Strengthening the front diff/axle.......

[Lorin]

Right, not wanting to kick off anything here but.....

There is a fair bit of evidence suggesting that the only significant weakness in the 80 drivetrain is the front diff - Oz forums often describe them blowing even without serious abuse. Our plan is now to ship the 80 to Oz in 2013 to do 6 months of serious offroad trail driving. The truck will obviously be pretty loaded/heavy with a LR tank, fair amount of water onboard as well as all the required camping gear etc.

Now I know that there is an argument that driven carefully we shouldn't have a problem and that by strengthening the diff you just transfer the stress somewhere else. However, I am all for sorting things before they have a chance to occur wherever possible and I'll take my chances with the whole stress transfer bit. So, I am investigating my options for strengthening the front end.

Ozzie forums often mention installing the front diff from the Nissan GU patrol but there is scant little info on what exactly is required - I have posted on Offroad 80s to try and find out more. I am interested in hearing what other options there are. I assume one would be to install cryo treated gears and Longfield CVs but is that all that would be required and are there any other options

Any advice greatly appreciated

 

[Chris]

Well someone has to say it first....


Paging Doctor Wildsmith. Doctor Wildsmith to the white courtesy phone...

But before he does, one option would be just to have the front diff in perfect condition. I suspect that many that blow are well past a nip and tuck treatment and having any out of spec part such as preload would give any torque loading a but of a run up ending in failure. I don't think it would be fair to call them weak (which you didn't), they are the weakest point perhaps, but not weak.

Was off roading on Sunday. Two lads in a Bobtail Rangie blew their rear diff in a bomb hole. We rallied round and someone produced a spare diff!!! Within the hour we had it back in and they were off. Within 5 minutes, they had broken that one too and went home in 2x4. Now that's weak

 

[Lorin]

..... one option would be just to have the front diff in perfect condition. I suspect that many that blow are well past a nip and tuck treatment and having any out of spec part such as preload would give any torque loading a but of a run up ending in failure.

Yep I totally agree with you there. The plan is to re-gear the diffs to run 35s next year, so in the very least they will get a full service and rebuild. Will be interested to hear Jon's views on what the options are.....

 

[callum]

To be honest, your best bet is probably just to deal with it if it does go. There are thousands of 80's rolling about the outback all on standard diffs which no doubt have been doing it for years. With that in mind, if the problem was really that bad, you'd hear a lot more about upgrading. I don't want to underplay things, but australia is a 1st world country and its full of landcruisers so you'll get the bits without too much bother.

The main weakness of the front diff (aside from its size) is the fact that its reverse cut. This makes it pretty strong going forward, but more likely to spit the pinion and strip the crownwheel in reverse. Most of the failures of this diff will be reversing out of trouble and most likely in a comp situation. As you're not competing, try to avoid difficult reversing, take your time and bring a tirfor or such to help.

If you really want to upgrade, you could look at cryo-ing the diff (some folk swear by it) or as they sometimes do in iceland, replacing the centre with a 60 centre, which is 9.5" like your rear diff so a bit more stout. By replaing the centre, i mean cutting out and changing the middle bit of the axle casing, so its quite a bit of work. I daresay you could stick a gu axle on the front, but it seems like an awful lot of effort to go to and you're mixing manufacturer's parts.

Hope that might be of some help, if maybe not quite what you were looking for.

 

[Jon Wildsmith]

I think Ian is the man to talk to, he has collected a fair amount of data on how to break them For your intended use Lorin I can't see why you'd go to the expense / trouble of switching over to a patrol diff or something more exotic vs a well built standard 80 series unit. At least with the standard unit it's easy to source a replacement if the worst happens. I don't think an in spec diff is weak, but once the bearings have worn a bit everything can move more than it should and then the gear contact becomes sub optimal and bits fall off. As callum mentioned, hypoid gears have a strong side and a weaker side but at least the 80 has a reverse cut front gear set so it's strongest going forwards which is why we say not to do recoveries in reverse.

 

[frank rabbets]

Hi
Is the rear diff also weaker in reverse?

Frank

 

[pugwash]

lets not get carried away- the front is far stronger than the equivalent rover item!

having now done 2, my third seems to be holding up very well, but for one major reason i beleive- its been totally rebuilt and without the crush tubes- this has left the pinion very very stable. For me, on the previous 2 diffs that broke it seemed like the pinion had considerably lateral movement- so what clearly happened is that the pinion was only contacting the outside of the raing gear teeth.

Persumably You could have the same problem if you had movement with the ring gear.

One way of solving it (whilst keep everything stock), would be to install diff peggs- a common upgrade on competition rover diffs- ashcroft transmissions do it: http://www.ashcroft-transmissions.co.uk ... oductId=63

 

[Jon Wildsmith]

Is the rear diff also weaker in reverse?

Yes, but it's a bigger gear set so this is never a real concern. The 'weak link' on the rear is the drive shafts twisting not the diff.

IIRC LR's (pre D3 at least) use the same diff front and rear so whichever direction you go in one of them is running on the weak side and they're not all that strong to begin with!

 

[callum]

there's a reasonably good explanation here...
http://katy.tx4wd.org/tech/general_axle_info.htm

60 series axles were low pinion at the front, but of course were bigger. Better for reversing out of trouble, but a bit annoying for packaging your steering and clearance. I suppose you can argue the merits of either approach, generally the axle at the back end of the direction you're driving in will be taking most of the strain, however in the 80 axle's favour, its designed for and already installed in your car.

With regard to rover diffs, they are mostly spiral bevel, but the salisbury axles were hypoid and of course much bigger. It gives you a clearance advantage, but as i'm sure many can attest to, rover diffs blow quite often.

Longfield cv's are not warrantied for road use, so before you spend the money you probably want to consider what mileage you're doing vs how tough the off roading will be/ how stuck you will get.

 

[Matt Wright]

Lorin, in total layman's non technical terms, we never saw anyone with a problem with an 80 diff anywhere in Africa and there's some pretty (verrry) mean tracks there. Can't comment on the 35's impact but 2 points - Standard as possible / self sufficient is always very useful and, the 35's may not give you as good consumption / what's the benefit?
We ran a brand new set of BFG KM2 33's which were awesome and are till on the truck. Even more efficient wold have been the All Terrains but it's 6 of 1 overall given the difference in terrains we encountered..
PS, we couldn't find a spare tire bigger than 31" in Central Africa which is pretty "built up" so 35".. Even less likely and they'll be $$$ in the bush defo take 2 spares!
See you at Lincomb!

 

[Lorin]

Thank you for all your advice.

The consensus across here and from other forums (Offroad80s and IH8mud) seems to be to stick with a well built standard diff with maybe just the addition of a solid pinion spacer. The issue of whether cryo treating is really worth it or necessary isn't clear cut so I reckon I'll think a bit more about that. Otherwise, I'll simply stick to standard and make sure it's all tight and new.

 

[Matt Wright]

Sounds good.. simple = best IMHO
So, no africa?? You going to aus instead.. Take plenty water and watch out for the killer "drop bears"!

 

[Lorin]

So, no africa?? You going to aus instead.. Take plenty water and watch out for the killer "drop bears"!

Yep, will explain more at Lincomb but basically due to wanting to maximise the potential for offroading and rough camping whilst minimising the potential stressors due to safety concerns(snakes, spiders, sharks and crocs aside). I've driven some of Australia's best trails a while back in an old FJ45 but there are loads more I'd love to drive and a few I'd like to revisit with more time and a more capable 4x4

So what's a "drop bear" then....

 

[Matt Wright]

http://en.wikipedia.org/wiki/Drop_bear

 

[Lorin]

 

[Chas]

Don't laugh Lorin, when I went to Australia I was told to spread Vegemite behind my ears . . . and I wasn't attacked by the Drop bears once!

 

[Dave2000]

I think anything that could be said about the front axle has been said, I have replaced a couple, one was a client pulling a tree out of the ground in reverse, the other I cannot remember but it was in reverse. I am inclined to go with current thnking and leave the OE in there however, I would also be inclined to pull it out and stick some 'blue' on it and check the contact areas, adjust if need be and put it back wit a decent quality oil. I also remember reading that if the hypoid oil is contaminated by the CV grease it weakens the shear strength of the oil and increases wear ect?

FWIW, if your car is auto they also tend to be kinder to the rest of the transmission, but I have driven my manual quite hard and have yet to break anything................there goes me with my big mouth

regards

Dave