to all the diff guru's out there

[SamLogan]

Hey guys,
A couple of months ago I was driving along the road not doing anything stupid and my rear diff gave way. The outer tips of the teeth on the crownwheel broke off and got pulled through the crownwheel and pinion. The diff was setup by a 4wd shop down here. Well it has happened again. Driving along the road and I started to hear a knock. Dropped the oil and a tooth tip came out. I cleaned the axle housing out last time as well. I am at a loss as to why it has happened. What causes the tips to break off?

Cheers
Sam

[sibainmud]

Too much or not enough mesh when shimmed up. Did they measure the backlash?
No guru, but set up heaps of stern-drives in boats and they sh!t themselves real quick if not set up right.

Cheers,

[muddyplumber]

Can't help ya but,shit bro that sucks

[slide]

Can you see wear pattern on teeth at all? I'm guessing it was a bit to new to see anything?
The load shouldn't be on the teeth ends, so I'm guessing either wrong setup, poor casting of gears, or foreign peices getting in there.
If could well be a combination, ie a weak crownwheel, setup wrong, fractured under load, then later picked up a small bit that had chipped off and went through the gears destructing them quickly.
Or, it wouldn't be you've backed into a rock and damaged the housing??
Hope that might help you in some way,
Nath

[pruggerdore]

what sort of truck and how much power you putting through it. poorly setup as already said. pull it out take to another diff expert get his assesment and then will probably end up argueing with the guy that set it up.

[SamLogan]

Yeah it has to be a setting up issue. Both times they were a factory set up diff that had only the carrier swapped over as I have a lockright. So both times it has only been the backlash that has had to be reset as the pinion depth was kept the same. I haven't taken it out yet but the last one had no unusual wear patterns on the crownwheel. It is in a surf with a 1kz with mechanical pump with a bigger turbo. Wouldn't be anymore that 160 hp. The engine has just been rebuilt as well. I am running 35's which really isn't that big for them.

Cheers
Sam

[rangimotors]

What's your suspension set up ? I've seen that happen to lots of guys with lots of flex in leafs but no tramp bar so I guess what I'm asking is is it possible your housing is twisting so u get a terrible pinion angle and things don't mesh as they should ?

[tweake]

Yeah it has to be a setting up issue. Both times they were a factory set up diff that had only the carrier swapped over as I have a lockright.

so you used a 2nd hand diff for the rebuild after the first one stuffed out?

they don't really even need to check the backlash when fitting the lockrights as it doesn't change if everything is the same.
however if they put everything back exactly the same the bearing preload could have been loose. big power on them can cause the ring gear to shift over a bit which changes how the teeth mesh.

more than likely whats happened is the guys never setup the diffs in the first place, they chucked the locker in and left them as stock.

put some decent aftermarket gears in this time.

[SamLogan]

its a 3link rear end so there is no issue with that. I set the diff up with the mechanic at my mates work and Turoa checked it the second time. I am thinking maybe the preload may not have been enough even though I made sure it was pretty tight. It just seems strange it knocked the tips off. I would have thought something like that may have been due to incorrect pinion depth causing point loading on the tips. Will put some photos up of it when i take it out. The first one lasted a year. This current one lasted only about 1 month. Would having too little backlash cause problems as Turoa said he runs his ones tight.

Sam

[tweake]

now the truth

i assume you didn't pull the pinion out when you did the locker. so it shouldn't be pinion the ring setup, unless you failed to fit the adjusters back to their original positions. if one side is tightened up more then the other it will shift the ring gear sideways and yes it can cause loading on the tips of the gears.
you don't want backlash to tight either. do you remember what it was set at?

my carrier bearing preload was fairly soft, about 80 ftlb i think, so i cranked it up two notches a side which put it up to ~120 ftlb. for a high powered engine i would have gone up to 150 ftlb.

[SamLogan]

yeah i forgot to put that bit in. The adjusters etc were put back in the same side and it was adjusted so the backlash was less than 1mm. Tu's checked it and said it was fine. Slightly on the loose side for a 4wd but good enough. Does putting the adjusters back in to the same spot matter if you are going to be adjusting it anyways to the correct backlash? The pinion was never touched as it was a straight carrier swap.

Cheers
Sam

[Sadam_Husain]

Well it has happened again. Driving along the road and I started to hear a knock. Dropped the oil and a tooth tip came out.

you might want to consider the bad luck factor as well if its been set up properly and checked over.... it hardly sounds like you were doing anything that was capable of ripping a few teeth off

[suzolla]

Hi,
1mm backlash is way too much, should only be about 0.2 to 0.3mm, large backlash will put the load nearer the tips of the teeth.
When you pull it out before you strip it you should recheck the backlash and also do a check to see where it is contacting to help understand why it may have failed.
Cheers
Tim

[wopass]

Hi,
1mm backlash is way too much, should only be about 0.2 to 0.3mm, large backlash will put the load nearer the tips of the teeth.
When you pull it out before you strip it you should recheck the backlash and also do a check to see where it is contacting to help understand why it may have failed.
Cheers
Tim

what are you doin up at this time of the morning mate?? are you doing home night shift in sympathy for us here on the Gen??


smoko!!

[kbjj]

After rooting 2 high pinion gears, I fitted a "Precision Gear" gear set, and spent a couple of hours fileing diff housing flange to match fit elocker (used paint as a type of bearing blue) I never checked this face after all the welding . Then straightened housing as was slightly bent. Has lasted so far, although I hav'nt done enough k's to be convinced, but I'm quitely confident.
Not sure if this helps , or just adds to the confusion. Either way I know it sucks a big fat one.
Good luck
Jeremy

[hosehustler]

I buggered a few as well, most second hand ones already have plenty of years and K's on them.
I'd go with the advice on fitting a new gear set, I never had any trouble with mine after that.

[SamLogan]

Mine was tighter than 1mm. Tu's had a feel and said that it was good so we left it at that. I took his word for it has he has set a few up and i know how he drives his trucks and they don't break with all the abuse. My problem is buy the time you buy a new ring and pinion and new bearing set etc and then pay someone to set it up like the warranty for a lot of ring and pinions want, you are looking at close to 1000 dollars. Looks like i will be driving around in front wheel drive for a while. I might buy one more secondhand one and get it cryod and then save up. If I am going to be buying a new ring and pinion i will buy a 4.5 which means i have to get a hi pinion 4.5 for the front as well.

When i pull it out i will let you guys know what i found.

Cheers
Sam

[kbushnz]

I got my last r and p in from the states.. Landed it was only a bit over $350 NZD..
Then another few hundy at my local diff man....
Cheapest option...
The local r and p re sellers were asking over $800 for a new set....
And getting from Aussie was more !

[Lawrence]

I don't think you can get a 4.5 high pinion.

[SamLogan]

Yeah i will have to look into it. I am not wanting to do another one. It is a pain in the ass.

you can get 4.5 ones out of the states.

Sam

[SMOKEY]

Are you still running a collapsible spacer on the pinion ??, if so in my opinion big tyres and a heavy jandal especially in reverse = broken diff .

33" TYRES MAX , or lighter JANDALS,

FITZY.

[rokhound]

Are you still running a collapsible spacer on the pinion ??, if so in my opinion big tyres and a heavy jandal especially in reverse = broken diff .

33" TYRES MAX , or lighter JANDALS,

FITZY.

Or ditch the stupid collapasable spacer and fit a solid one.

(33" boots, jeez Fitzy, you are sounding like a scuzzyduck )

[Bulletproof]

You say you only replaced the carrier.

Did you check the pinion preload ? Because if it is too loose it could destroy Crown

Did You Screw the the Carrier shims up tight on the bearings first before you made the adjustment sideways for the the correct Backlash and preload. Sometimes you think they are tight and they are just stuck.

Did you Blue the the teeth because on a worn Ring and Pinion what the workshop manual says is not quite correct for good markings. The important marks are halfway up the teeth as opposed to the forward and back.

For road use I usually go for 3 notchs of preload instead of the 1 1/5 the books says and 5-7 thou back lash.

Cheers Richard

[tweake]

yeah i forgot to put that bit in. The adjusters etc were put back in the same side and it was adjusted so the backlash was less than 1mm. Tu's checked it and said it was fine. Slightly on the loose side for a 4wd but good enough. Does putting the adjusters back in to the same spot matter if you are going to be adjusting it anyways to the correct backlash? The pinion was never touched as it was a straight carrier swap.

Cheers
Sam

you can do it by back lash but you have to measure the existing backlash (measure not guess!) and then put it back to the exact same backlash.
if backlash was looser than stock then the gears would be apart a bit more and driving off the tips more.
marking the adjusters is easier as most people don't have dial gauges at home.

For road use I usually go for 3 notchs of preload instead of the 1 1/5 the books says and 5-7 thou back lash.

bugger the notches get the torque wrench out.
tho from what i found with mine i think 3 notches on a good diff will be right in the ball park. but for highpower with big tires i would go more again.

[Bulletproof]

For road use I would not go too tight on the preload. I know others are running about 5 notchs and for trailer queens and trial trucks this is fine because they don't have time to build up heat.

The Tundra 8 inch diff have a gusset across the back to hold the 2 sides of the carrier from expanding and in the USA they are running huge V8s and big tyres without a problem. .

I experimented with the preloads and basically for every extra notch of preload the bearing goes out of line by about 1 thou. So 5 notches means the bearings are out of true by 5 thou which is not good for 100kph without damage happening.

Cheers Richard

[SamLogan]

Yeah i just swapped the carrier over. We made sure we tightened the adjusters first and then set the backlash. I think we set the preload as about 3 notches. I have just been to pick a part in chch and managed to find a 4.3 diff in a hiace van that i got for $30. Bearings etc all look fine. I am going to pop that in and then worry about the locker some other time. i will get Rick to set it up as apparently he is quite good at it. Thanks for the advice guys. Lesson learnt. I have a feeling maybe the backlash was a bit too loose for the power and big tyres. About to go swap it over so i will let you guys know the findings.

Cheers
Sam

[tweake]

I experimented with the preloads and basically for every extra notch of preload the bearing goes out of line by about 1 thou. So 5 notches means the bearings are out of true by 5 thou which is not good for 100kph without damage happening.

Cheers Richard

how much torque was applied to the adjusters to get it up to 5 notches?

[Bulletproof]

I experimented with the preloads and basically for every extra notch of preload the bearing goes out of line by about 1 thou. So 5 notches means the bearings are out of true by 5 thou which is not good for 100kph without damage happening.

Cheers Richard

how much torque was applied to the adjusters to get it up to 5 notches?

I can't remember exactly because it was a long time ago but I think it was around 150 foot lbs.

If I was going to run big power with big tyres I would import a Tundra diff nugget and then modify the back of the diff housing. That way you have a small 8inch that is strong

You can just see the strengthening gusset in this picture of the tundra diff



Andrew Thomason who lived next door was running Tundra diffs in his offroader with no trouble

Cheers Richard

[tweake]

i was just trying to find where i read it.
i think 150 ftlb is at the max of Toyota's specs but not over it.

[Bulletproof]

One other thing. Did you mark your bearing caps before you removed them with a punch.

In the factory the thread is done while they are bolted together so if they end up on the wrong side it may appear to tight when in fact it isn't and it will also put uneven pressure on the bearing.

Cheers Richard