dave's experience with solids they do not hold up well.

 

[neildemo]

The deal with having to lift the body is if you are working with the STOCK rubber mounts. If you don't lift the body, you can't lift the engine far enough to get a socket or anything in to the lower bolt because it is only about 3/4" away from the pad. The bottom bolt is recessed inside the mount. Youcan't get a wrench on it. Has to be a socket.

Now. If the old rubber mount is split in two, no problem to get the old one off the block because you can use a box wrench. Same with installing the solid to the block. Use a box-end.

There are no suitable replacement 4.3 rubber mounts any longer. GM is discontinued, and the "Anchor Brand" from China lasted less than a week before it broke, and I installed the JSMs. Oh, and: The truck DOES vibrate. It is NOTICEABLY harsher at idle in gear. (I put it in Neutral at a light). I remember back in the day asking about harshness with solid mounts, and the consensus was "No difference." "I can't feel a thing". I thought it was BS than, and I know it is now. Solid mounts DO make a stock street Ty harsher to live with.

Great info! thanks for sharing.

 

[DaveP's Ghost]

Pics are better than words:

 

[wildphil]

^^^^^ Yes Dave that does say it all.

 

[syclone809]

Pics are better than words:

Hi Dave,
What was JSM's response to the pic/design flaws? I recently purchased a set of these before I knew all this info. Thanks

Adam

 

[neildemo]

Cheap Metal and Poor Welds my Guess. Dave Could def Tell us the root Cause as he is a Rocket Scientist/ Engineer .

 

[wildphil]

I am pretty surprised that they break at all. But what do I know? I wonder if welding additional metal stock on the inside of that break location would be sufficient to strengthen the mount enough to be good? I person would want to be pretty sure about the part holding up before they went through all of the work it takes to install it though.

 

[DaveP's Ghost]

And when it breaks, the engine drops down. The fan chews up the lower radiator shroud. I'm not sure what the owner did to get it back to his shop where he could deal with it. He may have had it flatbedded. He re-welded the broken mount and reinstalled it.




The root cause of the breakage is that it is very difficult to install the engine without a lot of bending stress on the mounts, because nothing "indexes", the bolts go in where they go in, and just a bit off, and the mount is under stress. It will fracture, that's what steel does. A secondary factor is the way the mount is fabbed: It is a single piece, scored about 1/2 way through, bent 90deg, and the outside of the bend where it was scored is welded. Looking at the one in the pic it appears that penetration was inadequate, the metal gauge is probably too thin, and the 'JSM' cut-out makes the section to the one upper bolt too small, and it cracks. Then there is only one upper bolt holding the torque. And its section is pretty weak too.

I have a couple of ideas how these could be made more robust, and alleviate the lack of index that causes the stress that breaks them. I doubt I'd ever do anything with making them. I'm surprised that Jeff still makes anything either. The hassles are never-ending. If my solids break before I sell the truck (and it becomes someone else's problem when they do) I'll probably go with the JTR 2.8 adaptations.

 

[DaveP's Ghost]

What was JSM's response to the pic/design flaws? I recently purchased a set of these before I knew all this info.

I haven't talked to Jeff for a long time.

I would suggest you take them to a welding shop and have the welds beefed up on both sides of each bend, and perhaps fill-in the "m" in jSm to make that ear less prone to fracturing.

When you install them, bolt the mounts to the block loosely. When installing the engine, get all the long through-bolts in and fairly snug. Then center the transmission mount on the cross-member, install the trans-to-cross-member bolts so that the trans is centered, then go and tighten the block to mount bolts. It may be really fussy to tighten the block-to-mount bolts after the engine is down, I don't know, I've never done this. But I DO know that it is difficult to get the trans bolts in because the engine mounts will be way off if you just 'bolt them on'. Forcing the trans over to get its bolts in is what places the mounts under the stress that breaks them.

Put in a set of the JTR mounts. Let me know how that goes. That's probably the best solution that is currently available.

 

[corsair231]

I used these from what I remember I removed both wheel wells , front bumper along with the intercooler and steering box along with an engine hoist https://jagsthatrun.com/collections...ment-mounts-for-1988-2004-s-10-trucks-blazers

Were these easy to go on? More clearance than stock? Did you still use the heat shield? The rubber isolator bolts to the frame on these instead of the block right?

 

[Ty1642]

I have the JTR mounts. They require removing both halves of the old mounts (on the motor and on the frame), which is a pain. They are slightly smaller than the stock style mounts. The good thing with these is the rubber isolator is surrounded by steel. The stock mount isolator is bonded to the steel, and when that bonding fails the entire mount comes apart. The JTR mounts can't fail that way, even if the rubber were to crack or split somehow.

 

[wildphil]

I have been looking at those JTR mounts listed. They look like they should work well if everything fits like they need to. All of the work involved in the install is sure a down side.

 

[corsair231]

I have the JTR mounts. They require removing both halves of the old mounts (on the motor and on the frame), which is a pain. They are slightly smaller than the stock style mounts.

I read somewhere that with the JTR mounts the engine sits about an inch higher. Have you noticed that and has it caused any issues?

I have been looking at those JTR mounts listed. They look like they should work well if everything fits like they need to. All of the work involved in the install is sure a down side.

Most people I've talked to said you need to remove the frame mount anyway if you are doing stock mounts. I don't see where these should be any more work than stock mounts.

What I've heard about some people doing is to drill the stock mount and put a bolt through it to limit the amount of travel and keeping the rubber from pulling away from the steel. The only issue with this is there is almost no clearance between the block and frame mount. A standard bolt head will not let the two mounts join correctly. Anyone done this successfully? Will a regular grade 3-5 carriage bolt hold up to the task or will it need to be a grade 8 bolt?