Q45 vibration... "new" transmission

[DrewQ45]

My Q is back on the road as of last week!!!

I was finally able to get a Japanese import transmission from an importer here in Atlanta. I ended up suffering some monetary losses though as the first transmission I picked was bad (will post on separate topic)… I ended up buying from another importer.

transmission cooler and brand new radiator installed…. It shifts nice and crisp but I noticed an issue. I now feel a vibration in the 30-35 mph range. This is not tire/front end related and I feel it in the seat of my pants. Seems harmonic in nature…. I’m pretty sure it’s drive-shaft related and some search of posts here confirmed it. Prior to this, I’ve never had a single vibe in the car so I’m reluctant to thing this is a bad drive shaft all of a sudden. Rather, I believe this to be the way the drive shaft was hooked up to the rubber gizmo that couples it to the rear of the transmission. Does anyone know if there is an optimal way to line up these things? Or maybe my mechanic may have changed something I’m not aware of? Maybe U-joint??? It's nothing I can't live with, but I’m taking it back to him during the week.

I now have two extra rubber gizmos…(not sure what it’s called)… was told by mechanic that they are very pricey items. Incidentally, the new trans came with a mount and cross-member already attached. The mechanic opted to use it instead of the mount I had on the car which was only a year old (ease of install?). Both mounts look good however, no cracks in the rubber. The rubber exhaust hangers are the ones that were already on the car and don’t seem to be too bad.

I’m sure this problem can be resolved (not sure if it will be easy though). The vibration is not bad and may go unnoticed by others, but it’s bothering me. I also wonder if there are vibes that I cannot feel in the higher ranges caused by this.

Final note… I’m running with the original 90’ TCU, but I’m going to reinstall the 93’ so I can start in 1st. On my old transmission, it was a rough shift under WOT. Hope it’s better with the new transmission.

…Drew…

[Q451990]

The rubber discs should never be separated according to the FSM. The shaft should have been completely removed during the swap. That could be your issue - or it could be that the "new" trans. mount is collapsed more than the old one. I would replace it. Even if the rubber isn't cracked - they will collapse and let the transmission sit directly on the crossmember.

Might be worth replacing the exhaust hangers too - just to eliminate all of the "cheap" stuff before you replace the driveshaft.

Did you have this done at T3?

Heath

[elwesso]

thats what i was thinking too... I bet you didnt replace hte transmission mount and i bet thats whats causing your issues...

There is an optimal way to orient the driveshaft on the differential, all marked with lines.

[DrewQ45]

The rubber discs should never be separated according to the FSM. The shaft should have been completely removed during the swap. That could be your issue - or it could be that the "new" trans. mount is collapsed more than the old one. I would replace it. Even if the rubber isn't cracked - they will collapse and let the transmission sit directly on the crossmember.

Might be worth replacing the exhaust hangers too - just to eliminate all of the "cheap" stuff before you replace the driveshaft.

Did you have this done at T3?

Heath

Heath[/QUOTE]

Heath, ... I think you hit the nail right on the head... and no, this wasn't done at T3.

When the used transmissions are removed in Japan, they cut right through the propeller shaft with a torch leaving the rubber disk and a few inches of the shaft at the end of the transmission. I saw about 4 trannys and this was how they all were shipped.

He (my mechanic) seems to have loosened the bolts, removed the cut portion of propeller shaft from the rubber disc, then attach the car's shaft to it. The propeller shaft along with the rubber coupling should have been removed all in piece...the shaft should have never been separated from the rubber. I don't think he reliazed how delicately balanced this thing is. It's all water under the bridge now... I'm going to bring back the two extra rubber couplings to him and see if he can figure this out. I'll also have him change the mount and maybe even the exhaust hangers if I can get a set soon. Thx

[Q45tech]

Also consider that the transmission [itself] has a rear main rubber seal which should always be replaced.

[elwesso]

Thats your problem. IF you disassemble the rubber discs like that, they are probably destroyed and the shaft will probably never be as it should again

[RobertsnewQ]

Thats your problem. IF you disassemble the rubber discs like that, they are probably destroyed and the shaft will probably never be as it should again

Yep - You have to keep Guibos (the name for those rubber couplings) together at all times or they go out of round/balance.

[DrewQ45]

Yep - You have to keep Guibos (the name for those rubber couplings) together at all times or they go out of round/balance.

Thanks for the education folks. I have one Guibos left that has not been pulled apart, unfortunately, it's from one of the used trannys so it has a cut section of propeller shaft attached to it. This means that I will have to remove the bolts on it. I'm going to find a way to immoblize the discs so they won't shift ...maybe I'll wire them together. I'll put back the bolts in the same places, torque them all the same torque....(not sure what that will be just yet). I don't have much of a choice right now other than getting another shaft. Like I said before, the vibration is really not bad and can be lived with, however, I liked the way my car was before...vibe free.

[elwesso]

Dont live with a vibration..... I did that and RUINED the tailshaft of my transmission, still leaks a little.....

[RobertsnewQ]

Use a big hose clamp around the outside to keep it together.