Thread: R380 rebuild after 5th gear failure

Ouch!!
I regularly use 5th when towing my 23ft 2300kg van with no issues thus far. It seems to cruise much happier in 5th than 4th where it seems to rev too hard. Done around 10000km's towing. I never let it labour in 5th and try to keep the boost at or under 15psi. I'm running Syntrans and have a larger transfer sump filled with syntrax.
Interesting to find the root cause of the failure.
Regards
Robbo

A mate of mine broke the main gearbox shaft in his 300TDI Disco. No one had seen one break before.

Originally Posted by awabbit6

Well it looks like our heavy camper trailer and the ECU remap were too much the Disco's gearbox. As we arrived at our camping destination last Tuesday a nasty rattle started coming from the gearbox. Changed back to 4th and it was silent. Into 5th - clatter, clatter, clatter.

I know that it is advised that 5th not be used for towing but the run down the highway from Beenleigh to northern NSW (Minnie Water) is fairly flat so I presume that it was already fatigued and the last crest was too much for it. We managed to get back without any issues (or noises) using by avoiding 5th

So I pulled it out today and this is what I found.









Teeth have broken off the layshaft in two places on 5th and the rear layshaft bearing has failed.
Tomorrow I'll continue disassembling to see what else I need to replace. The syncros on 1st to 3rd have been pretty clunky so I'm thinking a full rebuild kit from Ashcrofts for starters. I'm thinking of replacing the whole layshaft after seeing Pete's 90 snap one and mine has now been stressed. I'd rather not have to pull the box out again.

More photos to come ...

The extra umph that you got out of the motor has allowed you to push 5th when most of us would been going for 4th. But you don't need to have the extra power to damage the gbox, I have rebuilt my R380 due to lay gear failure and it is only behind a 300tdi.

Towing in 4th does not have to transfer power through the lay shaft/gears and therefore your best option to be sympathetic to your gearbox.

When my box let go I was not even towing, just cruising the freeway with a couple of 100 kg in the car.

All the best with the rebuild, a few threads with good guides and photos on here.

Paul
Out of curiosity what oil were you running ??
Does the vehicle have an oil cooler?

Duane

Originally Posted by awabbit6

Well it looks like our heavy camper trailer and the ECU remap were too much the Disco's gearbox. As we arrived at our camping destination last Tuesday a nasty rattle started coming from the gearbox. Changed back to 4th and it was silent. Into 5th - clatter, clatter, clatter.

I know that it is advised that 5th not be used for towing but the run down the highway from Beenleigh to northern NSW (Minnie Water) is fairly flat so I presume that it was already fatigued and the last crest was too much for it. We managed to get back without any issues (or noises) using by avoiding 5th

So I pulled it out today and this is what I found.









Teeth have broken off the layshaft in two places on 5th and the rear layshaft bearing has failed.
Tomorrow I'll continue disassembling to see what else I need to replace. The syncros on 1st to 3rd have been pretty clunky so I'm thinking a full rebuild kit from Ashcrofts for starters. I'm thinking of replacing the whole layshaft after seeing Pete's 90 snap one and mine has now been stressed. I'd rather not have to pull the box out again.

More photos to come ...

Originally Posted by djam1

Paul
Out of curiosity what oil were you running ??
Does the vehicle have an oil cooler?

Valvoline Duragear semi synthetic 75-85w

Yes it does have an oil cooler.

More dismantling yesterday and much frustration with cheap tools.
I'm going to buy a press this morning to finish pulling the mainshaft apart so I can replace the syncro baulk rings. It will make reassembly much easier too.





Just waiting on final quotes from Ashcroft then I'll order the parts.

Bugger...

Having done similar recently as well, I now use 4th/5th gear differently. Even though our TD5 has been chipped, upgraded intercooler, etc., I never push hard in 5th gear, towing or unladen. Down to 4th on anything other more than a slight incline, and often let the speed drop on slight hills.

I'd replace the layshaft while you're there.

I had a thread about my rebuild, but pretty much all the information I needed was already here on the forum, mostly from Pete.

Originally Posted by awabbit6

More dismantling yesterday and much frustration with cheap tools.
I'm going to buy a press this morning to finish pulling the mainshaft apart so I can replace the syncro baulk rings. It will make reassembly much easier too.
Just waiting on final quotes from Ashcroft then I'll order the parts.

I was able to pull mine apart with a Toledo hyd. bearing puller. I did have to make some longer tie rods for it though.

Cheers, Mick.