Gearbox Woes!

[berry_jr]

My Interpol has developed a problem. It's making a whooshing noise reminiscent of a steam train! It does this with the engine off and in neutral coasting. Went from nothing to quite worrying in about fifty miles. Replaced the sprocket bearings, the outer was showing signs of wear. But the noise remains. Would someone like to confirm my worst fears? John Berry

[gripper]

Sound like it must be coming from the rear wheel or chain area. In neutral, engine off and coasting, the only thing turning should be the sleeve gear and all the back wheel gubbins.

[Richard Negus]

And, if the sleeve gear is turning, then so is the layshaft and three other gear pairs as well.If it's something where you can count the 'whooshes', then I would suggest something to do with the chain, requiring investigation ASAP.If it were something in the gearbox, I suspect you wouldn't be able to count or feel it due to the higher speeds involved. Take out the drain plug and see how much metal is on the magnet. With a cold engine and someone else's finger over the hole while you clean the plug, you'll only lose a little oil.My Commander has a resonance in the final drive, but that's because I was too mean to fit a new chain when I extended the rear fork. Instead, I fitted four new links in an old chain and suffer the inevitable consequence.

[berry_jr]

Thank you both for that. I'm inclined to think it's the gearbox output bearing, but, as per Richard's comments, the sound/rate does n't make me think bearing. I replaced the chain a couple of years ago when I put a larger rear sprocket on, so think chain problems unlikely. When I replaced the sprocket bearings recently, I have also reverted to the original sprocket, so plenty of clearance around the sprocket housing. Also checked the rear chain and all in order. Further investigation required!

[Richard Negus]

I replaced the chain a couple of years ago ...... think chain problems unlikely...... Also checked the rear chain and all in order

HAZARD ALERT ! I trust you used a new rivet link and not a spring link ?The pins on a spring link are longer than on a rivet link - the noise may be the pins catching on the gearbox casting.I know I've said this before, but using a spring link can seriously damage your health. They are less secure than a rivet link and a detached chain usually wraps itself around the rear sprocket, locks the wheel, and twists the rear fork, causing the rider to lose control. It's only happened twice to my knowledge, but one police mechanic was badly injured on a test ride.

[berry_jr]

Finally got the opportunity to look at the interpol again last night. With it running in gear with the wheel off the ground, getting the noises and could feel the chain jolting through the gaiters. Put the old chain on, just to confirm it was n't that and made no difference. Stripped it to the gearbox sprocket and could feel movement in the sprocket. So bit the bullet today and dropped the engine out. The maishaft case hardenning is failing where the sleeve gear runs on it. Its worn a recess of maybe half a mill. That's allowing movement in the sprocket and upsetting the chain run. Just got to get the bits and put it back together!

[Richard Negus]

John,Even for an Interpol, that's unusual! Does it have the needle roller bearing in the oil pump mount plate?If not, has the rear chain been too tight?How about a photo of the shaft end.R.

[gripper]

How many miles has it done? Did any Interpols have the outrigger bearing or would that have to have been a mod? Mine hasn't got it.

[Richard Negus]

Did any Interpols have the outrigger bearing or would that have to have been a mod? Mine hasn't got it.

John, Dave,Outrigger bearing introduced on IP2 part way through production, but I have no record of the actual changeover engine number. I'm confident that the last batch of MOD IP2's had it.All Classics and Commanders have it.If you take the oil pump cover plate off (3 screws), you can see the extra circular mounting plate, slightly bigger than the oil pump.

[berry_jr]

It does n't have the out rigger bearing. The sleeve gear needle rollers are intact which is surprising. I had expected the main bearing to have been the cause. I did replace some parts in the gearbox nearly fifty thousand ago, including fitting a second hand 5/8 main shaft. The bike has now done over a hundred thousand. Chain has never been too tight. The gearbox and drive has always been quiet and caused no concerns. I will try and take a picture for you Richard.

[berry_jr]

I've down loaded some pictures of the mainshaft.

[Richard Negus]

The wear marks on the mainshaft indicate that the sleeve gear is twisting and overloading the outer ends of the needle, causing the metal at that point to spall, or flake off. Note the greater weat at the outer ends of the marks and feathering of the inner edges of the marks.However, there are two sets of needle marks on the shaft. The other, older, set has the bearings further apart which would better support the sleeve gear, reducing the twisting and overloading.Is the tubular spacer between the needle shells missing, or too short?The bearing at the dog end of the sleeve gear should be up against the wire circlip, and the one at the sprocket end close to the oil seal.I'd also have a close look at the bearing diameter on the outside of the sleeve gear; if the gear has been allowed to twist, that bearing surface may also be damaged.Sketch to follow.

[Richard Negus]

Bearing specer.jpg

Dies of embarassment - can't spell SPACER!

[TRL]

Bearing specer.jpg

Dies of embarassment - can't spell SPACER!

or was that Circlip?

[berry_jr]

Many thanks Richard. It's an early Interpol, no sign of a spacer or ciclip! The mainshaft bearing has also failed big time! Just trying too get hold of the necessary parts!

[berry_jr]

Pics added

[Richard Negus]

John,With the two needle bearings close together, chain load would be able to twist the sleeve gear slightly and put extra loading on the corners of the large rollers. An ideal opportunity to convert to outrigger bearing spec. Whoever built the gearbox last time deserves a kicking! Not yourself, I trust?The large bearing is the same as old Triumph.

[berry_jr]

Afraid it was me Richard when I first got the thing and was the first time I'd been inside one! But it's done a reasonable mileage so I think that's acceptable. The sleeve gear has no spacer, circlip, or groove to accept one. It carries a Triumph part number. Would that have been fitted from new, or has someone replaced it incorrectly over the years? Not me, I put it back as it came apart. I knew no better!

[Richard Negus]

John,I think the very early IP2 5th gear was the same as the T140V (with a 57-**** part number), later similar ones had the circlip groove & spacer with a 69-*** number, improved material (EN36) and ground teeth. The last ones were outrigger type with even better material (EN39).With the rotary having almost twice the Triumph's torque, the rear chain pull would be almost double and skewing of the gear increased, causing the needle bearings to migrate. The outigger bearing stops the skewing and also gives better support to the spindly mainshaft.R.