FAQ: Engine/Transmission Motor Mounts

New to the forum .Just bought a black 99 ,and in process of bringing up to original . Body is straight. New struts, shock and tires added ,new leather of front seats ,replaced tranny mount, but can't seem to find front motor mounts. Have read the posts about hockey pucks and polystyrenes ,but are there no new parts available for this anaimal ? Any help is appreciated . DB

Are you talking about the big motor mount on the passenger side that connects to the giant bracket or the mount on the cradle on the driver side (front)?

That front mount is still available. It's listed as a transmission mount (it connects to the tranny). The right engine mount is discontinued from GM, and I haven't found it anywhere aftermarket. I'm going to have to make one soon, as mine is blown out.

Yes the front one is what I am trying to find. Ordered a body mount from partsgeek ,but that's not it .It the one that looks like a puck ,attatches to front cross member in back of radiator.

 https://rivperformance.editboard.com/t2586-write-up-hockey-puck-casting-front-side-motor-mounts

dbs99riv wrote:

Yes the front one is what I am trying to find. Ordered a body mount from partsgeek ,but that's not it .It the one that looks like a puck ,attatches to front cross member in back of radiator.

This mount?

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Automatic-Transmission-Mount/_/R-BK_6201697_0435154918

No the flatter one that they are using hockey pucks to replace /modify .

Your '99 Riviera doesn't have that type of mount. It has the exact mount that I posted for you. You will need a Bonneville trans mount bracket in order to perform that mod.

it is exactly like the puck one. It has almost completely separated and I put a c-clamp on it to prevent movement while I located a replacement. It mount to the transmission brcket with three bolts and them rests flat on the frame cross member.

Really? Weird. I thought all Rivs had that "C" mount like I posted.

Checked gm parts catalog on their site and they show your combo for yrs 95-99 , but my rear mount is different too. Got it on amazon ."Anchor 2898 Trans Mount Left Rear " . So what year were they using the puck mod on the front one for .I couldn't tell from the thread ?

My car is having odd vibrations accelerating and decelerating.  I know the shop said I could use new motor and tranny mounts but I'd like to see pics of them if anyone has them. It would help a lot.

Also,  my problem is weird.  My step dad said there's a pinhole leak in the diaphragm to my boost control bypass valve in the supercharger. I wouldn't think a pinhole leak in that valve when its moving pretty quick should be doing what its doing.

Whats happening is if its like not warmed up in park,  if I make a quick shallow jab at the throttle,  the engine chokes for a second,  shakes really really bad and sometimes stalls.  When the bypass valve had the vacuum line taken out and a belt stuffed in the vacuum line,  my dad was driving it and let off the gas,  then I heard a weird airflow sound followed by lots of engine or tranny rattle,  and the whole car shook really bad. Its not as bad with the bypass valve hooked up right but is more a slight version of that sometimes accelerating lile barely there. Also when I see that happen in park,  the lights dim which really worries me.

Personally I think the engine mounts are bad,  possibly the tranny as well,  and everything else is conjecture.

Thinks I did notice over the past few months:

Slight transmission fluid leak after my car hit abspeed bum,  at least it was red slightly slimy thin fluid that dropped under the tranny but my step dad told me it could be a different issue. Lile power steering fluid  My coolant was green at the time,  and my transmission was acting funny lile hard shifting and if I went WOT some times it would act like my tranny had a rev limiter on it bouncing which shook the car violently

Something else:

When my supercharger belt came off,  I saw a lot of milky thick whitish yellow grease all around it which makes me think some kind of deal busted in the supercharger and it needs an overhaul.  

Theres a sound from the air filter that sounds like a really bad free wheeling pulley or busted ac compressor which makes me thing that something is wrong internally wrong in the supercharger but its really hard to tell with the engine noise in the backround if its weird airflow too. Also the supercharger rattles a little and I can feel play andboscilations in it when I put my habd on the snout but its slight and not violent.

Something else:  

Maybe my transmission torque converter is eating a shit?

Maybe it could simply be a vacuum problem and the MAF is confused as well as other bad sensors maybe amd the engine freaks out,  changes rpm really weird in gear and the oscilations screw with the alignment of the engine hooked up to the tranny?  I mean I saw the engine jerkback and forth like an in of travel in either direction (think 1 inch speaker xmax if that helps)

The supercharger doesnt seem terribly weird idling and it acts mostly normal and the problem is intermittent and waybworse before the engine warms up.. Maybe bad temp senors?

One reason I considered a vacuum problem and bad sensors is the possibility of my transmission and supercharger both acting funny together because my 96 buick has a 4t60-e and I know its vacuum controlled. If that were the case and the bypass vacuum line blocked off would cause the issue decelerating while the vacuum line hooked up right will cause the issue accelerating,  then dim at least my interior lighting is because of maybe a bad ground causing different sensors to cross talk,  then the engine stalls bad,  freaks out,  bad motor mounts and tranny mounts dont help then either? i also do have speaker buzzing also changing from park to reverse is notnsmooth at all.  It has to think for a couple seconds and make strange noises,  idle weird and bump rpm then it decides to shift fine.

Actual gear shifting though when its not acting up is really smooth,  and the underlying engine sound,  especially the exhaust note since the engine tune up and brand new exhaust hangers sounds better than I've ever heard either buick and it sounds far more refine in the exhaust note.

You guys might think this is really stupid but instead of molding my own polyeurothane engine/tranny mpunts, I decided to go with contact cement because its really hard but flexible and probably absorbs vibration and shock much better than poly because its comprised of a lot of santoprene rubber which I know for a fact make the best subwoofer surrounds technology can make right now.  I know that korean bow makers currently use contact cement as an adhesive for layering the wood in their bows.  Also its used for flying shoe soles,  it can fix leaks in a soccer ball as well. I once used half a tub of contact cement to ghetto fill where plate amplifier used to be on a broken subwoofer to basically seal it up and for a long while before the box cracked from abuse, it was one of the most air tight and rattle free,  as well as best woofer controlled subwoofers I've ever heard for such cheap stiff shallow mount subs.  I noticed it was kind of flexible more so than epoxy but still really hard like sap.

I think it may be worth a try before buying new mounts since its a damn near free mod if I can get some time and the right equipment to get at them.

Sorry for overthinking but I wanted to be thorough.

Also in gunna take the diaphragm out of my M62 bypass valve and put it in the m90 if just the diaphragm fits.

My car is mostly sorted out other than the hesitation/extreme engime/tranny shaking.  Any help would be nice,  and I hope my conact cement idea isn't stupid.. It would be a super fast easy way to mold custom bushings using a mold and wd-40 release agent and it cures pretty quick and I think it'd be a perfect balance between ride comfort and firmness for a launch,  and maybe attach it with a medium layer of spongier softer rubber cement if the vibrations are as bad as poly but I seriously doubt vibrations will go through because of my experience using it with that subwoofer and the really ghetto box had 0 weird vibrations at all when I used contact cement to fix a shoddy job when gorilla glue and screws made it rattle like hell to attach a big piece of plywood the same size as the subwoofer under it. I have high hopes for it as an alternative mount and bashing custom diy mold technique but I don't know a lot about the mounts  yet

EDIT:   I apologize for the bad layout,  bad typos and slightly botched run on sentence grammar structure but I typed it on my phone in a hurry and I'll try to clean up the post more tomorrow.

EDIT again:

Santoprene can have a durometer of between 35 A to 60 Shore D hardness and using my finger nail, it felt harder than a roller blade wheel which is apparently is harder than tire tread, operating temps for continues use are up to 135C, extreme wear resistant to hot cold. Changes, extreme wear resistant to most chemicals as well. I have high hopes for this material for a ghetto diy engine mount lol. I don't know why I couldnt more info about contact cement properties.

I wish I could have a durometer test of contact cement and vibration qualities.

https://rivperformance.editboard.com/t882-faq-engine-transmission-motor-mounts

Check this write up out.  I'm also replacing the front and rear trans mounts at the moment.  I filled the gaps in with window weld already about 5 days ago so I'm waiting for it to cure fully.  I'm in the middle of a subframe swap and started replacing whatever I find wrong.

About your supercharger issues, Id say that your snout seal on the supercharger is shot and leaking the supercharger oil. Not terribly difficult of a job. I did mine a while ago along with the coupler replacement. Go to zzperformance.com

Quote :

Also,  my problem is weird.  My step dad said there's a pinhole leak in the diaphragm to my boost control bypass valve in the supercharger. I wouldn't think a pinhole leak in that valve when its moving pretty quick should be doing what its doing.

Whats happening is if its like not warmed up in park,  if I make a quick shallow jab at the throttle,  the engine chokes for a second,  shakes really really bad and sometimes stalls.  When the bypass valve had the vacuum line taken out and a belt stuffed in the vacuum line,  my dad was driving it and let off the gas,  then I heard a weird airflow sound followed by lots of engine or tranny rattle,  and the whole car shook really bad. Its not as bad with the bypass valve hooked up right but is more a slight version of that sometimes accelerating lile barely there. Also when I see that happen in park,  the lights dim which really worries me.

All of this is something related to MAF sensor, vacuum leak, or some other maintenance issue. It has nothing to do with vibration or bad mounts. Research more relavant threads to solve this issue, and/or post a new thread in the appropriate section. Posts in this thread will focus on bad mounts.

Quote :

Slight transmission fluid leak after my car hit abspeed bum,  at least it was red slightly slimy thin fluid that dropped under the tranny but my step dad told me it could be a different issue. Lile power steering fluid  My coolant was green at the time,  and my transmission was acting funny lile hard shifting and if I went WOT some times it would act like my tranny had a rev limiter on it bouncing which shook the car violently

Again, this is unrelated to mounts. Trans fluid leaks can happen in older cars in need if maintenance. Replace the pan gasket for starters. As long as you keep the fluid level correct, your trans should operate fine - unless there's another issue, then it make be rebuild time - good opportunity to inspect and replace the mounts.

me 2

Well, I was able to get the Riv up on the lift today and take a look around. Coming into today, I knew there were four mounts, but only could ever find two of them. I found the rear transmission mount and It's definitely bad!

It's this one here: http://www.rockauto.com/catalog/moreinfo.php?pk=5619906&cc=1303322

How difficult is this one to replace? It looked pretty easy when I was staring at it.

Just so I'm clear with myself, there's four mounts. Three are transmission mounts and one is an engine mount. There's the one engine mount on the passenger side of the vehicle, and one transmission mount at the front of the vehicle. There's also a transmission mount underneath the vehicle. Where's the transmission mount that I'm missing? Is it in the driver side wheel well?

KnottyEagle wrote:

Is it in the driver side wheel well?

Bingo. You have to take out the wheel-well liner in order to see it.

The driver side mount is still original in my car, and I don't know of anyone who's replaced it. Good luck finding one if yours should go bad.

AA wrote:

The driver side mount is still original in my car, and I don't know of anyone who's replaced it. Good luck finding one if yours should go bad.

I tried removing mine when I rebuilt the trans. The studs going through the body were completely frozen and wouldn't even come out with my Air Hammer.....but the mount is still good.

I don't need to remove or replace it. I just didn't know where it was. I'm going to fill the rear mount with polyurethane and replace it. I'm going to either do the same this to the front mount or do the hockey puck thing.

The hockey puck mounting in the front requires a different bracket and some modifications. The Riv isn't designed for that style mount. If you look at the front mount, It's horizontal just like the rear, not vertical. You can simply fill in the front mount just like the rear. That's what I did.

Abaddon wrote:

The hockey puck mounting in the front requires a different bracket and some modifications. The Riv isn't designed for that style mount. If you look at the front mount, It's horizontal just like the rear, not vertical. You can simply fill in the front mount just like the rear. That's what I did.

Hmm, I forgot about the different bracket. I'll just do the polyurethane filling. It'll be easier, and after doing my LIM gasket, I don't really feel like making my own mount.

Abaddon wrote:

The hockey puck mounting in the front requires a different bracket and some modifications. The Riv isn't designed for that style mount. If you look at the front mount, It's horizontal just like the rear, not vertical. You can simply fill in the front mount just like the rear.

No, you're thinking about the old way of doing it. I used 2 pucks with the OEM mount, worked great. Cheaper and easier than messing around with filling the mount. Here's how you do pucks in the front - the better way, IMO:

https://rivperformance.editboard.com/t2586p120-write-up-hockey-puck-casting-front-side-motor-mounts

Ah. You're right. I was actually thinking about the post that Matt put down on the Bonne forum. I also remember a thread on here about buying the Bonne bracket and modifying the cradle for it. I like your mount btw. I've been thinking about ideas on how I want to stiffen up all the mounts when the '97 starts going together.....