What to do about my gearbox?

[bigbadbob76]

So.
My gearbox grates when selecting 3rd gear, both shifting up and down.
All other gears select quietly.
If I shift below 30mph and double declutch it's usually ok but shifting down from 4th going uphill is woefull.
I'm intending keeping it running as is until the winter and then doing something about it.
Not having the specialist tools may stop me doing it myself, though I can make some of the tools.
Not having huge funds may stop me sending it to Aidan. Though this would doubtless be the best way, quality costs money.
I'm wary of putting in an unknown 2nd hand box. When I bought the van it supposedly had a "new" gearbox fitted.
I knew about the 3rd gear issue when I bought it.
It's a 1986 dg engine, 4 speed manual van, so I think it's a 091/1 box. ?? according to the bible you have to remove the diff before removing the gear carrier on these.

I'm assuming it's a worn or broken synchro ring.

1: am I correct in this assumption?
2: is it a massive job to replace the ring? I have rebuilt a 2cv6 gearbox before so I'm not going in blind but....
3: What are the pitfalls for the unwary?
4: what other parts should I replace while I'm in there? main shaft bearing? 3rd gear? sychro hub?
5: what should I expect to pay for a refurbishment on my box?
6: what would you do in my position?

Any advice gratefully received (even if I don't take it. )

[itchyfeet]

can't answer many but no.5 was about 700 quid from Aidan 2 odd years ago for a rebuild.

You need special tools and jigs apparently.

[ZsZ]

1: probably. Best case scenario
2: disassebmling the gearbox to reach the ring can be challenging. And a few special tools are needed.
3: taking apart but unable to reassemble can be nerve-racking
4: full refurb: all seals, all bearings, all synchronizers, all clips, 3-4 hub and anything that worn. Minimal: big ball bearing, cheap needle rollers, seals
5: full refurb is starting from around 400 GBP in parts plus at least a few days in labour
6: I took apart my box a few times, it was scaring first but not as a big job now as I have some of the special tools nedded.

You can try making a puller for the housing then you can reach the gears without disturbing the diff and the double tapered roll bearing. On Youtube there is a polish guy who repairing boxes this way and Tigerbus had their box repaired this way in Turkey.
I had problems with my 2nd synchronizer especially using GL5 limited slip oils. (5speed box LS diff) Castrol Syntrans Transaxle GL4+ helped a lot with gearchange before I took apart my box.
If you decide to open the box then save some money for a spare gearbox if anything go wrong.

[ZsZ]

here is the Polish guys channel: https://www.youtube.com/user/kolo12/videos" onclick="window.open(this.href);return false;
here is the Tigerbus pic. I was wrong, it was in Mongolia where they used the puller:
https://www.facebook.com/TravelTiger/ph ... =3&theater

[colinthefox]

You can try making a puller for the housing then you can reach the gears without disturbing the diff and the double tapered roll bearing.

I have done a couple of boxes this way. You can only get as far as the third gear synchro ring IIRC, but that does look to be far enough to cure your problem. The major drawback with this method is if you get into the box and find the pinion bearing is loose, then you have to do the whole thing from the other end. The 3rd/4th hub is almost certain to have hairline cracks, so change it anyway. You can make a case puller from a bit of flat steel plate with a few holes in it. Mine's 19mm thick, but I would think 10mm would be OK.

I did what ZsZ suggested and bought a spare box before opening up. Then I did the spare.

[Aidan]

I'll happily support anyone having a go themselves, there's some excellent threads where people have made the tools themselves, the whole procedure is in the Bentley manual so you can clearly see what is involved and what to measure and mark and the community will provide help.

the 3rd gear worn out synchroring on a 4 speed is usually a symptom of the pinion bearing being worn allowing the back of 2nd gear to run against the back of 3rd gear pushing it into the synchroring and wearing it prematurely so expect to be doing the whole job; this isn't fatal on the four speed because there's no gear hung out the front, the same wear in a five speed means serious damage to 1st gear and potential major failure ; chances are it's already been apart before and done on the cheap previously or it was a used box that was fitted that was better than the one that came out but maybe not by much, if it has been repaired previously (broken synchro hub usually) then it was done without changing the synchroring, or the gear was damaged on the cone and the cone has then worn the new ring prematurely, I have dozens of 3rd change gears here that are fine apart from such cone damage; 3rd gear sets are not cheap unfortunately new and good used ones rare now

DO NOT pull the gear carrier off the mainshaft bearing, you will damage the bearing (it takes 2-4 tonne of force to fit it correctly and it should be replaced everytime) and you'll potentially damage the new bearing and synchroring trying to get it back together - in the field emergency repair to get you out of a foreign country fine but for a long life box no
DO NOT pull the 3rd 4th synchro off the mainshaft you'll probably damage the hub so if it isn't damaged it will be and that's another £100+

Your local gearbox place will probably quote £300 plus parts and do the best they can but without the correct tools and some measuring gear it will only ever be ish at that price and level of work, and there are few old school guys who have been doing these for a while (a lot had retired when I started hence the gap in the market for me to service) and the bread and butter work now is fwd parallel shaft/crown wheel boxes which are generally the same and easier to do, they may well pull the gear carrier off so unless you watch them do it you'll never know what has gone on; so many boxes I see have been taken apart by a blind man's dog with a chisel and put back roughly the same, now they are well cream crackered and to get them back to good is expensive.

The cases are getting well worn and corroded now, there's often a lot more to a rebuild than just fixing the fault
but don't let that stop you taking a look see

In the meantime double declutch if necessary into 3rd, do an oil change, run 75w/90 fully synthetic GL4 and add a molyslip GM6RA, it won't fix it but may make it easier to drive and seeing the drain plug magnet will give you an idea of the overall wear level since the last oil change which may advise your decision

[itchyfeet]

^^^ Thats why I never tried myself, proper complicated gearboxes, makes engines look like lego.

[bigbadbob76]

Thanks for all your replies guys. That's why I love this forum.
Thanks for your very detailed reply and for sharing your knowledge Aidan.
I'll have a good read and digest your info before making a decision on whether to go in there myself or not, I don't want to do more damage than good and then send you a box of scrap.
but an oil change and molyslip will be first on the list.
I just checked in the garage and the 5l of 75w/90 under the bench is GL5, bugger!! I've got a ranger box under there awaiting a rebuild too, and most of a spare 2cv6 box, this is becoming a collection.
I'll also drop you an e-mail re: pricing and timescale Aidan. If I book it in now for a winter refurb I might catch a slot.
Time to start a collection jar for the gearbox fund.

[bigbadbob76]

[quote="Aidan"]I'll happily support anyone having a go themselves,
Thanks very much for that, you give me hope.
there's some excellent threads where people have made the tools themselves, the whole procedure is in the Bentley manual so you can clearly see what is involved and what to measure and mark and the community will provide help.
I'll have a good read of threads and Bentley before committing myself.

the 3rd gear worn out synchroring on a 4 speed is usually a symptom of the pinion bearing being worn allowing the back of 2nd gear to run against the back of 3rd gear pushing it into the synchroring and wearing it prematurely so expect to be doing the whole job; this isn't fatal on the four speed because there's no gear hung out the front, the same wear in a five speed means serious damage to 1st gear and potential major failure ; chances are it's already been apart before and done on the cheap previously or it was a used box that was fitted that was better than the one that came out but maybe not by much, if it has been repaired previously (broken synchro hub usually) then it was done without changing the synchroring, or the gear was damaged on the cone and the cone has then worn the new ring prematurely, I have dozens of 3rd change gears here that are fine apart from such cone damage; 3rd gear sets are not cheap unfortunately new and good used ones rare now

Understood. great detailed explanation, cheers. not worth doing just a ring replacement.

DO NOT pull the gear carrier off the mainshaft bearing, you will damage the bearing (it takes 2-4 tonne of force to fit it correctly and it should be replaced everytime) and you'll potentially damage the new bearing and synchroring trying to get it back together - in the field emergency repair to get you out of a foreign country fine but for a long life box no
DO NOT pull the 3rd 4th synchro off the mainshaft you'll probably damage the hub so if it isn't damaged it will be and that's another £100+

From reading Bentley, I understand what you mean, don't pull, PRESS. I have a 10T hydraulic press at work and a lathe to make mandrels etc. so there's still (some) hope.

Your local gearbox place will probably quote £300 plus parts and do the best they can but without the correct tools and some measuring gear it will only ever be ish at that price and level of work, and there are few old school guys who have been doing these for a while (a lot had retired when I started hence the gap in the market for me to service) and the bread and butter work now is fwd parallel shaft/crown wheel boxes which are generally the same and easier to do, they may well pull the gear carrier off so unless you watch them do it you'll never know what has gone on; so many boxes I see have been taken apart by a blind man's dog with a chisel and put back roughly the same, now they are well cream crackered and to get them back to good is expensive.
Cheaper to knacker it myself than pay someone to knacker it for me.

The cases are getting well worn and corroded now, there's often a lot more to a rebuild than just fixing the fault
but don't let that stop you taking a look see
Yes, I appreciate rebuild is better than repair and that's what I'm paying for, If I do it myself I don't get piece of mind.

In the meantime double declutch if necessary into 3rd, do an oil change, run 75w/90 fully synthetic GL4 and add a molyslip GM6RA, it won't fix it but may make it easier to drive and seeing the drain plug magnet will give you an idea of the overall wear level since the last oil change which may advise your decision
Thanks, I'll do exactly that and consider my options.
Great advice well received.
Thanks again.

E D I T- Thanks for your e-mail Aidan. We might just have a plan.

[bigbadbob76]

It looks like I've got a plan forming.
I've sourced a DU box for not bad money, it was rebuilt in 2003 by Volkspares and has done 20k ish miles since as it was then laid up.
I've had the green light from Aidan (thanks for your help mate) and he's seen a pic of the drain plug magnet with just a light dusting on it, no big chunks.
Ok... so it's a DU not an ABD so has the slightly lower final drive but that might be a good thing,
I live 200 miles from the nearest motorway in a hilly part of the country so lower gearing might be an improvement.
When I do go on motorways I don't thrash it down the fast lane anyway.
Note to self... must order spigot bearing.

[itchyfeet]

Worth checking crank end float and clutch while you are in there, I'd have a look at gearlinkage gaiters too they are often gone, ideal time to do them.

[bigbadbob76]

Cheers for the suggestions Paul.
The clutch was supposedly done a couple of years ago when the G.Box was replaced...
There's an oil seep from the crankshaft seal which drips on the clutch, can you replace the seal from the outside? (think I might have asked this before. )
I have replaced the ball joint on the selector but will check the rest while I'm underneath.
MOT is due next month so I'd better get some overtime in.

[itchyfeet]

get some oil on your fingers if its gearbox or engine the small is verg different
If the oil seal has gone on the crank you will need to replace, leave it and eventually your clutch will be contaminated.

To do the oil seal clutch and flywheel has to come off.

page 2
https://club8090.co.uk/forum/viewtopic.php?f=37&t=140047" onclick="window.open(this.href);return false;

Don't make the same mistake with the clutch lever I made on page 3, tie it up before fitting the box.

[bigbadbob76]

Great link, Thanks Paul.
sounds like I might as well do the oil seal and shims if required while I'm in there.
seems not too bad a job and would be a bugger to have to do it later.
Do you re-use flywheel bolts?

[itchyfeet]

Do you re-use flywheel bolts?

I didn't at first but people have said it's fine so the last few engines I have reused, I only do the 110Nm in Bentley not the stretch setting in haynes.
If the hex is at all rounded bin them, check the tensile 10.9, 12.9 better