LJ70 Build Thread!

[sae70]

Sods law m8 It's always the way with me as well!!! Working on the truck to last moment before any trip

Good luck to you

 

[Ben]

Thanks Steven.

going to go and strip it all back down again now, in the rain!

Im not a trained mechanic or engineer, so I guess im bound to f*** things up from time to time when doing these jobs on my truck.

Important thing is i learn from it, so hopefully i dont make the same mistake(s) again!

 

[Ben]

Damm im getting quick!

29mins from driving the truck round the back of the house, to this point!

Didnt stop to take [strike:3nfwkc7w]hundreds[/strike:3nfwkc7w] any pics so that sped things up a bit.

The hilti impact gun speeds things up massively aswell!

Not sure i could strip a diff out that quick in the middle of the outback, or in a jungle on the rain forest challenge though.

Oil looked ok, and didnt smell burnt.

Got the diff on the bench to have a look.

First thing i noticed was some scratches on the ARB centre.

They dont go all the way around, only about half way.

Any ideas?

Turning the ring gear and shinning a torch between the pinion gear and the bottom of the ARB centre, theres a clear gap all the way around, so I dont think its a clearance issue.

Is it because ive set it up wrong. ie. got the bearing preload wrong?

or is is because the bearings are knackered?

Lack of experience with stripping and re-building diffs is certainly slowing me down in diagnosing the exact problem, and putting it right.

So any advice/help would be appreciated.

 

[adrianr]

can you get hold of jon wildsmith - pm perhaps - he is the diff doctor

 

[wobbly]

Ben, off topic slightly, do i recall you had problems with brake discs, where they the milners ones?

 

[Ben]

can you get hold of jon wildsmith - pm perhaps - he is the diff doctor

Hes on holiday in Switzerland.

Ben, off topic slightly, do i recall you had problems with brake discs, where they the milners ones?

Yes there shit dont buy them!

Just spotted your going to get some new rear discs for the back of your 90.

If there anything like my front ones were, then you may need a press to get the old disc off the wheel studs, and then the wheel studs back through the new disc.

Maybe I wouldnt have had issues if id used genuine parts, but certainly using the milners bits i had issues.

 

[hairyguy4]

what was the plan for the bits of metal you were going to pick up? home made ground anchor? also a bit off topic but when you rebuilt your front swivels, did you have any shims, as im doing mine and there are none fitted but with a bit of reading nivapilot didn't have any on his neither

 

[Ben]

You will have to wait and see!

Unfortunately doesnt look like i will be able to start on it this week now.

need to get my truck fixed first!

then need to remove the front passenger seat and fit my bed, and sort all my camping gear out.

I am very excited about this project i want to do.

I can picture it perfectly in my head and know it will turn out and work perfectly!

Regarding front shims, none were fitted on mine, and i didnt fit any either.

I did buy some from milners just encase, but i never followed the procedure in the FSM to determine what size shim is required.

Interestingly enough though, when i bought a front axle off Karl,which was off an earlier 70, to replace my cracked ring gear. I striped the axle totally of all usable parts, and found that it had got a few shims fitted both sides.

Seems almost like Toyota fitted shims to earlier 70's but them didnt bother on later models?

 

[karl webster]

I was hoping jon would pop up for you ben before you stripped it. Got no idea with diffs as i havnt done anything at all with them. If you have the marks only half way round surely that would indicate that it isnt sat in there true? Or something is slightly bent perhaps/?

 

[Ben]

Yes very true Karl.

I wonder if one/both of the bearings have got play in them, which is causing something to oscillate, and so only hit in certain places.

Im also concerned about the heat i was getting through the axle.

As Graham said on the previous page, for the outside of the axle to be too hot to touch, then the inside must be very hot.

Nothing looks blue though, and cant see any signs of overheating.

People have said that the axle shouldnt get too hot to touch, hence why ive pulled the diff out to see whats wrong.

 

[adrianr]

going to take a guess here - if there are marks like that suggests that part of the diff is off centre.

is it possible big ring you heated with hot water to fit is not 100% seated causing a slight oscillation?

 

[username_11]

Because the locker body is bigger then a normal diff the clearance to the pinion can be very tight. grinding the edge/end of the pinion can be necessary (was on one of my diffs) .

it may have only rubbed in reverse, because the pinion will be pulled into the diff


i also felt my diff when i got home from work. 70mph, up hill and it was fairly hot but i could hold my hand on it easy enough, so not scalding hot. hypoid diff's by there nature will generate heat

 

[Ben]

I feel a bit better about my diff situation now!

I think half the trouble, when i set it up before, was that i didnt really understand what the FSM was saying, so i struggled to follow the instructions fully.

Hence why i wasnt confident id set the bearing preload correctly, or got the ring gear back lash spot on.

So tonight i stripped it all back down, and started again and followed the FSM to the dot!

Suddenly everything clicked into place and i understood exactly what the FSM was saying.

Im now 100% certain ive got the ring gear back lash and bearing preload spot on.

going to take a guess here - if there are marks like that suggests that part of the diff is off centre.

is it possible big ring you heated with hot water to fit is not 100% seated causing a slight oscillation?

Its possible, but im 99% certain it was seated correctly. I also made sure both mating faces were spotlessly clean.

Because the locker body is bigger then a normal diff the clearance to the pinion can be very tight. grinding the edge/end of the pinion can be necessary (was on one of my diffs) .

it may have only rubbed in reverse, because the pinion will be pulled into the diff


i also felt my diff when i got home from work. 70mph, up hill and it was fairly hot but i could hold my hand on it easy enough, so not scalding hot. hypoid diff's by there nature will generate heat

That is a good point, and is something the ARB instructions mention.

Think i will have to have another look at the ARB instructions and try and work out if mine needs grinding. I just presumed that as neither my front one, or old rear one had needed grinding, then this one wouldnt.

Is yours a 70 aswell?

 

[ModelMakerMan]

A couple of things to check before you go grinding the pinion: Compare the pinion from the old diff, is it any different in shape? Check the pinion preload. If the preload is wrong or the bearings are duff the pinion could be able to move in and out slightly, especially if the crush sleeve has been overtightened and backed off.

 

[Graham]

How about deliberately increasing the backlash, and reducing the pre-load by a small factor?
How accurate is the dial gauge?

Not made in China is it


Gra.

 

[Ben]

A couple of things to check before you go grinding the pinion: Compare the pinion from the old diff, is it any different in shape? Check the pinion preload. If the preload is wrong or the bearings are duff the pinion could be able to move in and out slightly, especially if the crush sleeve has been overtightened and backed off.

excellent advice Dave, thanks.

Going to have a look this morning before work.

How about deliberately increasing the backlash, and reducing the pre-load by a small factor?

I dont really understand what that would achieve?

How accurate is the dial gauge?

Not made in China is it


Gra.

of course! where else would it be made?

 

[Graham]

How about deliberately increasing the backlash, and reducing the pre-load by a small factor?

I dont really understand what that would achieve?

Gra.

of course! where else would it be made? [/quote]
.
Just the feeling that there is tightness there some where.
And if you rebuilt it all, without finding what you had done wrong, if any thing, then there could be a mis alignment some where.?
I think a fraction too much back lash would be more acceptable than too little back lash, as if the teeth of pinion gear is being forced too far into the teeth of teh crown wheel?

Where are the straws when I need them,,,


Hope you find some thing, if any thing,,, but the scolloped marks you imaged do seem to look like some thing isn't square, or is bent?



Gra.

 

[Scott]

Ben - fair play to you for having a go at this diff work, it looks like you've given it a dam good go.

Now I don't know a lot about building diffs up, but isn't there a step where you check the mesh of the pinion gear and crown wheel teeth using engineering blue? I'm sure I've seen some engineering blue smeared onto a few of the crown wheel teeth and then the diff being turned, the marks/inprint in the engineering blue show how the pinion gear is meshing with the crown wheel gear. I have seen a guide showing what the imprint in the blue should and shouldn't look like.

I don't know if the diff will get excessively hot like yours if the gears are not meshing correctly, but I suspect there may be some heat build up if they are not inline.

Google may be your friend for more detailed info. Hope that is of some help.

 

[ModelMakerMan]

Scot you only need to do that if you are setting up the pinion pre-load ie. youver replaced the bearings and are using a solid spacer or setting up with a crush sleeve. As Ben hasnt touched the pinion bearings he shouldnt need to do this but as I said above it looks like something may be out regarding the pinion in which case he might then need to.

 

[jeepmadmike]

Ben

On all the diffs I have ever build I have used a DTI to check the back lash but to be honest you can get it right enough just by feel... Usually back lash being excessive makes for noise and more noticeable "slop" on overrun to tight usually makes for noise and excessive wear and I expect heat

The bearing pre load I was and I think others where thinking about was on the diff carrier, the ones which the outers are moved by the adjustment collars

How did you turn them and how tight did you get them? This will not effect back lash as much but could cause issues as the components heat up. There is usually a torque figure for the collars and it's low low.

Your like me and have a go at doing stuff people think is a black art so it might take a bit of a fiddle- shame it means pulling the diff out each time....

Thinking about it all again- to late now too, but did you turn it by hand when it was hot?

And finally I would be very surprised it the crown wheel is on the piss - you did bolt it up in a diagonal sequence didn't you? I'm sure the book will have had that in it? If it is on the piss the mesh pattern will be out and the teeth will have witness marks on them. I expect it would be a noisy as a chavs corsa too