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Diff lock?


 
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Doofus
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Joined: 07 Sep 2012
Posts: 12
Location: UK

PostPosted: Tue Dec 17, 2013 9:00    Post subject: Diff lock? Reply with quote

Morning guys. Bad day yesterday! Had to take my beloved '08 Landcrusier off road into a slippery wet grass sloping field with a one ton trailer hitched up. Just got into the gate and lost traction despite low drive and diff lock selected, all wheels spinning. Managed to reverse back and try again and this time got further before the wheels spun again; only this time the the weight of the trailer started pulling the back of the truck down the slope and I could do nothing to stop it jacknifing! The entire unit then slid down the slope jacknifed, until my front nearside came to rest against a tree! If the tree hadn't stopped me, the truck and trailer would have undoubtedly ended up in the lake at the bottom of the slope! So NS damage to truck from tree, OS damage to rear valance and mudflap from tailer going under vehicle, and tow bar and jockey wheel damage to trailer!! Managed to get 4x4 tractor to pull me out without more damage but even when I was back on the level I could not drive out on my own. The NS wheels were spinning and the OS wheels were not turning at all (confirmed by others watching); the tractor had to pull me right onto the lane before I could get traction. My question is this. I thought the Landcruiser was electronically equiped to deal with wheel spin but it did not seem to work, power was not transferred to the stationary wheels - why? And surely with diff lock on, front and back wheels should not have spun and OS wheels should not have been stationary?

Feeling pretty bad about the damage today and wondering if it was avoidable once the slide started. The grass was wet and the top couple of inches muddy before hard dry subsoil; once sliding it was like sliding on ice. I was cautious not to put too much power to the wheels and wonder if this is what I did wrong, would the electronics/diff lock have worked better if the wheels were spinning faster, are the electronics decided by speed of spin? Needless to say I was running on road tyres but I just imagined that the Landcruiser would have done better, is there any way to check the electronics/diff lock is working?

Look forward to your replies and advice.
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PostPosted: Tue Dec 17, 2013 9:00    Post subject: Google Ads keep this community free to join!


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petrolhead
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Joined: 09 May 2012
Posts: 62
Location: Cumbria

PostPosted: Tue Dec 17, 2013 17:15    Post subject: Reply with quote

Not sure which version (LC3/4/5) you have.
The central transmission diff lock ensures that power goes to both front and rear axels. This means one wheel will keep turning on each axle.
If you have a rear diff lock (locks the rear axle) this ensures that both rear wheels will keep turning, (normally you can only lock this after first locking the central diff), in effect you get three wheels driving.

I think (don't shoot me if I am wrong), that the LC4 and 5 only have a limited slip diff (LSD) on front and rear axels (and central transmission diff), the LC3 has rear axle diff and LSD front axle along with the central transmission diff.
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Glyn

2000 KZJ95 1KZ-TE LWB
Ironman Shocks and Springs
ASFIR Underbody Skid plates
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Doofus
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Joined: 07 Sep 2012
Posts: 12
Location: UK

PostPosted: Tue Dec 17, 2013 17:59    Post subject: Thank you petrolhead Reply with quote

I have the LC5 Invincible. I believe you are right in saying that this should have limited slip diffs front and back with central diff lock. The central diff lock only engages when low is selected and I had selected low and diff lock before going onto the slope. The real puzzle is that the limited slip did not seem to work at all (witnesses confirmed that only the wheels on one side of the vehicle were turning) and without knowing of anyway to check the limited slip diff I do wonder if it only activates when the spinning wheel on either axle reaches a set speed of revolutions, I intentionally kept the power off.
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munster
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Joined: 09 Jan 2011
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Location: Cheshire uk

PostPosted: Tue Dec 17, 2013 18:48    Post subject: Reply with quote

this might be worth watching, this is part 2 have a look at part 1 as well
http://www.youtube.com/watch?v=YNFacsKnswM
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LC 95 LWB 3.0TD, Cooper STT 265/75/16, Alien Snorkel, 40mm Ironman SL, 2000w inverter,Sterling Bat to Bat  split charger system, Diff breathers,HID 8" Spots,bootstorage drawers.TTI 1100CB, Terrain RTT+ Awning, K4 winch mount, Goodwinch TDS Goldfish winch
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Doofus
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Joined: 07 Sep 2012
Posts: 12
Location: UK

PostPosted: Tue Dec 17, 2013 19:26    Post subject: Here, take my money! Reply with quote

Great video munster - shows the problems really clearly. Loving the air lockers. But it seems to me that my electronic limited slip wasn't working as both nearside wheels were apparently spinning freely while the offside wheels didn't turn at all. Anybody got any ideas how to check the electonic limited slip?
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Glenn
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Joined: 01 Oct 2008
Posts: 153
Location: nottingham

PostPosted: Wed Dec 18, 2013 22:14    Post subject: Diffs Reply with quote

Firstly your LC5 has open diffs in the front and rear axle. The rear diff on the lc4&5 is Not lockable like the LC3. But the LC 4&5 have traction control.

All 3 models have a Torsen centre Differential ( try google) with an electric actuator, this Will lock in High and low range.

In the situation you describe with both NS wheels spinning I bet there was No TC light flashing on the Dash?  This is because it needs a Boot full of revs to get the Traction control working It will then brake the spinning wheels, the TC light will flash But you will hear the TC working.

I find sometimes you have to rev up to around 3000rpm to get it to work and then release the gas to tickover, then back on the gas to obtain traction. Also the system seems to work better with the center diff unlocked, tend to go sideways less. Smile
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Doofus
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Joined: 07 Sep 2012
Posts: 12
Location: UK

PostPosted: Thu Dec 19, 2013 0:34    Post subject: Traction Control Reply with quote

Thanks Glen, you're right about the traction control light not flashing and I didn't hear the brakes cutting in on the wheels that were spinning. I think that also engaging the central diff lock did promote a sideways slip that the laden trailer turned into a jacknife from which there was no recovery on the slippery grass slope.

Does the traction control also work on the transfer box when either the front or back wheels are spinning, or can this only be controlled using the diff lock? If it is best not to engage the central diff lock on sloping wet grass, is the only time to engage it when driving on level but slippery surfaces such as mud, wet grass or ice?

The key also seems to be that even the best traction control or diff locks are only as good as the traction provided by the tyres which begs the question, what are the best tyres for alround road use with occassional use offroad mainly on mud, wet grass or tidal slipways?
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petrolhead
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Joined: 09 May 2012
Posts: 62
Location: Cumbria

PostPosted: Thu Dec 19, 2013 10:48    Post subject: Reply with quote

Views on tyres is split on the forum, If you have the funds BF Goodrich A/T all the way for me, great mileage from them too !!
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Glyn

2000 KZJ95 1KZ-TE LWB
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Glenn
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Joined: 01 Oct 2008
Posts: 153
Location: nottingham

PostPosted: Thu Dec 19, 2013 18:38    Post subject: Diffs Reply with quote

Traction control can't be switched off but it does work better with the center diff not locked. When the Diff is locked it deactivates the stability control though.

Tyres If you have Dunlops fitted they are useless offroad. I had General Grabber AT2 on mine for 2 years, Super all round tyre, but I made the mistake of fitting 265 70 17 instead of the original 265 65 17.   They made the speedo correct but the odometer read slow. also cost about 4 mpg.  I went back to Goodyear Wrangler 265 65 17, not as good off road as the generals but 100% better the the Dunflops.
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Doofus
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Joined: 07 Sep 2012
Posts: 12
Location: UK

PostPosted: Thu Dec 19, 2013 22:26    Post subject: Reply with quote

Thanks again for the advice.

I'm still confused about when to use the diff lock?

I used to run my Jeeps on Wranglers and found them great alround tyres. I am less than impressed with the Dunlops fitted on the LC, although they did do alright last winter on icy roads. Even though they have tons of tread left I will probably change them for BFG AT's or GG AT2's as recommended. Glen, how come your 70's made the speedo correct but the odometer read slow?
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Glenn
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Joined: 01 Oct 2008
Posts: 153
Location: nottingham

PostPosted: Fri Dec 20, 2013 18:07    Post subject: speedo Reply with quote

Easy Very Happy  in standard form all speedos read about 5 to 10% to fast but the odometer is about right, so buy increasing the overall gearing the speedo slows down along with the odometer.

With the 70 profile tyres the speedo agrees with sat nav and all the roadside waring signs, on a know distance of 70 miles odo reads 68 miles

With the 65 profile standard size tyres the speedo reads 33 satnav and roadside signs say 30 mph,  my know distance of 70 miles reads 70 miles on the odo
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