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transmission and motor mounts

R

Rod Knee

NAXJA Forum User
Location
Grand Jct., CO
I recently installed a zj fan clutch into my xj. Its pretty tight in there with the cfs 3 row radiator and I have been reading up on options for upgrading my motor mounts and transmission mount. All three of my mounts are stock but in good shape. From what I gather from reading and simple visual inspection of the parts the transmission mount is a more substantial piece than the motor mounts.

So I am wondering if the transmission mount is subject to the same sort of sudden failure as the motor mounts are. I plan on getting the rubber Brown Dog motor mounts, but I’m not so sure I need to replace a trans. mount that is in good shape.
 
I thought my tranny mount was in reasonably good shape, but decided to replace it when I did motor mounts, just because I was dealing with that system.

Here are a couple of pics:



TrannyMount1OPT.jpg


Yeah, it has a couple of cracks, but how bad could those be?


TrannyMount2OPT.jpg



Hmm...

It's kind of tough to get a good look at that mount until you pull it out.

You will have to decide for yourself.
 
Anak said:
Hmm...
It's kind of tough to get a good look at that mount until you pull it out.
You will have to decide for yourself.
Click to expand...

I have seen more bad transmission mounts than motor mounts. You really cannot see how bad one is without removing it, a PIA to check.
It's also hard to find a decent OEM type mount, all the replacements are either junk from China or India.
2000-2001 XJs use a different rear mount and its just about impossible to find the correct one, it's easier and cheaper to re-drill the cross member to accommodate the newer mount's offset bolt holes.
Tried a poly transmission replacements but it the added noise and vibrations was too extreme.

Used Brown Dog mounts for two years before giving up on using them on my DD. The noise and vibrations is fine for a trail rig or one that isn't driven on the street a lot, but too much for a rig that sees a lot of street and highway miles.
When used with a poly trans mount, you can hear every noise the engine, transmission and transfercase makes.
Did like the feel of the engines' response with the BDs, very solid and well connected to the driveline. I have keep them and re-install them when heading out on week or longer off-road trips, takes about an hour to reinstall.
There is no perfect solution...yet.
 
lazyxj said:
Used Brown Dog mounts for two years before giving up on using them on my DD. The noise and vibrations is fine for a trail rig or one that isn't driven on the street a lot, but too much for a rig that sees a lot of street and highway miles.
When used with a poly trans mount, you can hear every noise the engine, transmission and transfercase makes.
.
Click to expand...

Did/do you have the rubber or poly mounts?
 
For what it is worth, I am running the BrownDog rubber motor mounts and a rubber Napa tranny mount. I have not noticed that the vibration is any worse than what I had with worn out mounts. I use my XJ as a daily driver/family hauler.

OTOH, I am comfortable with my Cummins 12 valve, as well as with my 454 Suburban with a performance cam (not exactly the smoothest at idle). My tolerance level for vibrations may be on the high side.
 
I have been running Brown Dog rubber mounts paired with their super brackets and a new rubber trans mount since May. The only time I noticed vibrations was when idling in drive (sitting at a stop light, etc). I only noticed the vibes for the first week or two. Several thousand miles later, I don't notice any vibes, ever. Follow BDs install instructions and give the mounts time to settle in. You'll be very pleased.
 
Rod Knee said:
Did/do you have the rubber or poly mounts?
Click to expand...
The BDs Have well broken in rubber mounts. They were adjusted and played with for over a year to minimize the noise and vibs.
I like the way they made the Jeep feel, no problems there but both my wife and could hear a lot more engine and drivetrain noises, Ok when off-roading but annoying on long drives. YMMV

A lot depends on how you use your XJ. Mine is DD that is driven mostly on the street but is used frequently off-road. I don't beat it the way I would a trail only or mostly rig. The interior is intact with the whole inner cabin wrapped in sound proofing mat, after fifty years of playing in the dirt, I'm tired of excessive noise. Forty years of working on industrial equipment and around jet aircraft has had an effect too.
The stock mounts are in good shape and get inspected often.
When we plan week or longer desert trips. The BDs can be switched out rather quickly, once you have it down.
 
FWIW, when I replaced my well worn, 175,000 mile trans mount, I slapped a piece of duct tape on one end and pumped the void full of PL polyurethane sealant. I've done this same thing with XJ engine mounts in the past and it reduces the flex in the mount.
 
lazyxj said:
Used Brown Dog mounts for two years before giving up on using them on my DD. The noise and vibrations is fine for a trail rig or one that isn't driven on the street a lot, but too much for a rig that sees a lot of street and highway miles.
When used with a poly trans mount, you can hear every noise the engine, transmission and transfercase makes.
Click to expand...

Thats not the experience i have with my BD rubber mounts. The only extra noise/vibes I have is at idle and that just a little bit of extra rattle from interior parts, which for the most part can be eliminated.
 
lazyxj said:
I have seen more bad transmission mounts than motor mounts. You really cannot see how bad one is without removing it, a PIA to check.
It's also hard to find a decent OEM type mount, all the replacements are either junk from China or India.
2000-2001 XJs use a different rear mount and its just about impossible to find the correct one, it's easier and cheaper to re-drill the cross member to accommodate the newer mount's offset bolt holes.
Tried a poly transmission replacements but it the added noise and vibrations was too extreme.

Used Brown Dog mounts for two years before giving up on using them on my DD. The noise and vibrations is fine for a trail rig or one that isn't driven on the street a lot, but too much for a rig that sees a lot of street and highway miles.
When used with a poly trans mount, you can hear every noise the engine, transmission and transfercase makes.
Did like the feel of the engines' response with the BDs, very solid and well connected to the driveline. I have keep them and re-install them when heading out on week or longer off-road trips, takes about an hour to reinstall.
There is no perfect solution...yet.
Click to expand...


It sounds like you're asking too much of them.

That poly trans mount really is a huge problem. We went back to autozone transmission mounts.
 
I've heard of the poly transmission mounts being a major pain.

Also, you don't want to run a poly transmission mount without poly engine mounts. E.g. no poly transmission mount with rubber engine mounts.
 
I'm thinking its better to have rubber all around to achieve as much vibration dampening as possible. However, I called Brown Dog and what was recommended was Prothane brand trans. mounts which are poly. I had indicated that my primary interest was assuring my rad. clutch fan would not impinge upon my radiator in an offroad situation, so my inference from that recommendation was that the poly trans. mounts stabilize the transmission/engine better than the stock rubber trans. mounts.

Interestingly, he also expressed the opinion that the transmission mount plays more of a role in keeping the fan out of the radiator than do the motor mounts, which is a suggestion I am having a little bit of trouble wrapping my brain around. But...what do I know?
 
Ok, in thinking about it a bit more and from reading xjeepers response, I'm thinking that the guy at Brown Dog I spoke to was suggesting the poly mounts are less prone to collapse...
 
Rod Knee said:
I recently installed a zj fan clutch into my xj. Its pretty tight in there with the cfs 3 row radiator and I have been reading up on options for upgrading my motor mounts and transmission mount. All three of my mounts are stock but in good shape. From what I gather from reading and simple visual inspection of the parts the transmission mount is a more substantial piece than the motor mounts.

So I am wondering if the transmission mount is subject to the same sort of sudden failure as the motor mounts are. I plan on getting the rubber Brown Dog motor mounts, but I’m not so sure I need to replace a trans. mount that is in good shape.
Click to expand...

You should be loosening the trans mount to install the motor mounts anyway. You can't really see the condition of the trans mount until you pull it. A worn trans mount will put more stress on your brand new motor mounts. Given that, it's best to just change it with the motor mounts.
 
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