Series diff question

[Anderzander]

I have a transmission wind up type question.

My friend is overseas in his series and has snapped a rear half shaft - whilst the new one is making its way to him - he’s using it in 4wd.

After about an hour of driving or so he gets a clonk - which he described as almost like a gear slipping on the front diff.

So I guess the question is - can you get transmission wind up with only one half shaft in the back ?

My understanding is that 4wd in a series is like centre diff lock in the defender, ie both propshafts lock to turn at the same speed.

.. and that normally they turn at different speeds - and together with the diffs enable each wheel to turn at a different speed as you go around corners…. And that locked together you can get wind up where the wheels can’t slip to release it.

However - with one half shaft in the back - wouldn’t the rear diff put all the drive from the prop to the side of the diff that would just spin freely ? 

Anyone explain what’s happening to me please ? 

 

[steve b]

There could well be a problem in the front axle that only shows once warm ? Or possibly the 4WD front end of the transfer box.

With one rear half shaft it can't wind up   

I assume all the debris is out of the rear diff ? 

Steve 

[Anderzander]

Diff has been pulled and cleaned out. 

I think you’re on to something with a pre existing fault. It’s possible they 4wd high hasn’t been used much - just short stretches of 4wd low and the rest of the time it’s high range rear wheel drive. 

[Hybrid_From_Hell]

It cannot be wind up but all the power is going to front axle only 

this will feel strange at best but  on tarmac vs dirt roads it will be worse 

the rear prop is still being powered and driving a diff / broken at speed …who knows what’s going on in there 

 

if he has to continue I would suggest remove rear prop

[Anderzander]

Thank you ! 

[Snagger]

The Series 4wd system uses a dog clutch to lock the front output shaft to the rear shaft for drive; there is no differential or clever coupling, just this sliding collar to couple or uncouple the two shafts.  The teeth are very coarse to allow plenty of play so that they will not bind when engaging or disengaging on the move.  
 

I think it’s likely that he is hearing that front output backlash in the coupling make more noise when the oil is hot and providing less cushioning to the metal, nothing more.  He might need to check the levels or even replace the EP90 - it is often neglected but breaks down with age, and one of the key jobs in EP oils (the added sulphur that creates the brown residue it leaves and the foul smell) is to provide that impact and extreme pressure (the “EP”) that coarse gears and splines cause.  Many series owners use W75 (Roamerdrive specify it) in the belief that it is a good or better modern equivalent, but it lacks the sulphur and cushioning effect.