How to go about Replacing Rear Transmission Motor Mount

broke_collegekid

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So I ordered my oem rear mount since replacing just the front left one didn't solve 100% of my issue with the jerky gear shifting and vibration on acceleration. How can I go about replacing the rear mount in the simplest way.

I've come across a couple different methods, including this video which involves disconnecting the axle/strut assemblies, dropping the subframe, and then removing the mount.

I've also come across another comment on here that claimed disconnecting the sway bar links and moving the sway bar back would free up enough space.

Any opinions? I have a floor jack and a pair of jack stands but can get more if needed. Really trying to avoid bringing this to my mechanic as I love to DIY things
 

imidazol97

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I did the rear mount replacement and it didn't help a thing. I had replaced the front mount.

It was a terror to replace with the car on jackstands and my shadetree mechanic neighbor doing
the real work. I suspect you'll find replacing the side mounts more helpful if there's something
you can see wrong with them.
 

broke_collegekid

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I did the rear mount replacement and it didn't help a thing. I had replaced the front mount.

It was a terror to replace with the car on jackstands and my shadetree mechanic neighbor doing
the real work. I suspect you'll find replacing the side mounts more helpful if there's something
you can see wrong with them.
ok, will try the side ones first then. Any brands you recommend?
 

imidazol97

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Can you see something wrong with any of the mounts? Tears? Rot. Extra movement when the engine is torqued in place with someone watching who knows how much give is right for the 3800 and the model year you have?

I had a 2003 with 150K miles and more. The front mount was weakened and torn IIRC. My shadetree friend has long experience with 3800s and he felt the rear might be a problem. But he had to squeeze it in after barely getting the old one out. The side mounts showed no problems.

We replaced the half shafts. One was badly worn. But still the engine had vibration and what seemed to be uneven
acceleration while turning a corner. I realized it may just be the aged beast and I couldn't fix it.

My thoughts after reading more people here having problems is it might have been related to changing the struts. I used quick struts the second time and it changed the alignment because the springs were different heights. I should have just bought new springs and stayed with the original style strut.

I wonder if the change in height and adapting the alignment to what the new struts were changed the way the tires
are turned a different number of degrees to accomodate the different radii of the two front wheels when going around a corner. The inaccuracy in the turning angle (there's an alignment name for the angle, but I didn't try to look it up) makes the two front wheels fight each other and I suspect that's felt as the unevenness in the acceleration going around a corner.

This is my theory. But if you can't see there's a problem with one of the mounts, I wouldn't change it. I wasted a lot of effort on my buddy's part over the rear mount. I don't think it was a problem.
______________________________
 

broke_collegekid

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Can you see something wrong with any of the mounts? Tears? Rot. Extra movement when the engine is torqued in place with someone watching who knows how much give is right for the 3800 and the model year you have?

I had a 2003 with 150K miles and more. The front mount was weakened and torn IIRC. My shadetree friend has long experience with 3800s and he felt the rear might be a problem. But he had to squeeze it in after barely getting the old one out. The side mounts showed no problems.

We replaced the half shafts. One was badly worn. But still the engine had vibration and what seemed to be uneven
acceleration while turning a corner. I realized it may just be the aged beast and I couldn't fix it.

My thoughts after reading more people here having problems is it might have been related to changing the struts. I used quick struts the second time and it changed the alignment because the springs were different heights. I should have just bought new springs and stayed with the original style strut.

I wonder if the change in height and adapting the alignment to what the new struts were changed the way the tires
are turned a different number of degrees to accomodate the different radii of the two front wheels when going around a corner. The inaccuracy in the turning angle (there's an alignment name for the angle, but I didn't try to look it up) makes the two front wheels fight each other and I suspect that's felt as the unevenness in the acceleration going around a corner.

This is my theory. But if you can't see there's a problem with one of the mounts, I wouldn't change it. I wasted a lot of effort on my buddy's part over the rear mount. I don't think it was a problem.
Yeah I do have some rather cheap quick struts in there lol. I do have my original springs and am still contemplating possibly putting the old ones back in.

I do get somewhat still harsh transmission shifts especially if I’m coasting on the highway and suddenly step on it, there’s a big jerk upon acceleration that makes me think the rear ended of the transmission is a bit loose. But I’ll run a couple of those motor torque tests and really inspect all the mounts this weekend and report back here.
 

imidazol97

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If you have a friend to help while you watch the movement of the engine at the 4 corners while the
trans is shifted in different forward backward modes, I'd have to see real movement and then be able to
see that mount has softened or torn. I guess I'm say we wasted time and energy doing the rear mount on my car. Yours might be different.

I'd also suggest that you find someone with a similar H-body to yours with lots less miles and look at the
movement it makes when being shifted and lightly stressed. They do move around, but I suspect you'll see a difference.

My strut story is I changed them at home and tried to reposition the holes about where the original replacement Monroes were, which made the replacements close in alignment. I drove the car to a Buick dealer who aligned it but never said it was difficult to get the camber right. I _think_ he did the camber by having both sides positive but equal to avoid a lead problem.

Later after hitting the interstate pothole, I had the car realigned at the Chevy dealer owned by the same guy
as the Buick store. The good alignment guy there had trouble and had to get wobble bolts shipped in to be able to do the job. ORiginally the car only had 1 wobble bolt on the struts from when the car had hit another Ohio interstate pothole years earlier.
 

Frampton

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If you have a friend to help while you watch the movement of the engine at the 4 corners while the
trans is shifted in different forward backward modes, I'd have to see real movement and then be able to
see that mount has softened or torn. I guess I'm say we wasted time and energy doing the rear mount on my car. Yours might be different.

I'd also suggest that you find someone with a similar H-body to yours with lots less miles and look at the
movement it makes when being shifted and lightly stressed. They do move around, but I suspect you'll see a difference.

My strut story is I changed them at home and tried to reposition the holes about where the original replacement Monroes were, which made the replacements close in alignment. I drove the car to a Buick dealer who aligned it but never said it was difficult to get the camber right. I _think_ he did the camber by having both sides positive but equal to avoid a lead problem.

Later after hitting the interstate pothole, I had the car realigned at the Chevy dealer owned by the same guy
as the Buick store. The good alignment guy there had trouble and had to get wobble bolts shipped in to be able to do the job. ORiginally the car only had 1 wobble bolt on the struts from when the car had hit another Ohio interstate pothole years earlier.
After changing struts or most any suspension part, you need an alignment! Especially struts.
 

broke_collegekid

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After changing struts or most any suspension part, you need an alignment! Especially struts.
I did get an alignment but now again (after about 5000 miles of driving) my car drifts to the left if I hold the steering wheel straight so for whatever reason my alignment could be off. Don't know why. Any sort of explanation? I've hit some potholes and stuff driving in the city but nothing that seemed to have an immediate effect. Both outer tie rods and control arms are 5000 miles new and went in right before alignment. Might go to one of these free alignment check shops
______________________________
 

Ameri

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Yeah I do have some rather cheap quick struts in there lol. I do have my original springs and am still contemplating possibly putting the old ones back in.

I do get somewhat still harsh transmission shifts especially if I’m coasting on the highway and suddenly step on it, there’s a big jerk upon acceleration that makes me think the rear ended of the transmission is a bit loose. But I’ll run a couple of those motor torque tests and really inspect all the mounts this weekend and report back here.
OP,
I am curious to know too. Last year I replaced all 4 trans mounts, front struts, and strut mounts, and have been feeling vibration in the cabin. All parts were OEM.
 

broke_collegekid

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OP,
I am curious to know too. Last year I replaced all 4 trans mounts, front struts, and strut mounts, and have been feeling vibration in the cabin. All parts were OEM.
Interesting! I got new struts and just a new front mount, other 3 mounts are stock. I haven't replaced anything yet despite having the rear mount sitting in my parents garage because I'm gonna order some of the cheap hydraulic ones for either side and do those first, since they are easier to do. I'll let you know if that helps. What brand struts and mounts did you use?
 

Ameri

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Interesting! I got new struts and just a new front mount, other 3 mounts are stock. I haven't replaced anything yet despite having the rear mount sitting in my parents garage because I'm gonna order some of the cheap hydraulic ones for either side and do those first, since they are easier to do. I'll let you know if that helps. What brand struts and mounts did you use?

I did use supposedly "OEM" strut mounts part number 19208376, and struts part number 22064781. The struts aren't that great really. I am not sure though if it is the struts that are bad, or the new strut bearing design not jiving well with the struts. Check out my post about that last year:

 

broke_collegekid

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I did use supposedly "OEM" strut mounts part number 19208376, and struts part number 22064781. The struts aren't that great really. I am not sure though if it is the struts that are bad, or the new strut bearing design not jiving well with the struts. Check out my post about that last year:

I just ordered 2 really cheap left & right motor mounts from Rock Auto. I'm gonna buy some poly and fill the gaps in those mounts as well to support them some more if possible and I'll post in this forum once I do that. Would be a cheap way to make those really unreliable mounts last if I can pull it off.

When do you feel vibration in the cabin? At idle? If so its gotta be the mounts then. If driving and you get it even with your foot off the gas at whatever speed its probably suspension. I bought the cheap $60 each FCS quick strut assemblies from rock auto and my car rides like it has some sort of sport suspension now and i take a beating when driving on poor city roads.
______________________________
 

Frampton

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I just ordered 2 really cheap left & right motor mounts from Rock Auto. I'm gonna buy some poly and fill the gaps in those mounts as well to support them some more if possible and I'll post in this forum once I do that. Would be a cheap way to make those really unreliable mounts last if I can pull it off.

When do you feel vibration in the cabin? At idle? If so its gotta be the mounts then. If driving and you get it even with your foot off the gas at whatever speed its probably suspension. I bought the cheap $60 each FCS quick strut assemblies from rock auto and my car rides like it has some sort of sport suspension now and i take a beating when driving on poor city roads.
Be careful, there should be SOME movement in the mounts.
 

Ameri

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I just ordered 2 really cheap left & right motor mounts from Rock Auto. I'm gonna buy some poly and fill the gaps in those mounts as well to support them some more if possible and I'll post in this forum once I do that. Would be a cheap way to make those really unreliable mounts last if I can pull it off.

When do you feel vibration in the cabin? At idle? If so its gotta be the mounts then. If driving and you get it even with your foot off the gas at whatever speed its probably suspension. I bought the cheap $60 each FCS quick strut assemblies from rock auto and my car rides like it has some sort of sport suspension now and i take a beating when driving on poor city roads.

Cheap mounts are not necessarily unreliable, solid option can actually be quite reliable but will transmit serious vibrations to the cabin.

I certainly hear clunk and feel certain road imperfections due to a very soft front struts. However, I still feel some vibrations at idle or when I increase engine speed, which makes me think about engine mounts or possibly another component.
 

Frampton

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Cheap mounts are not necessarily unreliable, solid option can actually be quite reliable but will transmit serious vibrations to the cabin.

I certainly hear clunk and feel certain road imperfections due to a very soft front struts. However, I still feel some vibrations at idle or when I increase engine speed, which makes me think about engine mounts or possibly another component.
How many miles on your car?
 

Frampton

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Now I am at 140 K.
There's a place called northstarperformance.com who makes they're own version of the frt left trans mount. Lifetime warranty and is a permanent fix for that mount. Check it out. Expensive but the last one you'll buy.
 

Ameri

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There's a place called northstarperformance.com who makes they're own version of the frt left trans mount. Lifetime warranty and is a permanent fix for that mount. Check it out. Expensive but the last one you'll buy.
Thank you for sharing this information. This version however can potentially increase vibrations.
 

broke_collegekid

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Thank you for sharing this information. This version however can potentially increase vibrations.
For that price and what you'd get you might as well try the hockey puck motor mount mod. Basically the same thing in terms of the vibrations you'd probably get. I'm gonna mess around with that mod and make a new thread once I finish it. Same goes for adding some poly to the left & right mounts in each wheel well.
 

Frampton

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For that price and what you'd get you might as well try the hockey puck motor mount mod. Basically the same thing in terms of the vibrations you'd probably get. I'm gonna mess around with that mod and make a new thread once I finish it. Same goes for adding some poly to the left & right mounts in each wheel well.
Don't know about the mods your referring to. Can't you explain? Idk about feeling any vibrations. I don't with my car.
 

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