Newly installed Supra 5 speed conversion issue

(Robbiedog) #1

Hello All, I’m an avid stalker but seldom poster and now in need of help. I have recently installed a rebuilt Supra 5 speed gearbox conversion in my 140 OTS which I’ve owned for 30 years, I have also changed clutch to diaphragm type from Borg and Beck.
Installation was fairly straightforward after having flywheel drilled to accept new clutch. However immediately on starting the car there was a bearing type whine with clutch out - this disappeared on depressing the clutch which appears to rule out release bearing, whine increases with engine speed. I suspected either faulty spigot bearing or input shaft bearing.
I discussed this with the supplier who has been very understanding and fair, they suggested I returned the box for examination. So onto the ramp and out with the box. Removed clutch also to access spigot bearing which, when installed had splines on to grip crank. These splines had worn indicating it had been turning in the crank although I had only done 100 or so miles.
Today I reinstalled the examined box which I am assured is perfect, together with new spigot bearing with splines. I installed this with locktite.
Started the car and I’ve STILL got the whine.
Any of you clever guys got an idea what is causing this?
Incidentally I changed from the original Moss box due to increased wear,noise and fed up with going backwards when I thought I was in first at the lights!

(Robin O'Connor) #2

I take it you did preload the spigot bearing with oil, I’m assuming here that its an oil lite type/phosbronze?

(Robbiedog) #3

Yes I did soak the bearing in oil, although there were no instructions to do so. I did wonder why I was doing this because the oil clearly cannot last forever and it is impossible to access when installed without removing the clutch! The inner bearing is sintered bronze and as I understand it is this part which should rotate with the gearbox spigot

(Roger King) #4

A genuine Oilite bush will hold oil within the structure of the material. It should come ready for use, but it’s always a good idea to give it 24hrs soaking in oil.

1 Like
(Robin O'Connor) #5

The other way is to hold a thumb over one end, fill with desired weight of oil and then press your other thumb over the oil and compress until the oil exudes from the pores of the bush.

(Peter Crespin) #6

SThere is no movement of the input shaft within the pilot bush unless the clutch is disengaged. At all other times the clutch ensures the shaft is stationary within the bush - which is why it is by far the least hard-worked or failure-prone bearing in the powertrain because the crank and gearbox input rotate at the same speed any time power is being transmitted to the wheels.

So a movement noise that goes away at the only time it could possibly exist cannot be a squealing bush and must be beyond that point when depress the clutch stops all motion in the gearbox. It is possible for a gearbox to pass static measurement and inspection and still make a noise when dynamically tested, as in being used in a car.

I’ve never examined the Supra box but it sounds like the metric or resized nose could be borderline too tight in the bush and causes it to spin in the crank (although the above still applies)

1 Like
(Roger King) #7

I think this could be related to the clutch release bearing. If the whine disappears when you depress the clutch, that would add up as it’s under pressure and working against the pressure plate. If it whines with the clutch out, and the noise changes with engine revs, it’s possible the release bearing is not setup correctly against the pressure plate fingers/diaphragm. I would check with the installation manual or supplier as to what the correct way to setup the release bearing is.
As an example: my '68 Mustang was built with a three-finger clutch cover plate to work with a Toploader gearbox. The correct adjustment for the release bearing is 1/8" clearance so the bearing doesn’t drag on the pressure plate. When I restored the car, I fitted a BW T5 5-speed gearbox. This is as used in a late model Mustang, so the parts all work together pretty well. The conversion switches to the later Mustang cable clutch - and requires the release bearing to lightly contact the diaphragm fingers, so it turns at engine speed. This is as advised by Ford but is frequently done incorrectly in this conversion.
I would get definitive advice on how your clutch release bearing should be adjusted for this conversion. If all else fails, consult a Supra manual, maybe.

(Robbiedog) #8

Many thanks for the replies and suggestions. I am away for a week now but plan to totally move the clutch adjustment threaded rod from one end of the spectrum to the other, run the engine with this in both positions which should either eliminate or commit the release bearing.

It’s interesting that when listening to the noise with a stethoscope it appears to emanate from the bellhousing area and then toward the flywheel end, I appreciate sound travels readily along a metal shaft which confuses the issue. Peter’s suggestion that the input shaft nose is machined marginally too large for the bearing makes a lot of sense but I’m not sure how I would ascertain this. I haven’t actually reverted to the supplier that the noise still exists - I would like to get all the ducks in a row first.
I have a bit of a France trip in the car planned soon with not a lot of time to take out the box again etc beforehand. May just have to run with it and have the discussion with supplier on my return. I still have to fit the transmission tunnel and carpets which will dull the whine on our drive - as will some French Burgundy!

(Roger King) #9

…but as Peter has said, the spigot bush is not causing the whine.

(Ewout Barents) #10

Hi, I had a similar mistery after installing the 5 speed supra box. Also a whining noise connected to the engine speed. But it turned out to be a slightly slackened timing chain. It is still a mistery to me why this happened during the gearbox swap.
But all is good now, no more strange noises and a wonderful 5 speed box which I like very much!