Crunching still

Hi… hope someone can help!

S3 SWB 2.25petrol.
Third time of trying to get my gearbox working well, and it’s still not good.
Most previous issues have been sorted, but I am left with gears crunching the warmer the gearbox gets.

This is mostly from 4 to 3, but also 4 or 3 to 2.

When cold and for first 10 minutes say, it’s perfect. Then progressively gets worse. A lot better going up the gears.

My thoughts are;
1. It seems the oil is losing viscosity when hot to the point that the synchros don’t work properly…? Using EP90. Maybe there’s an alternative?
2. The 3/4 selector hub is a new Bearmach unit… maybe that’s a bad one? But it works ok when cold. I did think the unit was quite easy to slide on assembly… presumably the strength of the springs provides pressure for the synchro to do its job, before engaging the gear. If too weak, crunch time? Maybe the oil being thicker when cool allows the appropriate pressure.
3. Maybe, the clutch isn’t disengaging properly? Maybe it’s enough when the oil is thick, but not enough when hot… or the clutch when hot closes reduces clearance?

I have rebuilt it twice now. This time with a new main shaft. In fact, everything is new. Most NOS. The bearmach unit is probably the only non gen item…

Bit ****ed off tbh. I am tempted to try a more viscous oil… there’s an EP 100, and upwards… not sure that’s a good idea though.

Am I missing anything obvious?

I also have a fuel starvation issue… so, electric pump might be on the list. Also, I’m not entirely convinced the SimonBBC electronic ignition is great, seems odd as it advances up the revs.

Apart from that, it’s perfect!

That’s a shame was hoping it might have worn in by now

Might be worth having a look through these


Also seen in another forum the reverse fork could be not in best position on shaft and moving it forward helped stopped 2nd crunching

Simple thing first, check that clutch is fully disengaging.

steve2286w said:

That’s a shame was hoping it might have worn in by now

Might be worth having a look through these

Search results for query: Crunching gears

www.landyzone.co.uk

Also seen in another forum the reverse fork could be not in best position on shaft and moving it forward helped stopped 2nd crunching

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Ah, no, it didn’t wear in. This is after rebuilding it again… it’s quite frustrating

I’ve trawled all the forums for something similar… not seeing much to provide any clues tbh.

tottot said:

Simple thing first, check that clutch is fully disengaging.

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I’m pretty sure it’s ok. The clutch bite is quite high, the gears work fine initially too. I guess if the clutch is left engaged slightly, it’ll make hard work for the synchros.

I’ll investigate.

Spoke to a man in the know… he thinks to put the old 3/4 selector back, and check the Layshaft tolerance. If the Layshaft is tight, when warm could be dragging…

In theory you can change gear without a clutch and with very little or no crunching at all. I’ve limped home several times over the years with broken cables and the like.
Similarly on occasion I forget I’m in a tractor and crunch my series gears. Only now and then but only the once before returning to proven engine v transmission speed technique.

To check the lay shaft float it is box out, however if you reassembled with the original spacer washer it should be right. one issue is did you fit a new lay shaft rear roller bearing and was it fitted the correct way around?

If it's done a few miles and nothing sorts it, try a slop of Moly ...

tottot said:

To check the lay shaft float it is box out, however if you reassembled with the original spacer washer it should be right. one issue is did you fit a new lay shaft rear roller bearing and was it fitted the correct way around?

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Ah, it’s a “NOS” Layshaft, as reverse was buggered on the original, and not the original spacer but one I thought was right for it…

I am convinced the new roller bearing was fitted the right way around… but I’m obviously not very good at this.. lol

I did find it difficult to measure the endfloat, as it was instructed to grab the bolt and move back and forth… there’s movement in the roller bearing anyway, so i guess if I’ve done this wrong the clearance at the roller bearing end might be tiny, and closes when hot…, dragging and not allowing speed matching when clutch depressed? Does the Layshaft get pushed towards the rear when the gearbox is rotated? It’s a theory of what might be wrong I guess.

The Layshaft and 3/4 selector are the only bits unaltered from last time, so, I’ve decided to get in there again… and have splashed the cash once again on parts… I’ll have enough parts for a whole new gearbox at this rate!

I am fed up with lifting the ‘box out, so I’m adapting the crossmember to drop it out the bottom… for next time I **** it up… ha!

Dippypud said:

If it's done a few miles and nothing sorts it, try a slop of Moly ...

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I tried this last time… didn’t do anything to help. Is Moly ok with the yellow metals?

Yea the lift the bolt check only shows there is movement in the bearing if shaft is a tight fit in bearing.
Can not see shaft being pushed rearwards as it is held in place by the bearing/bolt unless bolt has become loose.

Im on my third BOX in as many years. rebuilt the previous box 3 times i think. Mike from Brittanica does a series box rebuild in a recent video,its well worth a watch as well as Geoffrey Crocker's gearbox build, maximus ironthumper has an excellent procedure for fitting it back in, and of course steam wally. In my last rebuild i had spent enough money that i took a chance on a 1st 2nd syncro unit with a small chip where the spring is, on the side that faces second gear. I now have crunching 1st to second and 3rd to second. If i wait until the speed is slow while holding the clutch in ,it minimises the crunch! hope that helps I feel yer pain.

findo1 said:

Im on my third BOX in as many years. rebuilt the previous box 3 times i think. Mike from Brittanica does a series box rebuild in a recent video,its well worth a watch as well as Geoffrey Crocker's gearbox build, maximus ironthumper has an excellent procedure for fitting it back in, and of course steam wally. In my last rebuild i had spent enough money that i took a chance on a 1st 2nd syncro unit with a small chip where the spring is, on the side that faces second gear. I now have crunching 1st to second and 3rd to second. If i wait until the speed is slow while holding the clutch in ,it minimises the crunch! hope that helps I feel yer pain.

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Hey, thanks for that… I’m not alone! Jeeze I’ve just splashed a **** tonne of cash on some more parts… so, I think, every part will have been replaced now with genuine parts apart from synchros… so it’ll be them..

I’ll check out the videos.. I’ve used steam wally so far.

I’m not going to give up… if it’s in and out a load more times… I won’t be defeated. Worst thing about this is it worked ok before I gave myself a winter project to recondition it, two winters ago. Keeps me busy I guess.

DeviousLandyGod said:

Hey, thanks for that… I’m not alone! Jeeze I’ve just splashed a **** tonne of cash on some more parts… so, I think, every part will have been replaced now with genuine parts apart from synchros… so it’ll be them..

I’ll check out the videos.. I’ve used steam wally so far.

I’m not going to give up… if it’s in and out a load more times… I won’t be defeated. Worst thing about this is it worked ok before I gave myself a winter project to recondition it, two winters ago. Keeps me busy I guess.

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One of the reasons I prefer to live with the leaks on mine. It would be nice to replace the seals but it works perfectly at the moment and I don’t want to tempt fate.

Bobsticle said:

One of the reasons I prefer to live with the leaks on mine. It would be nice to replace the seals but it works perfectly at the moment and I don’t want to tempt fate.

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I've mentioned it elsewhere, but those two seals that go under the bent tabs over the selector ball/springs are generally about a million years old when you buy them - and were the biggest leak on my current gbox. The heater hose is nice and squidgy and I don't even get mist around them.

(But I do agree with not touching what's working).

Beware the idea of increasing oil viscosity and/or using moly

The syncro surface have grooves and features to clear the oil away because the lubrication hinders the friction action of the cone clutch part of the synchro. This is often why you can get the odd crunch from even a modern gearbox when the oil is cold.