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lj70 rear axle-where have i gone wrong??

rikm777

New Member
Joined
Feb 22, 2011
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47
alright this could be a fairly long and rambling post but hopefully someone can enlighten me as where i gone wrong.i bought a rear axle from a 1992 lj78 with factory diff lock and disc brakes to fit on my 1988 lj70.it has been mentioned on a few previous posts that this is a straight swop
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it arrived this morning and i had a chance to compare it to my existing rear axle
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the set up is totally different as you hopefully can see.the radius arms bolt into a different position and it is set up for both the shocks to bolt onto the front side of the axle rather than one in front and one behind like my current set up.
Does my round headlight earlier lj70 have a totally different rear axle set up from the later square headlight lj70 or is this a totally wrong axle.it seems the same width,the diff casing appears to line up with the prop and seems to have the same bolt pattern.i,ve been assured its from a 92 prado
now i know this can all be sorted with a hammer,angle grinder and welder,but now i,m wondering if this is compatible with my existing front axle with respect to ratios

while i,m at it does anyone have a wiring diagram for the rear locker.i,ve got the dash mounted switch which has two thin wires coming from it and the cable attached into the rear axle has 6 wires of various colours
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i know there would normally be a series of locked and unlocked light flashing on the dash.this motor is not going to be used on the road and i just want to have it on or off.i dont have the diff lock symbols or lights on my dash
final point.having paid for this axle and had it delivered i was informed that when they sell a complete axle they obviously dont include the calipers (they had sold them already)which i was not incredibly impressed with as i dont think the drums on my existing axle will not bolt onto this axle.if anyone has a set of calipers from an old axle for sale i,d be most interested
any help would be much appreciated
 
I am no expert on this stuff, but what I can tell you (if you don't know) is how the locker motor works. This might help you with the wires. The locked / unlocked indicators come from a small switch on the top of the axle usually. This really is a simple contact switch. You could easily wire that to a light to indicate locked position. You might need that - just hang on for a sec and I'll get to why.

When you turn the dial or flick the switch - whatever, the 4x4 ECU only runs the motor for a couple of seconds. This winds up a clock spring in the locker. When all the teeth etc align in the diff, the energy in the spring shoots the locking mechanism across. If you wire it in bypassing all the clever Toyota electrics you will need to recreate the timing for running the motor. If not, you will simply destroy the inside of the locker. You can't trust to running it by guesswork, I don't think. Now, you might be able to get some sort of timer made up that will only fire the motor in short bursts, say 1/4 second. Then using the light on the dash from the locked switch you'll know when it is locked. Once you get that working, you might know better how long the motor needs to fire for. The motor drives a worm gear so there is considerable torque in there. If you over run it against the stops on the spring it will simply shear the teeth of the main gear wheel. The diff can take quite a bit of lining up before the lock comes on. Don't keep firing the motor if it's not locked.

Sorry if that's a bit pants. JW will perhaps have a better suggestion on how to configure a locker motor timer 'cos he's a genius. Just pointing out what goes on in the motor in case you didn't know. If you did, sorry - I'll STFU. :roll:

Chris
 
thanks for that Chris.even though i run my own electrical business i,m an absolute chimp when it comes to auto electrics.i wasnt aware of this timer set up i thought it was just a case of energising or de energising a solenoid.this is all very helpful tp me.no ecu or indeed any electronics on mine so i,m guessing that i will have source something to set up this arrangement if if dont what the diff destroyed instantly
 
Oh no, hope you manage to get some answers, I have the same 1988 model and had the same plans, spoke to a guy selling 2 axles today from a 78 import, thought it was plug and play! Good luck
 
yeh Simon.its looks a very long way from plug and play.to use this axle i,m gonna have to cut both the shock mounting brackets and radius arm mounting brackets off my original axle and weld them onto the new axle.i,m not 100% sure that the cup that the coils sit into are even in exactly the same place.unfortunately the breakers i got the axle from was at the other end of the country from me so i took a punt that it would be right (based on numerous posts that said it was!!)and just got them to send it down.oh well i guess its another opportunity to improve my limited welding skills
 
I do hope the diff ratio is right for your front axle. Going to be a bit tricky if it's not.

Your profile doesn't say where you are n the UK. It helps if you fill that bit in. It makes it easier to find someone to help you out - like with welding!!

Chris
 
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I would question what that axle came off. You must get matched ratios front and rear as Chris said so to check you will have to take both diffs out.

So the easiest way would be to just change the diff as the diff locker mechanisam is on the diff carrier not the axle case.

If that works that would save a lot of safety critical welding
 
the diff casing on the axle with the locker is physically larger than my existing one with the lsd .it doesnt look possible to swap the the diff with locker into my existing casing.unless someone knows different?
 
I very much doubt it will be the same ratio than your current one then
 
From the description you've given and pic I'm pretty sure I can confirm it is an LJ78 axle you've got... but I'm amazed at how different your original axle is! The ratio in the new diff should be 4.88 if it's off a 2.4, so check that against yours. On the plus side you should improve your articulation a tad if you can get it to fit, with having the radius arms closer together and both shocks in front of the axle ;)

Click my sig pic for my build thread, I think there's some pics from when I did my suspension lift of how my rear axle's set up ('92 LJ78 w/rear locker) if that's any help. [Edit: on the 3rd page]
Good luck with it mate.

Jim.
 
The actuator has a position 'sensor' (tracks that a contact moves along) so you use those to control power to a relay which in turn controls power to the motor. So some of those wires are a direct motor connection and some are the position sensor and then there's also the 'locked' sensor switch Chris mentioned. No timer needed, just some relays and a wiring diagram :)
 
well having spent hours trawling the american hilux and diff info sites i,ve managed to form a workable plan to use this e locker on my lj.this information might be of help to you Simon if your gonna go down this route
1- Jimbo i wish i,d studied your rear suspension rebuild thread before hand cos it shows quite clearly the totally different for shock mounts etc.this is not a problem though because all i,m gonna use from the lj78 axle is the e locker and its casing.the other part of the diff casing which is attached to the beam only seems to require minor modification for the e locker to fit- a couple of little bits ground out and a couple of studs repositioned.the nice american chaps have provided plenty of pictures showing where you need to alter the casing
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2-This site also rather helpfully has a couple of DIY wiring diagrams for the e locker which confirm exactly what you have said Jon
 
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this the easiest way to wire the e locker just using a dpdt(double pole double throw) switch which gives you only a locked light,but can be done for pennies.there is a slightly more complicated version ,but not by much which uses 2 additional relays to reverse the polarity to the locker motor which would allow you to have all 3 lights to show locked,unlocking and unlocked
all this info came from a wonderful american site called Erik,s toyota differential info http://home.4x4wire.com/erik/diffs/
Providing the diff ratios and drive shafts are the same on both axles it should be a fairly straight forward job
if you go down this route Simon feel free to contact me because although i dont claim to be a font of knowledge on this(yet!!) or particularly capable with a spanner i can guarantee you thing.Any time consuming head melting problem that you,re likely to come across i,l have been there and as they say" in the land of the blind the one eyed man is king" :?
 
whilst i,m on here and totally off on the tangent.i,m looking for someone down my way to fabricate a winch bumper for me something similar to the one on my hilux surf.the guy who owned this before me made it himself .i think he based the design on something he,d seen on an american 4x4 site.any help much appreciated
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Glad you have found a solution to get it to fit, would be interested in those website links if you wouldn't mind, will pm you as soon as I find mine. Looking forward to your updates on how it goes, good luck
 
On the KZJ70 the rear shocks are mounted forward and use threaded pins and 2 rubber mounts per side.

Roger
 
Rik

What about the guy you bought the surf off? Couldnt he do you a bumper.

Pete
 
Fabricating the diff housing is doable but I would modify the new LJ78 diff housing to just fit under you LJ70 that way all original internals .The reason being the splines of the short axle are actually longer but still 30 splines . The locker actuator or swivel will not move far enough to disengage from the lock position.
 
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