80 S Gearbox

[ferog]

Hey guys,

Im having some issues with my gearbox, when it's cold it's worse, It's difficult to change down into gears, only have the problem in 1st and 2nd, I literally have to stop to change. That and I am getting alot of shuddering from it after it's placed in any gear. I realise it's probably time for a rebuild. Is there anything suggestable towards lessening the negative effect or legthening it's life? At this stage I am being as gentle as possible- Double clutching and not engaging gears when slowing down.

Thanks in advance.


Emma.

[80 nsw]

it could possibly be the clutch, shuddering, would mean that your flywheel may need machining, and the hard to select gears might be because the pressure plate springs are worn, and not giving you full travel of the clutch

[ozy1]

if i recall the clutch was only recently replaced in this, but you stil may have a clutch problem,

[J Top]

If it is only when cold try changing g/box oil for a modern 5 speed or synthetic oil, they both help to reduce " Cold Baulk".
J Top

[grub_80]

I had a similar problem but mainly with second gear. I replaced gearbox oil with good quality synthetic. Problem solved.

[dumbdunce]

I agree with the "clutch" diagnosis - if the clutch was recently replaced, it may have been damaged on installation, which is pretty easy to do when the gearbox is so heavy. Was the spigot bearing replaced? if not (or if it was damaged on installation), spigot misalignment can cause shuddering on engagement. Was the correct type of grease used on the gearbox input shaft splines? if ordinary wheel bearing grease was used, it can dry out and start to stick the driven plate to the input shaft, causing dodgy disengagement. The baulking in low gears is most often caused by incomplete clutch disengagement.

first thing to check is the condition of the clutch hydraulics - if there is any air, or the soft hose has gone extra soft, you won't get enough 'push' to fully disengage the clutch. if that's all ok, as a cheap dodgy "five minute fix", try lengthening the clutch master cylinder pushrod a few mm (two turns) which will marginally increase the clutch disengagement distance.

after all that, if you gearbox is fairly high km, it could just be that the synchroniser clutches are worn out and you'll have to get good at double clutching and rpm-matching to get it to drive smoothly. As others have suggested, thinner oil (maybe start with a 40/60 motor oil, or synth gear oil, or even as runny as ATF) might help, but the gearbox will be noisier as a result.

look on the bright side, at least your 80 isn't a pile of crushed scrap metal

good luck

Brian

[bruiser]

Don't know much about gearboxes but
If the problem was due to clutch faults would it not happen in all gears, not just first and second as stated?
Steve

[80diesel4play]

Here's the Secret Squirrel gearbox saver for 80's...

addin 3/4 of a bottle of Moreys, then top off the gearbox with Mobil 1 Synthetic. 15W-50. Simple - run that for about 2 changes and then switch to just straight 50w non synthetic. Works a treat and saves you @$2000 in rebuild costs.

The lighter weight wont clag your synchro's and will help down shift/upshift.

Shudder = worn clutch - get it looked at - have a tendancy to cause massive damage in the gearbox by vibrating the guts out of the input shaft and then foloow that damage through the box.

Cheers and good luck.

[80UTE]

Use and 75w80 gear oil Castrol EPX 75w80 works a treat if still difficult to shift the syncro's are worn and you can use ATF as it is still Extreme pressure gear lubricant . Engine oil dosn't have the correct additive's for gear box applications so should be avoided. I believe the service manual recomends 80w90 gear oil but this is too thick wont shift when cold and dosn't get circulated very well by the oil pump.Mind you if i had no other oil on the trail and i needed to get home engine oil is far better than no oil. This problem is a common prob to 80 gearboxes due to the physically large/heavy size of the gears, the syncronizer rings are working hard to syncronize the gear speed so the shift can happen. If the box has done in access of 150k it is highly likley that the syncro's need replacing if the shift is difficult with the correct oil. Word of warning thou if you start to crunching gears this can get real expensive as it as the gear syncronizer teeth and the shift hub can be damaged and this to properly fix can cost around $1000 in parts per gear/syncro/shift hub set. I have overhauled a lot of 80 gear boxes and most have been successful with a syncro replacement some boxes i have done have had worn/damaged hubs and gears ( bad crunching ) and a new syncro set has not fixed the problem. mean a second stripdown of the box to replace the gear and hub. ( This i leave for the customer to make the final decision, if i recomend a gear replacement its his risk if the box needs to be removed again stripped and gears replaced ) Caught out before and had to redo the job to try and save the customer some $$$$$.


Wally

[bruiser]

Yes good expensive oil will fix something that is f.............

[Mad Cruiser]

Ya reckon ????????

Didn't work for me

[bruiser]

[dumbdunce]

Don't know much about gearboxes but
If the problem was due to clutch faults would it not happen in all gears, not just first and second as stated?
Steve

clutch problems are usually most evident in 1st/2nd gears because of the higher percentage ratio differences involved; it is in fact pretty easy to change between 3/4/5 without using the clutch at all as the rpm differences are not that great, but to do it in the low gears requires far more care. Add to that the fact that usually when you shift into first, the vehicle is stopped, any problem amplified by a difference in rpm is amplified infinitely. also, you tend to use higher rpm in low gears, so not only is the percentage rpm difference greater, the numberic rpm difference is almost always greater, too.

in one sense you're right, if the problem is with the clutch, it will be present in all gears, BUT these problems tend to be masked in higher gears and far more obvious in lower gears. as it gets worse, it becomes more apparent in higher gears.

[ferog]

Yes the clutch was replaced with a heavy duty kit a month ago, Jeremy and I installed it ourselves, (used the grease that came with the kit) everything was new- The flywall didn't need to be machined we thought.

The spigot was lined up by eye also.

Syncro's is what was suspected for the difficulty in engaging 1st and 2nd.

The shuddering/vibrating after changing gears occurs in all gears. But the stiffness only 1st and 2nd.

Also when engaged in 4L 2nd gear crunches regardless sometimes it pop's out into neutral.

I have valvoline hp ls90 gear oil in atm which is the wrong one, have tried a gearbox treatment though.

Sounding like i have more than one Problem.

I will change the oil and try the techniques suggested and see how he goes.


Thanks again everyone for the input. Appreciated.

[low40]

there is no warrenty when flywheel not machined when fitting new clutch kit, not worth it for $40