kentuckyKITT

iTrader: (4)

On my '82 Trans Am, I recently replaced my transmission mount and now have a pulsing vibration that increases or decreases with speed of the car. The car has a 350 Turbo with the B&M torque arm kit. This vibration started immediately after I replaced the mount. First of all, the only reason I replaced the mount is because I was under the car for something else and saw a half moon shape piece of rubber sticking out from the cross member. When I replaced the TH200 3 years ago, I used the same mount since it appeared to be ok and was nice and solid. It was also a factory mount. Obviously, it was time to replace it after seeing the rubber sticking out.

I replaced the mount with an identical new factory "made in korea" mount exactly like what was on it. I did notice that in order to get the new mount/crossmember back on, I had to jack up the transmission a bit higher, not much, maybe a 1/4" more. I was already concerned with this to begin with. After feeling the vibration during the test drive, I brought it back and checked everything to make sure I didn't miss anything and all appeared ok. Well after advice from someone else, I pulled the drive shaft and found the front u-joint had a little bit of drag, so after being told I might have a tight u-joint by raising the transmission, I had new u-joints put in the shaft and re-installed it. I still have the exact vibration. Then, I tried shimming the cross-member down a 1/4" inch to bring the transmission back down exactly where it was. I still have the vibration.

My rear view mirrors vibrate along with the entire car like I have a subwoofer dropping bass notes every 1 second or so and depending on what speed I'm going, if I coast (as in let off the accelerator), it goes away kind of. I've read threads on here about people having issues with poly mounts causing vibrations, but this one is stock, so I'm at a loss here.

sofakingdom

iTrader: (1)

The pinion gear in the rear end, should be exactly parallel to the crankshaft & trans shafts. This will result in the U-joints being turned at the same angle. If not the case, then in addition to rotating motion as it turns, the drive shaft will be forced to move front-to-rear a small amount. That's the source of the vibration.

If your 82 sags as bad in the rear as that 89 does (can't tell in the sig pic, but the 89 is at least 1½" too low in the back) then a set of rear springs, to bring it back to the right level, may well cure it, by restoring the whole rear end geometry to where it should be. Might even throw in a cure for wheel hop on the deal.

kentuckyKITT

iTrader: (4)

That's a horrible picture of my '89 sitting in my mole infested sagging, uneven yard.lol Although it does need new shocks, the '89 actually sits higher in the back than the front as does my '82. The '82 sits a little higher overall since it has relatively new springs and shocks (about 4 years old). The '89 will get this treatment eventually. Anyway, I'm not convinced I have a problem with the rear alignment and I'm leaning more toward the transmission angle since that is physically all that I altered. The strange thing is, this car never had a vibration, not even a quiver until I put a new mount in. I should have just left the old mount in there.lol I'm tempted to put the old one back and drive it and see if the vibration is still there.

Getting back to what I physically altered. This is how I changed the mount: I drove the car up on steel ramps and chalked rear wheels. With car in park, I placed my small 2 ton jack under trans pan with 2x4 for cushion and put light pressure on trans. I removed the transmission mount nut to cross-member, then removed all 4 bolts to the cross member and set cross member aside in the exact orientation from which I removed it. I then removed the old mount and compared it to the new one. Satisfied with "appearance," I installed the new mount, but then when I set the cross member back up against the mount, the cross member did not sit flat on the frame rails. I measured a 1/4" space give or take a 1/32" Baffled, I studied my jack which did not appear to move on me and it's only a few months old so I ruled out leak down of the jack. I then proceeded to jack up the transmission more so that the cross member sit flat on the frame rails.

I bolted the cross member back in, reinstalled the nut to mount and got it off the ramps. As soon as I started it and revved the engine, I knew something was different. It had the feeling of a header flange touching the frame vibration, subtle but there. I then drove it and noticed the pulsing vibration. This led me to bring it back and shim the cross member down 1/4 inch to essentially put it back where it was which had no effect. That led me to suspect u-joint from changing angle of trans the first time in 31 years which is why I had new ones pressed in and of course the front u-joint was getting bad, so that was a good idea anyway. Yet, I still have the same vibration.

Again, this car had no vibrations whatsoever until I changed the mount. It has to be the mount right?

sofakingdom

iTrader: (1)

No, not really.

A new mount couples whatever vibes are going on, more tightly to the chassis.

Try a protractor.

John in RI

iTrader: (167)

Before taking ANY OTHER STEPS; Remove the spacers and put the crossmember back to it's original position,.... tight against the frame rails.

I don't have any idea where your vibration is comming from, no one does. You could have a busted belt in your tire, a chipped tooth in the rear end or MANY other possible culprits. co-incidence is a real thing and it's possible that your vibration could be completely unrelated to your new tranny mount.

One thing is for sure; that crossmemebr needs to be re-installed properly !

kentuckyKITT

iTrader: (4)

Thanks for the response. Already ahead of you on the cross-member. That was just a "test." It's bolted in correctly and has been since the day I did the mount. I rarely rig anything permanently like that. It's definitely somehow related to the new transmission mount since I reinstalled the old mount this past weekend and the car idled and drove just like it did before without a single quiver of a vibration. It was absolutely perfect on the highway. It's now currently jacked up with no mount in it at all until I decide the next step.

I won't have much time to look at it this week with my schedule and it's not my primary car, so not important at the moment. I'll work with it some more this weekend, but I have to say I've owned 7 Trans Ams of varying years and this is the FIRST one to ever develop a vibration at the EXACT same time after simply changing a bad transmission mount and I've changed a few over the years. Coincidence maybe, but I doubt it.

sofakingdom

iTrader: (1)

You're falling for the classic "correlation vs causation" logical fallacy.

What you actually did by changing the mount, was to EXPOSE a vibe that previously had been isolated from you by your .... mount aka "isolator".

Few years ago, a friend of mine was going bald, and decided to shave his head. Lo and behold, there was this funky bump on it, that had been covered up by his hair.

OK now,


,



.




.

keep


going




.



Pop Quiz:


,



,


get



ready

,


.

Did shaving his head CAUSE the bump?


Did changing your trans mount CAUSE the vibe, either?

kentuckyKITT

iTrader: (4)

I guess you think you are clever. I guess a lot of people on here think you are clever. I half expected a Star Trek character image with some "clever" writing under it, or maybe a cat picture. I see right through you and frankly I don't need anymore commentary from you. I respectfully ask that you step out of here and go screw with some young kid who's never owned a thirdgen before. That seems to be your favorite thing to do. I've seen your posts on here over the years, tons of them and you don't amuse me at all. I love your latest on the 350 turbo leak. Do me a favor and don't offer me any help or respond to any more of my posts from this day forward. I'd rather my posts go unanswered than to read a single response from you. Thank you.

Obviously, I know I have a problem somewhere, but the hope was to find a good starting point here with some real actual thought out help. As usual, I will most likely figure it out on my own eventually. It was a nice pipe dream to think I might get a jumpstart on it with a response from someone else who might have developed a vibration immediately after installing a new factory mount and what their result was. I generally don't need tech help, but every once in awhile I do. I'm finding that this site is actually not a good place to post questions anymore.

sofakingdom

iTrader: (1)

Yeah I'm increasingly finding that people don't want REAL ANSWERS, they come here with some preconceived idea of what they're going to find, and then argue endlessly with anybody that tells them anything other than that. Gets real tiresome trying to help people like that. Not sure why I bother.

Good luck! When you figure how a trans mount can CAUSE a vibe, as opposed to TRANSMITTING AN EXISTING ONE, let us know.

TreeFiddy

Put the old mount back in. If the vibe goes away, its the 'hidden vibe ' coupling. If it stays, it's the 'co-incidental other event'.

jmd

iTrader: (4)

There are tonnes of threads on here about vibration.

Think about what really could be causing the problem when it didn't have the problem new. Something changed.

I'm going to go out on a limb here and say there may be a lot of third gens with sunken stock engine mounts. LOTS of F owners experience vibration with a taller trans. mount. A lowered engine would cause a similar change in engine/trans. angle. But, the stock mounts are pretty durable and the clamshell keeps them from easily breaking like other styles. So few people "need" to change them.

Ride height doesn't matter if the pinion angle and driveline angles are proper. But, it may put you at a point where adjustment via thicker or thinner trans. mounts won't get you to the right angles. And it also has impact on other suspension factors.

Pinion and output angles shouldn't be identical; the pinion should be a tiny bit lower. This helps u-joint bearings keep in motion instead of sticking in one place.

Good luck with your 82.

TPI-Formula350-

Is the new mount rubber or poly?

JamesC

iTrader: (5)

I assume the above means OE rubber. If not and the new mount is poly, you've probably found the problem.

JamesC

jwfirebird

iTrader: (2)

if the new mount is cheaper rubber, the torque arm on our cars puts upward pressure on the trans and subsequently the trans mount. if the cheap rubber is letting it flex more it will be higher when accelerating and may let something touch the body or just messing with the shaft angles. by the way i have been running poly mounts for about 10 yrs with no issue.

JamesC

iTrader: (5)

Unfortunately, many members do.

https://www.thirdgen.org/forums/tran...ison-pics.html

JamesC

jwfirebird

iTrader: (2)

I have a th400 and had a hurst conversion crossmember. now i made my own smaller crossmember to run lt's and dual exhaust, so it may not be the same issues as what the stock ones may have. but i put in the poly one when i converted to th-400

TTOP350

iTrader: (8)

OP, you said as soon as you reved the motor after you changed the trans mount something was different/had vibration, well that would be motor, converter or motor accessory issue because your DS wouldn't be spinning unless you had the rear in the air and trans in gear..
Do you have a clutch fan? (clutch fan going bad?)
Did the fan touch fan shroud when you jacked up the trans??
Did it move the shroud and now the fan is rubbing it?

kentuckyKITT

iTrader: (4)

Yes, that is correct. As soon as I started the engine, I felt something different. After it warmed up a bit and I revved it, I felt some vibration. My immediate thought was that the header collector flange was touching the frame again. I have these cheap stainless ebay headers which like to touch the frame on the passenger side. I remedied this back when I installed the engine. So, I thought since the transmission raised a bit, that also raises the engine and thus the header back onto the frame. However when I got back from the first test drive, I discovered the header was not touching and none of the exhaust is touching the body. So, that was ruled out. I'm real anxious to get back under it and investigate more.

kentuckyKITT

iTrader: (4)

I was considering a poly mount until I read all the threads on here. That alone prevented me from even trying that.

kentuckyKITT

iTrader: (4)

Definitely rubber. It looked identical to the one I took out, except the one I took out is missing a section of rubber. I re-used the stock mount from the TH200 when I put the TH350 in 3 years ago because it appeared ok at the time. I should have replaced it then, but there didn't seem to be a thing wrong with it.

I guess it's possible that the new mount has caused a "current" vibration to show up, but the intensity of this vibration leads me to think that I would feel this even with a worn out mount. My friend's dad who has worked on cars and raced cars for decades rode with me last night and he said it felt like I put a solid race mount in it. He's the one that helped me replace the TH350 and install the torque arm mount back then. He is baffled by it as well. He suggested trying another new mount since they are 10.00 and shockingly the parts stores stock them. I may do that I guess to at least rule that out.

kentuckyKITT

iTrader: (4)

Oh, no clutch fan, it's a flex fan and after noticing the transmission raised a bit, I opened the hood and check my distributor, dipstick, and of course the fan. Honestly, when I looked under the hood, it didn't appear that the engine moved at all from where it was, so I'm still not sure the transmission was raised. Maybe the jack did bleed down, I don't know.

kentuckyKITT

iTrader: (4)

There might be something there. I was planning on studying the B&M torque arm kit, bushings, and the torque arm this weekend.

jwfirebird

iTrader: (2)

that really woudnt apply if you feel it right when you start the engine.

kentuckyKITT

iTrader: (4)

Yea, that's why I said might. It is very subtle at idle, like the feeling of exhaust touching the floor pan/frame. Going down the highway, it's pulsating and intense which changes with speed of car. It's not constant at all as there is always pause between vibrations. I've never experienced anything like it in a thirdgen. I've had u-joints go on me and cause a continuous vibration, but nothing like this. I also discovered last Saturday I could make it subside by going a certain speed and then letting off the accelerator. It seemed to go away a few times completely, but as soon as hit the gas, back it came with a vengeance.

jwfirebird

iTrader: (2)

that does seem to be something with the torque arm either touching something it self or lifting up on the trans and making something touch there

kentuckyKITT

iTrader: (4)

Well, I solved the vibration completely. I went to the auto parts store and bought another rubber OE style transmission mount made by Anchor. It's only a 9.00 part and after about tearing my hair out looking for a vibration, I decided to try a different mount. It was in the exact same box except THIS TIME, the box and mount said Made in USA instead of Made in Korea. Guess what? It's perfect and I have zero vibration, I mean not a quiver. I took some comparison photos of both mounts and the boxes (the Made in Korea one) and the new one. I'll upload those photos tomorrow. I could tell right away as soon as I got the other one out the difference in quality and workmanship. The jest of it...the Korea mount is complete garbage made by complete idiots. That's the only conclusion I can come to.

rstoutZ28

ok this may be a dumb question but i have had the same extreme pulsing vibration in my car even after i changed the transmission from a 5 speed to a th350, whatever is causing the problem has caused 2 blown up 5 speeds and a cracked bell on the th350. anything?

rstoutZ28

ok this may be a dumb question but i have had the same extreme pulsing vibration in my car even after i changed the transmission from a 5 speed to a th350, whatever is causing the problem has caused 2 blown up 5 speeds and a cracked bell on the th350. anything?

jwfirebird

iTrader: (2)

i completely broke the bell on my first th400 (just a guess) im thinking it has something to do with the stress the torque arm can put on it. it was the first time i did a full power launch. i changed my mount setup and had the trans rebuilt with a different used case, nothing special but i have run it at the track with no further issue

rstoutZ28

but i still cant explain the horrible vibrations, its bad enough that if it was anything inturnal motor wise it would have blown up by now. i changed trannys, motor mounts, tranny mounts and the terrible vibration still continues. could it be a fouled out plug or anything silly that im looking over? its getting to the point that im sinking way too much money into the car

jwfirebird

iTrader: (2)

vibrations can be lots of places, tires is biggest one. could also be driveshaft, something in the engine,exhaust etc..

Cotymiller

Im new to this site but i just changed my transmission mount with another oem transmission mount. Nothing else and same mount.. Now when i hit the gas i feel a vibration. Its verry odd feeling and when i hit 65+ it shakes my whole undercarage.. I have a 96 camaro 3.8l with a 5 speed trans. I was wondering if you found out the problem or what should i do thanks

JamesC

iTrader: (5)

Hey, Coty,

Someone may respond to your question, but since this site is dedicated to 82-92 F-bodies, you'll have better luck in the future at the following site or one like it:

http://www.camaroz28.com

Best of luck,

JamesC