Is the angle of gearbox mounts isolators critical?

[Momus]

I did 13B rotary turbo into a 116 transaxle type Alfetta GTV and had some vibration issues I diagnosed as being related to the engine speed driveshaft which was mounted to a carrier on the crank. The driveshaft was very similar to yours.
I'm a little hazy now on the details but I spigoted the tailshaft to the crank via an extension on the tailshaft's BMW/V6 Alfa Guibo flange using a teflon lined spherical bearing housed in the crank adaptor.
I worked out where the thing wanted to naturally pivot to allow for engine mount flex. This worked out a lot better compared to the standard locator.

[BMWTurbo]

I did 13B rotary turbo into a 116 transaxle type Alfetta GTV and had some vibration issues I diagnosed as being related to the engine speed driveshaft which was mounted to a carrier on the crank. The driveshaft was very similar to yours.
I'm a little hazy now on the details but I spigoted the tailshaft to the crank via an extension on the tailshaft's BMW/V6 Alfa Guibo flange using a teflon lined spherical bearing housed in the crank adaptor.
I worked out where the thing wanted to naturally pivot to allow for engine mount flex. This worked out a lot better compared to the standard locator.

Ta mate. I'm having a hard time visualising what you are describing there. Toyota have a stub on the gearbox, that extends out and in to a bush in the centre of the taishaft side of the spider. The rubber coupling float between this 3-holes to each side.

I modifed the mount and did some more diagnstics. It's not engine or RPM related, it only happens when the TS is connected. I slide the TS back and let it spin on the above mentioned and every gear all through the RPM range was smooth, no harmonics.

Connect the TS back up and they are back. I clocked the guibo one hole on the gearbox side also for 'justin' - no difference. no noticeable increase in vibration by connecting the second half shaft either, so pretty sure it's not related to them now.

Checked the TS again and front section runs true, I can't see any movement, the rear section however has some run out in it. In Jan when HS did the shaft they assured me it was all perfect. I specifically asked if they should be replacing the rear tube and they said nah it's fine. I'm not convinced it was perfect to begin with now. Although better than when I took it in I've been looking in other area's but perhaps I shouldn't trust so much, or I've managed to bend it since fitting.

I haven't driven the car but suspect it will be a bit better than previously as I also replaced a bent half shaft, but am not at all happy that the TS 'appears' to have run out in the rear section now.

[Momus]

Ta mate. I'm having a hard time visualising what you are describing there. Toyota have a stub on the gearbox, that extends out and in to a bush in the centre of the taishaft side of the spider. The rubber coupling float between this 3-holes to each side. Pretty much the same thing as you see locating Guibos except a bit more accurateI modifed the mount and did some more diagnstics. It's not engine or RPM related, it only happens when the TS is connected. I slide the TS back and let it spin on the above mentioned and every gear all through the RPM range was smooth, no harmonics.

Connect the TS back up and they are back. I clocked the guibo one hole on the gearbox side also for 'justin' - no difference. no noticeable increase in vibration by connecting the second half shaft either, so pretty sure it's not related to them now.

Checked the TS again and front section runs true, I can't see any movement, the rear section however has some run out in it. In Jan when HS did the shaft they assured me it was all perfect. I specifically asked if they should be replacing the rear tube and they said nah it's fine. I'm not convinced it was perfect to begin with now. Although better than when I took it in I've been looking in other area's but perhaps I shouldn't trust so much, or I've managed to bend it since fitting.

I haven't driven the car but suspect it will be a bit better than previously as I also replaced a bent half shaft, but am not at all happy that the TS 'appears' to have run out in the rear section now.

You won't necessarily see any out of balance as runout and you could have balanced run out...and I doubt you have bent it.

However, by the reasonably gross symptoms the problem should now be easy enough to pinpoint. My hunch would be runout and out of balance at opposite ends of at least one section, by your description probably the rear now, causing some sort of rocking couple ....

I have to say the best of the complicated custom tailshaft jobs I see are done by machinists in engineering workshops rather than tailshaft specialists. Machinists are usually more patient and better equipped and if the job is being made from a mix of parts, tend to have experience in getting things running properly true, and round.

That said it could come at a price. 15 or 20 years ago Harrop used to get over $3000 for a race 2 piece shaft with similar duty rated parts to yours.

[Cameron_Datto]

check the large cylindrical bushes on the rear cross member that mount to the body . if they are ok there should be about a 6 mm(aprox ) air gap between the large retaining washer on the bottom , if the there is no air gap between the washer , the bush is buggered , this will cause the diff to change its pinion angle .

also make sure you have a correct centre bearing for that model . if have seen people spend alot of money chasing a vibration only to find out the wrong centre bearing was fitted .

Front what iam told some manufactures put there TS unis slightly out of phase to counter Act vibrations in the drive live

[BMWTurbo]

You won't necessarily see any out of balance as runout and you could have balanced run out...and I doubt you have bent it.

However, by the reasonably gross symptoms the problem should now be easy enough to pinpoint. My hunch would be runout and out of balance at opposite ends of at least one section, by your description probably the rear now, causing some sort of rocking couple ....

I have to say the best of the complicated custom tailshaft jobs I see are done by machinists in engineering workshops rather than tailshaft specialists. Machinists are usually more patient and better equipped and if the job is being made from a mix of parts, tend to have experience in getting things running properly true, and round.

That said it could come at a price. 15 or 20 years ago Harrop used to get over $3000 for a race 2 piece shaft with similar duty rated parts to yours.

I'm tempted to grab another std one and get a second spider fitted to it. This TS has cost me probably close to $1750 total now, from the original 'new' build rechecking balancing, and the last time with spicers. On it's second rear CV and second centre bearing. I will talk to HS tomorrow about it and see what they want to do. I hear what you are saying, but cannot justify $3k on a new shaft.

Found a photo of the shaft before sending to HS in Jan.

check the large cylindrical bushes on the rear cross member that mount to the body . if they are ok there should be about a 6 mm(aprox ) air gap between the large retaining washer on the bottom , if the there is no air gap between the washer , the bush is buggered , this will cause the diff to change its pinion angle .

also make sure you have a correct centre bearing for that model . if have seen people spend alot of money chasing a vibration only to find out the wrong centre bearing was fitted .

Front what iam told some manufactures put there TS unis slightly out of phase to counter Act vibrations in the drive live

I replaced the rear crossmember cans with new HD Meyle ones earlier in the year. I also did the 3-off diff rubbers at the same time. They are fine and have the clearance as you mention. They did ride up the first eek, but since reseating haven't moved.




I know that phasing on uni's is a big thing, I haven't been able to find any information re phasing of CV's/Guido's relative to CV's though. I would have checked this but don't know what I'm looking for. CV's by nature shouldn't mater and the fact that I have the guibo pretty much dead in line (ignoring GB mont flex). Many factory TS's run a single uni so it's not out of the ordinary either.

Centre bearing seemed to be the same and had the right number on the box. HS fitted this for me so I didn't compare side by side though.

[BMWTurbo]

Went and saw the guys at HS and suggested they have a look at it to ensure I wasn't seeing shit that wasn't there.

One of the fella's inspected it and commented it has about 10-15 thou run out in the rear on the CV stub. I'm rather pissed off that this wasn't fixed or didn't stay fixed from Jan. In short they'll warranty the balance and look after me if it needs a retube (which I'm pretty certain it will, as clearly whatever they are doing isn't lasting). Which means I get to remove the TS again.... joy....

[BMWTurbo]

After some hiccups... The TS has a new rear tube and is fitted and when the engine/box/TS/diff only are spun up, there is some vibrations through 80kph odd, but nothing too excessive, so I'm comfortable the TS is okay for the moment. Vibrations with the HS's and wheels connected were evident at >50kph all the way and fairly horendous. Even tried dropping the engine mounts and replacing them with wood blocks and noticed no real difference.

This leaves half shafts, which I have had some issues with in the past. I've replaced both bent BMW shafts with some larger A/M shaft only (straight), but it seems they are still vibrating. I stripped, cleaned and reassembled them a while back, noting the direction of the cages, outer and inner, but not the balls nor the clocking of the inner v's outer. I assembled the shafts the CV's are facing the right directon and indexed in phase with each other. (ie small to large). So I may have fucked them up somehow... Shafts seem to run true as do the CV's on the diff and TA. Wheels feel free to turn with no shats connected and I can't feel any slop in the wheel bearings.

If I can't source some used shaftsw for a fair price... BMW are conveniently the same inner spline inner width outer diameter, same PCD and stud size as PORSCHE 930 CV's. The 930's are 40mm wide whereas BMW are only 32mm, but this is only the outer and longer bolts will sort that.

For about $400 I can get 4-off brand new Meyle CV's, 4-off GKN BMW boots and backing plates and 50-off m10 x 60mm GR12.8 SHCS to suit. Bunging that on to a spare set of large A/M shafts, I'd basically have a brand new set of half shafts.

I'm cautious about using BMW A/M/replacement stuff as I went through two sets that lasted a few months at most before turning to puss. They were made in China and shit, only having 19mm balls, not 22mm like the BMW/PORSCHE.

The other option would be a CV reco'r. I think there is one at Slacks Creek, but not convinced this is a better way than replacing with new Meyle CV's.

[styler]

Not sure if relevant but was interesting none the less.. had a tailshaft made up and found out the unis's will cause vibrations
if not equally off centre through the range of motion, so the gearbox and diff must be mounted square independently but between
the two they can be offset as it would result in an equal amount of offset between the two as they move, as sometimes
collapsed mounts and diff conversions with different pinion angles cause this change of angle on either side that causes shit.

[BMWTurbo]

Not sure if relevant but was interesting none the less.. had a tailshaft made up and found out the unis's will cause vibrations
if not equally off centre through the range of motion, so the gearbox and diff must be mounted square independently but between
the two they can be offset as it would result in an equal amount of offset between the two as they move, as sometimes
collapsed mounts and diff conversions with different pinion angles cause this change of angle on either side that causes shit.

Thanks for the suggestion mate. I only have one uni in the TS so the angle has to bbe the same in and out as far as I can tell.

I have changed all mounts within the last 2-years.

I got hold of a pair of VGC half shafts today and fitted them tonight, they run as straight as a die when in the car and the vibration is still evident. I did test 'again' with the engine/gearbox TS and diff only connected and paid a lot more attention this time and there was vibration from about 60kph upwards. I may have overlooked this previously as it was substantially less then with the half shafts connected.

One thing I can play with is the centre bearing height, but this will affect the alignment of the gearbox to TS as I don't particulalry want to raise the engine mounts and can't lower them.

[styler]

Not somehow diff related at all? Also as far as I understand it with the alignment... as long as each point is in the parallel plane
of each other point you shouldn't have vibration but if it isn't then you will, if you get what I mean. Like if you put a rod perpendicular
on each end and perpendicular through every mid point those rods even although offset and distanced away from each other should still
be parallel to each other. With engine, gearbox and diff conversions and fabricated mounts those rods as such may not be parallel anymore...
just saying Else you got a bum setup, like some cars just seem to get an inherent vibration from the setup that's used and yeah harmonics
and shit just not getting on too well.

[BMWTurbo]

Not somehow diff related at all? Also as far as I understand it with the alignment... as long as each point is in the parallel plane
of each other point you shouldn't have vibration but if it isn't then you will, if you get what I mean. Like if you put a rod perpendicular
on each end and perpendicular through every mid point those rods even although offset and distanced away from each other should still
be parallel to each other. With engine, gearbox and diff conversions and fabricated mounts those rods as such may not be parallel anymore...
just saying Else you got a bum setup, like some cars just seem to get an inherent vibration from the setup that's used and yeah harmonics
and shit just not getting on too well.

I spoke to the chaps that rebuilt the diff for me the other day and they are confident it isn't diff related. It's is a fast vibration so not half shaft related.

You don't want a tailshaft to be dead axial if it has a uni joint in it as the uni joint will wear out much much faster if it's dead straight then if it has a couple of degrees inclusive angle.

I have tried moving the centre bearing forward for 4/5mm pre-load and no change. I'll move it back and try that, then I'll try a lower/higher gearbox mount and if I have no joy I will drop it back out and take a reference ( similar to what you describe) so the TS can be set up as it is in the vehicle on the balancer.

Balancers run the TS fairly true and the CV's etc in there 'nuetral' state, which isnt how they are in reality.

[Gammaboy]

I did 13B rotary turbo into a 116 transaxle type Alfetta GTV and had some vibration issues I diagnosed as being related to the engine speed driveshaft which was mounted to a carrier on the crank. The driveshaft was very similar to yours.
I'm a little hazy now on the details but I spigoted the tailshaft to the crank via an extension on the tailshaft's BMW/V6 Alfa Guibo flange using a teflon lined spherical bearing housed in the crank adaptor.
I worked out where the thing wanted to naturally pivot to allow for engine mount flex. This worked out a lot better compared to the standard locator.

That would have been an interesting thing... better than the holden powered 2600 sprint you put together.

[Momus]

Rotary was goodish- owner was impatient, underfunded and insisted on persisting with an LPG turbo.
I was never able to put an aluminium flywheel and the small multi plate clutch in it to see how much this picked things up.

Old Alfas.
Saw a very nice Montreal cruising down Sydney Rd the other day.

[BMWTurbo]

Could only confirm vertical'ish alignment due to exhaust, but with things they way they were there was 0.26 deg angle through the Uni. I spaced the centre bearing down 5.8mm and have ended up with 1.64 deg odd inclusive and will try that.

I have no idea how much horizontal angle is in the uni but I am pretty certain it is some, so the above may not do a pinch of shit. I'll confirm horizontal alignment when I drop the exhaust over the weekend.

I know this can be resolved as it has been much better previously.

[BMWTurbo]

97% resolved with a third balance. Haven't noticed any vibrations when driving, but went through a harmonic around 60kph and a second about 120kph smooth below and in between...

*touch wood*

[Uncle Arthur]

Three balances to get it right, geez. Anyway, persistence pays off

[BMWTurbo]

Three balances to get it right, geez. Anyway, persistence pays off

Only cost me a set of half shafts, new gearbox mount, probably 30 hours of my labour, inconvenince of not having the car during works and the initial cost of the front shaft replacement to get there :P

Oh yeah... and over $2k for a new set of wheels/tyres.

I know have the most comprehensive set of measurements/alignments and photo's for a BMW TS in the world :P

[BMWTurbo]

No Dice... It's back again, lasted one maybe two trips before re-surfacing.

Been vibrating 63-85/90kph and when marked this afternoon with a white pen when spinning clearly shows run out again.

NFI why it keeps running out. Maybe the tube is twisting or something?



Have to drop it out and back again.....

[bahaimus]

What a cunt.

[tim510]

convert it to FWD. that should fix it.

[Greg Rust]

Has the gearbox extension housing bush been talked about yet?

[BMWTurbo]

What a cunt.

It seems building a straight/balanced TS for a BMW is about the same complexity as building a rocketshuttle... Must be the leventy million HP I have realigning the gravitational pull of the earth around the TS distorting the space-time continuum...

convert it to FWD. that should fix it.

Suspect this would be simpler/cheaper than getting a smooth/straight TS in the car.

I believe the plan is to pull the rear section apart, recheck each component and then build a new rear section with Chomoly tube this time.

[BMWTurbo]

Has the gearbox extension housing bush been talked about yet?

I checked for missalignment and runout in the gearbox output spider with a feeler gauge and reference and didn't see more than 0.1mm variation between them. I can't notice any slop in teh output flange on the box when grabbing and trying to shake it etc.

I also removed the spider and inspected and retorqued the nut that holds it on to the shaft.

The run out seems to move around which is the confusing thing. Old shaft is was on the RF (behind centre bearing) and FF (gearbox spider end), after a balance/straighten/replace front tube (chromoly) it showed on the RR section (ie diff end), second attempt after a rear retube with thick walled steel, I'm not certain (removed and dropped back) and after the third attempt it's now showing on the RF section.

Currently the RF is what is in the VDO (IT must be in the tube as the centre bearing is mounted on the rear shaft. The front tube runs pretty true Front and Rear, but rear tube runs out front, but runs true on the rear.

Shaft felt okay the first drive after install, but vibration came back a day or so later. I can only assume I'm twisting the tube or something along those lines.

[Uncle Arthur]

Mofo, sounds like there is some sort of basic alignment problem. Tried changing the center bearing height?

[BMWTurbo]

Mofo, sounds like there is some sort of basic alignment problem. Tried changing the center bearing height?

I've done everything I can think of or had suggested :-
- The gearbox output is in line and the same location as the BMW gearbox (I have raised it lowered it, moved it left and right and everything in between, currently set as axial to centre bearing in vertical and horizotal plane)
- Centre bearing I have raised it slightly (~ 1-2mm, can't easily do) and moved it foward and backward (preload in either direction) and also lowerd it up to 5mm
- Brand new rubbers in the rear end, so set exactly as per factory in relation to diff location, height and pinion angle
- Fairly new engine mounts (did it with monuts replaced with blocks of pine) and brand new gearbox mounts as per start of thread
- Does it with or without wheels
- Does it with half shaft to wheel removed, so TS-diff only
- No movement of tears etc in body work/mounts
- Inclusive angle it between 1.5-2 degrees between front and rear TS sections (which is perfect from all the literature I can find for uni's)

[Momus]

Looks like average workmanship with the size of the weld bead- TIG would be nice.

I think the shop are doing less than they say and you may have a shaft with a slightly cocked end or out of square tube that has perhaps been heat straightened between centers in a lathe and then remembered where it wanted to be.

[BMWTurbo]

Looks like average workmanship with the size of the weld bead- TIG would be nice.

I think the shop are doing less than they say and you may have a shaft with a slightly cocked end or out of square tube that has perhaps been heat straightened between centers in a lathe and then remembered where it wanted to be.

You are no doubt correct. I had thought about the tube returning back to it's initial shape when being stressed. Hopefully Chromoly won't exhibit the same properties. The front section has been true since it was changed to chromoly previously.

They also mentioned about running it on another balancer. They can't 'load' the shafts however, so if might be true to start with and balance like a champ, but then go back to it's original state. I think it was the second incarnation I saw on the balancer and it was smooth all through the RPM range.

[Momus]

Not that I make many but I won't use anything other than 4130N or the new equivalent; preferably US manufactured, for tailshafts.

[Gammaboy]

Try driveline services - I don't think I've heard any complaints about them.

[BMWTurbo]

Try driveline services - I don't think I've heard any complaints about them.

Bad taste left in my mouth when I went to see them originally, just to get the BMW shaft shortened and the Toyota spider fitted and they said it was too hard for them to do. Mentioned they'd done a BMW shaft previously and coulldn't balance it fter 8 hours on the machine.

After they told me that I haven't bothered contacting them again.