reverse crunch

[Trunkster]

Hi guys. Going forward threw all my gears is fine but when I put it in reverse I get a real good crunch. I only get this when the gear box has warmed up. Could this be low oil in box, how do I check the level and what is the best oil if it needs toping up? 1980 2.l air cooled!
Thanx

[Hacksawbob]

recomended oils is here
https://club8090.co.uk/wiki/Ge ... earbox_oil" onclick="window.open(this.href);return false;

if your not sure what's in there drain it and replace it.

https://club8090.co.uk/wiki/Ge ... drain_plug" onclick="window.open(this.href);return false;

[Trunkster]

Thanx Bob. Do you think low oil would cause the crunch as this only happens in reverse when gearbox is hot?

[croc]

Hi Trunkster
Just a point on gearboxes, reverse is the only gear that does not have synchromesh. (so gears engage without grunching - not refering to 4x4 vans!)
If the clutch does not fully disengage then the gears rotate and cause a crunch into reverse. All the forward gears have synchromesh to help stop the crunch by making them rotate at the right speed as you change.
Gearbox oil can affect this so check and change that first, its the easiest and cheapest - and good for the gearbox.
I have used 75w-90 GL4/5 in 5 speed and that works well for me.
The clutch comment gives you another avenue to check if an oil change doesn't resolve the problem.
Let us know how you get on with this.
Cheers

[ajsimmo]

When selecting reverse, try dropping it into a forward gear first, then out and straight into reverse (without lifting foot off the clutch). That should stop it grinding as all internals in box will be stationary.

[California Dreamin]

Good advice from croc...Bleed the clutch, make sure it is fully disengaging. Commonly refered to as 'clutch drag' where the friction plate is 'binding' and not fully releasing...either sticking on the splines, 'rusty or dry perhaps'.
Also...there are known issues with the spigot shaft bearing failure (the small needle roller bearing in the end of the crankshaft that supports the input shaft).
Changing the gear oil may also help mask this...using thinner 75W90 semi synthetic GL4/5 but perhaps won't be the cure.

Aidan Talbot is your man when it comes to all things 'Helical' & 'Spur'.

Martin

[Trunkster]

Well I took the drain plug out and it looked like a palm tree!! lots of swarf. Oil was brown and very thin. I have now done the oil change 4.2 litres in the gear box and .3 litres down my arm and over the drive!!! not had a clunk or a grind since so hopefully job done.

[Oldiebut goodie]

Easy to fill with a funnel and hose from the engine bay!

[Trunkster]

Hi guys. Lost first gear now too! I only loose first and revese when the oil gets hot ie driving around town for more than 5 mins. Took camper out for an hour on the motorway then round town for 5 mins and it was fine. Putting it into first when I first drive it is fine but after 5 mins I must drop it into first before I stop otherwise I have no chance. Reverse happens when it feals like it but double the culch seems to help! in and out of the other gears is fine all the time. what will sort this out?

[Aidan]

I'd suggest it's rebuild time, worn pinion bearing and shafts moving in case imho, no ammount of oil changes or additives will fix worn out parts
or you can buy a preloved box and hope that's ok

[Trunkster]

That sounds expensive! any idea the cost to rebuild it and have it fitted? too big a job for me to do!

[Aidan]

£900 upwards, no way of telling till box is stripped, could be almost double that depending on whether pinion shaft is damaged and what ratio it is and how many gears/shafts are damaged
check out JK, Engine Shop etc for exchange box price also Abbey Motors in Waltham Abbey advertise rebuilt exchange 5 speeds on ebay