craigw1

Hi all

some quick background : S5 tii and gearbox into a first gen. used the rb front bracket and oil pan to mount motor so that gearbox in stock position. Did the tail piece mod and cut the selector. Also, fabricated a gearbox mount bracket between gearbox and cross member. Here i used a hard piece of rubber sandwiched between two metal pieces. <see pic>




the problem : persistant vibration, felt through the gear lever and also if i rest my left foot on the foot rest. The vibration is so bad that like driving for 10mins and i get out then my foot/hand is like almost numb, pins-and-needles like sensation.

methinks it must be gearbox related.

was thinking of doing the following

1) drain oil and refill
2) fabricate new mounting bracket with harder piece of rubber.
3) replace rubber on the cross member bolts

any other ideas ?

ps. can't be the driveshaft as i had it made up to fit so was balanced....unless i must have it balanced again ???

IanS

iTrader: (4)

Sounds to me like the rubber needs to be a bit softer for your mount. I put solid motor mounts on my car and instantly noticed a considerable amount of vibration in the floor and the gas pedal. I would assume that your trans mount is simply transferring vibration to the floor and shifter. I wouldnt go harder, but SOFTER at first.

craigw1

aha !

good point...you might be right.

anybody else comment ? had similar problem ?

Rogue_Wulff

When I bought my car, it had a vibration similar to this. The trans has a 2ng gen N/A tailshaft housing, so the PO used a rubber shock washer, and run 1 bolt thru the crossmember, into the trans. I got a used 1st gen crossmember, and a 2nd gen with mounts. A little cutting and welding netted me a custom unit for a 2nd trans, in a 1st gen.
Vibration suddenly went away when I installed the new mounting device.

craigw1

have u got a pic of this 'mounting device' ?

or can you describe in a little more detail please, thanks

Rogue_Wulff

No pics, sorry. My camera died, so I can't even get any "after" pics.
It's just a 1st gen crossmember "Modified" to accept the second gen cradle-style mount. Made my own collar for the center stud's rubber bushing, and added a slot on one side for the side mounting pad (how lucky can ya get?), and a bracket on the other side, for the other side mounting pad.
The 2nd gen N/A trans has the mounting hole in the same area (front to back) as the 1st gen, but the holes are closer. I probably could have just re-drilled the stock 1st gen mount, so it would bolt to the trans, but the 2 crossmembers, and 2nd gen mounts were given to me. Free + a couple hours of fabrication work was more my style, compared to $50 for a new trans mount, plus a few minutes of fabrication.
Of course, It was a little "tricky" to get all the bolts and nuts installed, and tighened down. I suspect the 2nd gen has a little more room at the crossmember mounting location.

craigw1

seems like there is manyways to skin this cat. i've seen some guys even using spacers between the cross member mounts.

I guess the point is that the box is transmitting loads of vibration, and one just has to try and 'damp' it as best one can.

if you look at my pic, what you can't see is that there are two bolts going right thru from the cross member, thru my tranny mount and into the tranny.
its amazing that all this vibration is actually being transmitted thru these two bolts, thru the cross member, and thru the cross member mounts back into the body...and i'm feeling it with my left foot !

i think i'll start off first by putting some rubber between the cross member bolts and the body. Then i'm also going to put a piece of rubber before i push the bolts thru the cross member into the gearbox. I'm also going to loosen those bolts a bit so not as to have too much tension on the rubber. Finally, i'm going to have a look at the std piece and see if i can incorporate somehow.

Rogue_Wulff

If all else fails, make an adapter plate to bolt the stock 1st gen mount to the T2 trans. If you don't get too close to the rubber, you can even weld the plate to the stock mount.
The pic appears to show the T2 mount is slightly further back from the 1st gen location.

steve84GS TII

Have you tried eyeing down the length of the driveline to be sure its straight and true from the tranny to the rearend?
I mean the entire drivetrain alignment,not just the driveshaft itself....
The vibration could be the u-joints having to work to correct a mis-alignment between the tranny and rearend.Also,if you have zerks on them,did you grease up the U-joints before install?Most driveline shops do not grease the joints prior to giving you the unit.Dry joints will fail very quickly and cause vibrations....

craigw1

geez...seems like it could be more complicated than just the gearbox mount.

how can i check the alignment of the driveline ? Do the shops have some sort of special tool to do this ?

craigw1

i think i need to make up a mount like this. at no point on this mount is there metal to metal contact. The bracket mounts to the gearbox, then is bonded to rubber, which is then bonded to another bracket which mates to the cross member.



in my case i sandwiched the rubber between the gearbox and cross member but there is still metal to metal contact because there are two bolts going from the cross member straight thru the rubber and into the box.

Rogue_Wulff

That looks like a stock 1st gen mount, modified to fit the trans. Looks like they cut the original "Ears" off, and welded new ones on. Only special step to doing that, is making sure the rubber doesn't get damaged from the heat.

The way you done it, any vibrations fron the engine, trans, or driveline (and there will always be some) go directly into body. The rubber you put in, doesn't absorb them, and might as well not be there.

Kentetsu

Make sure that your exhaust system is not in direct contact with any part of the chassis. Does it vibrate in nuetral, or only when driving?

steve84GS TII

Thats similar to what I did.
Just cut the excess off the stock 1G tranny mount,then re-drilled the holes and bolted it straight to the TII tranny.Because the 1G mount pushed the tranny up a lot more than the FC mount,I had to space the crossmember back down an inch to maintain tunnel clearance and driveline angle.
Did that with a couple cylindrical spacers on the crossmember mount points(actually used a couple 3/8 drive sockets for a short time).Those got everything back into alignment and also,they dont delete the rubber isolators on each side of the FB tranny crossmember.....

Drivetrain alignment would be obvious to the eye.You should see a straight line from the engine/tranny/driveline/diff input.If the tail off the tranny is skewed to one side and the driveline has to angle the other way to meet up with the differential,there is going to be some vibration.Its a simple matter of drivetrain component placement, which is determined by motor mounts,tranny mount and rearend suspension pickups(trailing arms/Watts links). Bent,sagging,torn or non-standard mounts/parts will change the factory placement of the drivetrain components.

GavinJuice

if i remember right you always want some sort of a pitch in your driveshaft to prevent excess wear on the u-joints? something along those lines? i think i read that in a post on here before

craigw1

Still have a problem.....but i have made progress

today I took out my home made, useless bracket.

I then screwed off the two stock rubber pieces from the t2 mount and screwed it into the bos and into the cross member. It fitted perfectly and the width was the same width as my home made bracket

out on the road and lo and behold, the vibration at the foot pedal is GONE !

BUT

instead of having a vibration thru the gearlever, the whole gearlever is now shaking...even so much as to loosen the rubber boot surround !

well, i guess what is happening is that as there is no metal to metal contact, the in car virbation is now gone ie the vibration is all being 'damped' by the two rubber bushings.

however, the gearbox is now more flexible than before, so is vibrating even more, hence the whole lever vibrating

I guess I have one last option...and that is to bastardise the first gen mount in my earlier picture. Still no metal to metal contact so there should be no in car vibration. however, the rubber is bonded to the sides, and so is less flexible than my current setup

well, at least today was a step in the right direction as i removed the in car vibration, so i'm at least a little pleased

craigw1

ok, another 2 hours back under the car today. slotted the original first gen mount and bolted it to the tii gearbox. so far so good. tried to fir the cross member....damn...the two bolts are now closer together. drilled new hole in cross member, back under car. Hey hey it fits first time ! ok, now to bolt in the cross member...made 2 hard rubber spacers, and hey presto, it bolted back into position. gearbox should be in the same location, as my bos mount is now taller, but offset by the spacers on the x-member.

out on the open road....little vibration at the foot rest....but yesterdays lever boot vibration is much more toned down.

well, i've tried all three solutions now. this latest one is so far the best outcome. there is vibration, but not as much as when i had no rubber 'damping'

sure, yesterday's solution had less vibration at the foot pedal...but then the lever went wild....it was just too flexible.

so there you have it guys. If you want to mount a tii box in a first gen, go with the first gen mount, and put spacers between cross member and the body