Drivetrain troubleshooting and overheating.

Took the horse down to Cavan for the hunter trial last weekend, disco loaded up likely to near max gross weight and then towing a very unaerodynamic 2.2 ton.

The temperature guage never exceeded half way but was down on power needing third year on some slight motorway inclines. Once i put the heater on full to give her a bit more cooling the problem was solved.

Viscous fan turning well, someone has fitted some electric fans also which were running too when i pulled over (never noticed them running before).

Never had any other overheating issues, not dirtying the oil, not using coolant.

Am i looking at a simple radiator clean out or is something else worth looking at?


Also, whilst 90 miles from home she made a load bang then wouldnt move without the difflock. The front prop would happily spin away so i took the front prop out, locked the centre diff, and she got me home ok. I expect a failed driveshaft or cv joint in the front axle. Do these parts come as a whole set, and is there anything else i should be changing at the same time whilst in there?

Many thanks for all input, and thank you again to the gentlemen who helped out diagnosing my brake issues.

first off check rad core is till complete and rad feels hot all over, if it doesnt you need a new one most likely the hot parts are the only bit cooling the coolant a rad that only cools partially is often ok till you start working the truck,top hose needs to be hot to prove thermostats open

So both front wheels spin freely without moving the diff input flange.

The diff flange wont turn in either direction with either wheel off the ground.

Am i right in thinking this means there must be something jamming the diff and a component failure on each side in order for both wheels to turn freely. Therefore the only way to proceed is to take the diff out, try and pull both half shafts out, and hope its not something too expensive that has failed?


Ive not yet taken it for a good run to get it warm enough to test the radiator.

If it drives in RWD only, ie centre diff locked and no front propshaft then either... 1. Both front halfshafts are sheared 2. The differential planetary gears and no longer in mesh, or 3. The final drive crown wheel and the diff hosuing is still working.

If the crownwheel and diff carrier can turn then you cannot easily check the differential action.
If you cannot turn the input shaft, then there could be a seized input bearing and the drive pinion sheared or stripped teeth. I think you are going to have to strip the diff out to be sure which means of course CV's out and halfshafts out...

Sounds like the planet wheels may have gone in the diff. When a drive shaft or CV joint goes, you normally heard it all the time, whereas the diff doesn't always make noise. (this is assuming you didn't take the drive member off the front wheel hubs)

Quite common for the diffs to give out on the planet gear pin, the gear snaps in half and drops to the bottom of the diff housing and everything moves freely (sometimes...) and yes, usually they give a very loud BANG as they go.

Simon098 said:

Sounds like the planet wheels may have gone in the diff. When a drive shaft or CV joint goes, you normally heard it all the time, whereas the diff doesn't always make noise. (this is assuming you didn't take the drive member off the front wheel hubs)

Quite common for the diffs to give out on the planet gear pin, the gear snaps in half and drops to the bottom of the diff housing and everything moves freely (sometimes...) and yes, usually they give a very loud BANG as they go.

Click to expand...

The bits highlighted in red are the bits I'm referring to.