Motor Mount
 

I just rolled 60,000 miles today on my '05 GXP and took the car in for service. Low and behold I have a broken motor mount near the exhaust manifold. The mechanic told me he is seeing a lot of this on the V8 Bonneville's as the miles start to get in my mileage range. The estimate to repair it is $620.00.

Thats insane, do you have a set of jack stands, a jack and basic metric hand tools? If you can find the mount some where I am sure you can change it yourself in an afternoon.

The part will cost you about 75 bucks from gm dealer at cost, takes about two hours to do, been there done that, 40,000 miles, wasn't fully broken but it was rocking around quite a bit, replaced the mount and now it feels like a new car again, the Caddy guys are having the same problems. Save yourself some serious cash and do it your self.

I have owned my GXP for 11 months. I have had two replaced under the dealer warranty. I am now hearing the tell-tale clunk from reverse to drive of my third motor mount. I am NOT running this car hard at all. I ran a 92 Firebird ten times as hard and never had a problem. Some may laugh, but I will find a way to chain that engine down when the repair is my nickel and sweat!

GM part number is 25713699 on my 2004 4.6L N*.

We have seen this here and there since the LD8 went into the Bonne. I wonder if its a hit and miss flaw in manufacturing. Some of us have really put the torque to them and never had a problem. I have always expected mine to fail, but hasn't. 48k pretty hard miles.

I would assume they are the same, but can anyone confirm the that '04 and '05 have the same part number?

Yes. the only difference is on the Title. LOL.

Has anyone come across something other than stock? Something a little more robust?

Not likely given the low number of production. I doubt it. Rockauto doesn't show one.

I have seen some people trying to put something together on the Cadillac Forum for a aftermarket style motor mount, but have not been there for a while to check it out to see if there is any new info. Some other info is that I have seen a 2006 Buick Lucern with a 4.6 installed and it had some quite interesting bracing from the front side of the motor, looks like a factory fix for the motor mount failure problem.

Northstar Performance has a solid mount for the Cadillacs. Not sure how it would work in a GXP.

Motor mount
 

According to GM Direct this is the part number for the 3.8.


The number for the N* is 25759455

I also checked AllData and it confirmed that 25759455 is the mount for the N*.

A good point Mike, and we have seen it alot in Auto stores and catalogs. They just dont seem to get we have a V8. Always good to cross reference online to check, and look at what your getting before you take a part home locally. It has gotten better since the beginning.

http://www.compnine.com/largeimg/9904216K00-004.gif

25759455 = Front Engine mount

25695932 = Transmission mount

25705786 = Trans/Engine rear mount

25710672 = Pass Side engine mount w/o absorber, channel, & bolt

25713699 = Pass Side engine mount W/ absorber, channel & bolt.




My question is, WHICH one is the one that normally goes bad?

Is there a way to visually inspect the mount itself?

I had the hood up and ran the engine up against the brake in fwd and reverse, and do have some movement, but without anything to compare it to, I don't know if it's TOO much movement or the normal/accepted amount.

It would seem like the front mount would be the one to take the most abuse as it's getting pulled apart each time you accelerate. The rear would only get compressed and should last longer......correct?

Any suggestions?

Thanks,
Ken

I don't know of one person here Ken thats actually replaced one themselves. (someone of the past might come in and refute that, never know) but of what I remember, all were done by the Dealer. The best description I remember of past threads, (our Forum search engine works) You are correct in that it is the front motor mount prone to fail, and the best description I have read is a definitive clunk when shifting between 1st and 2nd. As mentioned, there is a little play when reving in gear while stationary. If the mount is broke, that play would be very exagerated when this is done. Its a real PITA that not alot of our drivetrain can't be examined by ourselves without a lift. The car sit so low in the front My ramps only work with this car if I dig gravel out from behind the front wheel and place them there and back the car onto them. Still have a time seeing or doing more than pulling the oil plug and filter. :rolleyes: For me the GMPP has reminded me over and over of it's value.

After just putting the N* in my car the rear mount is a pain in the butt! there is three bolts on the trans mount and they are hard to get in. they are in a shape on a triangle. the top is easy and the bottom driver side is hard but possible and the right one is crazy cause it is behind the steering system. If you really want to know how to do it pm me and I can explain how to do it in detail. I will tell you this... out of the three bolts I could only get two of them on. I had to go to the dealer today to ask them about it and they said two is enough. I am going to have them put the third bolt in and it is gonna run me $46 bucks and I feel it is worth it. moral of the story is if you at least get the two in and have to take it and get the other one put in you are going to save alot of $$$$..

Took my 04 GXP in for an oil change yesterday and they pointed out to me that my front motor mount was broken as well. I have had some vibration in the front of my car for some time now and my Service Stability System light comes on everytime I drive now. A few questions, can this broken motor mount be the cause of my vibration and this Service Stability System light coming on? How hard is this to replace myself? Just FYI, the car has about 155k miles on it and both wheel bearings have been replaced. The front passenger side was def. bad so I changed it. The other one I just changed thinking it was causing the vibration and teh SSS light to come on. Made no difference and I'm thinking it was probably okay all along. Thanks in advance for your help.

My GXP's in the tranny shop right now getting a new tranny. I decided to but the front and rear mounts to replace while they had everything apart.

It's a good thing too. The front mount was in pieces (like I'd suspected, but had been unable to verify) when they took it apart.

Sorry, should have been BUY not but.(above).....

Does anyone know the GM spec on how much travel the N* should have? In otherwords; how much movement is considered nominal at X rpm in drive with brake on. Just got mine back from 2 days at the dealer, doing my end of warranty laundry list. I asked them to check them, referencing similar knock JWANDE spoke of above. Dealer calims they are fine.

Had a ton of other stuff check and done, well over $2,500 worth, all warranty work with only $50 out of pocket deductable. I'll detail later if anyone would like...

There wouldn't be a "Spec" on the travel, but it should be minimal. What the rubber would allow. A broke mount could allow a few inches, if you got on it.

I would be very interested in hearing the details. I have 2 years left on my extended come January but nice to know what to have them look for, outside of the IM shaft, mounts, crossover lines.

I got the tech rep to commit to getting the GM spec. There has got to be one. X ft lb tourque + Y inertia = Z how high should the N* lift?

I'm told the GM OEM is a fluid filled mount and does have a nominal amount of travel from compression.

I replaced my front mount on my GXP about a month ago. ITS A PAIN IN THE A**!!!!!!. No "couple of hours". Its well worth it to figure out how to do it though. When your warranty runs out, 650.00 bucks is alot to spent for a 120.00 part.

I have another 2 years before mine runs out.... Im going to keep an eye on mine!!!

another 16 months and im already writing my list down