Sometimes it's those little things ...

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Like a transmission mount ... 3 years ago, I started to have driveline vibrations, front and rear, on the Cherokee. After some troubleshooting, I determined the front differential suffered pinion bearing failure (pretty common for that differential). I bought a new axle and swapped it in. Helped a bit, but still had some front and back. Then I rebuilt the driveshaft myself and the front was no problem! Had some issues with the rear driveline vibrations. Always seemed to get worse after driving a bit. I did the "typical" Jeep things to get rid of rear driveline vibrations. Did a transfer case drop. Nothing. Then bought SYE kit and a few other goodies and had the transfer case rebuilt. Still had the problem. I figured it was the junkyard shaft that I rebuilt myself. While I have had good luck rebuilding cardan joints in the past, I thought that, maybe, I messed this one up. Brought it to Fleetpride, paid $130 for a rebuilt driveshaft with balance and .... Still bad. I was getting ready to scrap the Jeep by this point. I had been chasing these issues for three years. I missed out on a LOT of off roading trips because I couldn't drive the thing. I figured the differential was bad. I dumped 85w140 gear oil in it to see if that would quiet it down. Surprisingly enough, it did help. Great! So I bought another axle. By then, it started to get winter out and I wasn't really able to swap it. Over the winter, I noticed i started to get a real bad clunking. I figured it was a damaged control arm. A friend noticed it sounded like the transmission was hitting the floor. Sure enough, the transmission was hitting the floor. Started wondering if it was a bad transmission mount that was transmitting driveline vibrations into the cabin? Having had a transmission mount go bad before, it's usually engine speed related issues. Then I had someone brake torque it when I was looking underneath. Couldn't believe it! The transmission mount delaminated; when on the gas, the drivetrain would rock around and throw the driveline angles so far off that it would vibrate horribly. It didn't look terrible with weight on it. Ordered the $30 part from Rock auto. Played around with some stubborn bolts and ... IT FIXED THE ISSUE. 3 years. Over $1K later. And it was a $30 transmission mount. I've managed to put 250 miles on it in one week now. I have to make up for 3 years of not being able to drive it and putting more-than-necessary miles on the car.
 

Nick1994

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Wow, maybe that's one of the issues with the vibration and droning noises with my grandfathers jeep. I put in another rear axle and it didn't help. I'll check the transmission mount today.
 
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Thank you for educating yourself, you are now the BITOG Jeep drive-line expert. Congratulations! Years ago I had a beater that developed starter problems. I replaced the starter, alternator, voltage regulator (separate part back then), some cables, redid grounds, all figuring it wasn't the almost-new battery. I taught myself how to calibrate a relay based voltage regulator on the bench. Finally I replaced the "nearly new" battery and all my starting/charging problems went away. I took with me a knowledge of automobile electronics that serves me well to this day. Years ago I had unexplained bumps and thumps, couldn't figure it out... I was working on another problem, revved the engine by hand (carb) and the V8 practically jumped out of the engine bay. I replaced the engine mount and life got a lot nicer. I guess the lessons are, check the basics first, be observant and patient, and no one is going to spend the time and effort to debug a hidden problem like the owner.
 
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Originally Posted By: Miller88
Like a transmission mount ... The transmission mount delaminated; when on the gas, the drivetrain would rock around and throw the driveline angles so far off that it would vibrate horribly. It didn't look terrible with weight on it. Ordered the $30 part from Rock auto. Played around with some stubborn bolts and ... IT FIXED THE ISSUE. 3 years. Over $1K later. And it was a $30 transmission mount. I've managed to put 250 miles on it in one week now. I have to make up for 3 years of not being able to drive it and putting more-than-necessary miles on the car.
My 15 year old 15x,xxx miles E430 and 9 year old 16x,xxx V70 had engine and transmission mounts replaced last year. Both cars had excessive vibration when shifted to D or R from Park, and moderate vibration when driving, took it to my trusted mechanic he test drove the cars and told all mounts are bad. Parts for each car were less than $100-150 and labor was $250-300. The 21 year old 37x,xxx miles LS400 still has original engine and transmission mounts.
 

SwampSurvivor

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Originally Posted By: HangFire
Thank you for educating yourself, you are now the BITOG Jeep drive-line expert. Congratulations! Years ago I had a beater that developed starter problems. I replaced the starter, alternator, voltage regulator (separate part back then), some cables, redid grounds, all figuring it wasn't the almost-new battery. I taught myself how to calibrate a relay based voltage regulator on the bench. Finally I replaced the "nearly new" battery and all my starting/charging problems went away. I took with me a knowledge of automobile electronics that serves me well to this day. Years ago I had unexplained bumps and thumps, couldn't figure it out... I was working on another problem, revved the engine by hand (carb) and the V8 practically jumped out of the engine bay. I replaced the engine mount and life got a lot nicer. I guess the lessons are, check the basics first, be observant and patient, and no one is going to spend the time and effort to debug a hidden problem like the owner.
I went through something similar a few years ago with the Cherokee. It would crank and crank and crank and crank at it's normal speed before it would start. Then, it would often stall at stoplights and do the same thing. Turns out the battery was bad.
Originally Posted By: Nick1994
Is this the mount above that crossmember under the transmission?
Yup! The bolts for it (18mm) thread through the transmission. Clean them off now and spray with penetrant if you ever want to remove it!
Originally Posted By: HTSS_TR
Originally Posted By: Miller88
Like a transmission mount ... The transmission mount delaminated; when on the gas, the drivetrain would rock around and throw the driveline angles so far off that it would vibrate horribly. It didn't look terrible with weight on it. Ordered the $30 part from Rock auto. Played around with some stubborn bolts and ... IT FIXED THE ISSUE. 3 years. Over $1K later. And it was a $30 transmission mount. I've managed to put 250 miles on it in one week now. I have to make up for 3 years of not being able to drive it and putting more-than-necessary miles on the car.
My 15 year old 15x,xxx miles E430 and 9 year old 16x,xxx V70 had engine and transmission mounts replaced last year. Both cars had excessive vibration when shifted to D or R from Park, and moderate vibration when driving, took it to my trusted mechanic he test drove the cars and told all mounts are bad. Parts for each car were less than $100-150 and labor was $250-300. The 21 year old 37x,xxx miles LS400 still has original engine and transmission mounts.
Could also feel it lurching between directions.
 
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Hello, I helped a friend ready his 'super truck' for sale. 1989 K1500 short bed. It had blown a head gasket. We added headers. We removed the air injector. Bad starting and weird fuel delivery had us stymied. WHAT THE DEVIL? Turned out it was a heavily corroded swag within the positive battery clamp (where the wire is soldered into the clamp). Neither the starter motor nor the nascent electronics in that '89 was getting good "12V". A lousy cable was all that was needed to straighten it out. Kira ps The new owner dynoed the engine at the flywheel-412HP on a small block "383" conversion.
 
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I don't think it's an original observation, but I've decided that motor mounts fail a lot more than they used to, because they are now designed to be more soft and compliant than older designs. On Kira's topic, a college friend's car had a bunch of starting/charging problems, and her Dad, usually a very handy guy, just couldn't figure it out. The first time I looked at it I gave each battery cable a good pull, and one cable pulled right out of the terminal. A quick trip to the auto parts store for a replacement terminal, and she was good to go.
 

SwampSurvivor

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Originally Posted By: HangFire
I don't think it's an original observation, but I've decided that motor mounts fail a lot more than they used to, because they are now designed to be more soft and compliant than older designs.
Yeah - had that happen on the Focus. But the Cherokee was designed in the 80s.
 
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Originally Posted By: Miller88
Originally Posted By: HangFire
I don't think it's an original observation, but I've decided that motor mounts fail a lot more than they used to, because they are now designed to be more soft and compliant than older designs.
Yeah - had that happen on the Focus. But the Cherokee was designed in the 80s.
I was thinking of the 60's motor mounts. They were pretty dense solid rubber.
 
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