Transmission noise

Hello Christophe,
You could have the ID of the First Motion Shaft and the OD of the Main Shaft machined, sleeved with hardened sleeves (only the sleeve for the Main Shaft needs to be hard) then machined back to original dimensions. I can measure the parts and supply sizes if you go that way.

Denis Welch Motor Sports make replacement Main Shafts.

You don’t remove the Rear Bearing circlip to remove the Bearing and at the same time, dismount the Main Shaft. I believe it states to remove it in the Haynes Manual that your using, but that is for the Moss Box. As I stated in an earlier Post, that book refers more to the Moss Box; the procedure is quite different with the later Gearbox. Get yourself a manual that discusses the later Gearbox specifically.

Regards,

Bill

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Preformatted textChristophe I have the mainshaft ground and a sleeve pressed on. The sleeve used is the companion inner sleeve for the needle roller , although some years ago
I obtained some thinwall sleeves that I prefer to use. Photo shows a mainshaft
sleeved 2 / 3 months ago.
You do not need to remove the circlip on the rear roller bearing. (photo)
Is the outer cage of the needle roller still in the first motion shaft, normally the case.
To remove the mainshaft I use a rudimentary pusher / puller, otherwise a
hide mallet.
I am in 49 close to Bauge` / La Fleche.

The main shaft can machined for to accept the sleeve, and make sure you use a full complement needle roller bearing, not the one shown, to get a bearing with greater load capacity, and therefore reduce to the chance of this happening again

It`s Christtophe that needs the reply Norman ! but the more the merrier.
By full complement do you mean the needle roller @ 1 inch rather than point 75"
BTW do you use a thick wall or thin wall sleeve?
Peter B.

The only reason the full complement bearing is better, and only marginally so, in this application, is that the differential Revs the Main Shaft Journal is running in the bearing are quite slow, Zero in Top Gear, fastest in First Gear. The only time considerable revs would be involved is in Neutral, clutch engaged and the engine at max revs. In a high revving application a caged needle roller bearing is a better choice than a full complement bearing. A full complement bearing is more adversely affected by poor lubrication than a guided cage type. Accordingly, you would need to ensure that the oil pump of the gearbox is working well, something that is often not with the gearbox being discussed.

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Given the dimensions @1inch for the main shaft spigot and 1. 250” for the first motion shaft counterbore, what is the alternative to a needle roller?
Or !! are you blokes suggesting a bush rather than a bearing?
Peter B. If

Whilst there is only 7% difference in the Dynamic Load capacity, the Static Load capacity is 20% better (11600lbs. compared to 9640lbs.). Much better able to handle the high shock load experienced with a “RACE” style (abuse) start.
Even behind a V12, the speed differential of the first motion and main shaft is less than 5000rpm.
I have been using the “Full Complement” bearing for both race and road applications behind both 600+HP V12’s and 350HP 6 cyl. 7500rpm engines for the last 40+ years without any failures.

Its rather irrelevant whether the gearbox is behind a V12, or XK 6 cylinder engine with regards to the bearing RPM, unless the engine is some super high revving engine. First gear is where the bearing RPM will be the highest, other than in Neutral. In first gear, for the differential RPM of the bearing to be 5K, the first motion shaft (engine revs) would have to be a revving at 14,665 RPM.

Full-complement bearings may publish higher load ratings, but these are mathematical values that assume ideal operating conditions. Real-world applications typically result in slight shaft misalignment, particularly the type of arrangement used in the gearbox assembly, that cause the rollers to skew. Consequently, the real-world rating life for full-complement bearings is actually lower than the published ratings.

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Hello Peter,
The original Drawn Cup Needle Roller Bearing used in this gearbox was a Caged Guided bearing. The other type is called a Full Complement, Drawn Cup Bearing. The Full Complement Bearing has no cage and a Full Complement of rollers (hence the name) to take up the space between the shaft and bore components of the assembly.

The rollers of a Full Complement Bearing rub together and tend to skew giving rise to typically 50% more friction than a Cage Guided type and 40% higher operating temperature at high speed. Accordingly, lubrication is very important with a Full Complement bearing.

Regards,

Bill

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Oh ! I see, you mean like the needle roller in the photo I’ve posted?
Peter B.

Hello Peter,
Yes, that’s a Full Complement Bearing.

Regards,

Bill

Thanks Bill.
I refer to “inner cage” or “non inner cage” hence the misunderstanding on my part. Norman obviously missed that I posted a “non inner”
Peter B.

angelw, I don’t know how you get a rpm of 14,685. The main shaft max speed can only be a function of gear ratios, the worst being for the 1st gear in a Gearbox with a ratio of 3.04:1.
Behind a V12 at a red line of 7000rpm, in 1st gear, the main shaft speed would be 2302rpm and the bearing speed would be the differential of the two as they are rotating in the same direction, thus the maximum bearing speed is only 4697rpm.
In 3rd gear that differential rpm. is only 1500rpm.

My mistake Norman. I used 2.993:1 (S3 1st gear) as the first gear ratio and omitted to apply the RPM of the Main Shaft. My point was, that the engine would have to have the heck revved out of it and the bearing wouldn’t achieve 5K revs.

Regards,

Bill

Dear all, thanks to all your pieces of advice, I could dismount the mainshaft and other shafts.
Now I shall have mainshaft and constant pinion shaft fixed, check all parts and replace all what needs to be.


From your experiences, what do you think of the aspect of the gears ?
Kind regards.
Christophe.

Still doesn’t explain a figure of 14, 685rpm, and I said a figure of less than 5000rpm, not an exact figure of 5000rpm.
Though my race engine produces max HP at 7500rpm.

Dear all, hello and many thanks again for all your comments and help.
I am at the stage of ordering the parts to be replaced : gaskets, seals, bearings and syncho rings.
I am just puzzled about the needle roller bearing between mainshaft and constant pinion shaft. Both are available and, from the discussion above, I do not know if I should order a caged one, as originally fitted, or a full complement one.
Kind regards.
Christophe.

Stick with the caged roller Christophe, it`s what Jaguar fitted.
What is the condition of the mainshaft spigot, photo perhaps?
Peter B.

Thank you Peter.
I just took the pictures.
Mainshaft end


Constant pinion shaft inner race

Finally the jam of needle roller bearing parts I found

I intend to have the shafts machined and sleeved as soon as I receive a new bearing.
Christophe.

If you play a oxy torch flame inside the outer cage of the needle roller, after it’s cooled the cage should drop out of the first motion shaft.
As has been advised check the layshaft countershaft.
Peter B.