Diff Howl On Overrun

[Jamsey]

Ill start with some background information.

the car is a BA non xr ute (I know its an xr6t forum, but I thought I would ask for help anyway)

a year or two ago I grabed some 3.45 gears and bought a reco'd lsd and rebuilt the diff. it was all excellently put together if I say so myself and worked great.

it later became the burnout car when I bought my 1st xr6t. the lsd worked ok for abit but spun singles quite quickly. so I got another diff housing and built a mini spooled 4.11 diff. the diff lasted for ages doing burnouts and loving every second of it (the auto didnt love it much though :( ) until I bought a new auto and decided to wreck the old one by doing D bombs. and the diff stripped most of its teeth off with a spectacular BANG. many LOLS were had.

so to get a diff working I just chucked the mini spool centre into the 3.45 diff that had the lsd in it.

I was surprised that it worked so well without re measuring anything. so that diff lasted for the rest of the cars life as a burnout car.

then I bought a newer xr6t and decided the first xr6t would become the new burnout car (recycling cars) and the old ute can have a rest.

I then decided its time to sell the ute as it wasnt being driven much at all. so I scored a non lsd diff out of a vn calais, and agan just swapped the centres, this centre fit in a little too easy and had a bit of backlash. this ( surprisingly) ended up working really well. no noises or anything. this lasted about a week and a half (drove maybe 150km)

then one day I drove it up to get fuel as I had it advertised in the paper and it now howled when I backed off the accelerator, only above 40km/h though.

the first thing I did was chuck half a bottle of that moreys oil stabilizer in

but it didnt work.

so what causes noise on overrun? shallow pinion depth ( or atleast that's what trade school taught me).

my theory was that maybe since its a tad bit loose in the diff that maybe when I first put it together the crown gear sat properly on the pinion gear and the gears meshed up properly. but since theres that slight movement left to right in the diff the centre had moved away from the pinion enough to create this howl.

so I went in with high hopes. I drained the oil

took off the cover

and took off the end cap brace things.

and this is what I saw

I thought, yep! theres the problem. and tapped it back into place, and also tapped th eother side down which had also risen a bit. then I chucked it all back together.

and the gears look to sit on eachother fine

when I chucked the end cap things on I noticed they didnt cover the actual shim. I cant remember if it should or not. I assume it should, but it doesnt. whats the go with this? are they meant to support the shim (it makes sense that it would)

heres how it sits

I added some of that oil stabilizer in the oil again just finish off the bottle. and took it for a test drive.

I took it up to 60 and all was good. no noise when I coasted at all. then to 80 and coasted, and at first there was no noise, but then the noise came back, definately not as loud, but it was still there, and u cant not hear it.

so it didnt work.

would anyone have any ideas of what else I can try? I was told to chuck some sawdust in there just so I can sell it. but that's kinda dodgy, and I dont want to be that guy. im pretty confident the diff isnt going to crap itself any time soon, and im confident the car will be reliable for the next owner. but the noise is not an attractive feature, and would be much preffered not there.

so any ideas of what could be done? or if I may have missed something, or did something wrong. anything input at all would be great

and sorry for the long post.

[ratter]

Any time a diff is pulled apart, it needs to be checked, did you at least check tooth contact?

Did you keep the crown wheel and pinion matched as a pair?

Did you set the pinion depth and bearing preload if you did replace it?

Did you collapse the collapsible spacer?

Did you set side clearance and preload?

[Jamsey]

I checked tooth contact when I put the mini spool centre in and it was spot on. ill recheck it for this centre.

yes the gears were always kept as a matching set and were the original gearset used when I set all preloads and depth etc and when I did this I collapsed the spacer and set clearance and preload, this was set up 100% with the lsd centre, and whenever I changed carriers (mini spool, then open) I always kept the 3.45 gearset.

[ratter]

So it still has the original shims, even with the different centres?

If so that may be your problem, but should show up with either tooth contact test or back lash.

The bearing caps do not hold the shims in place, the preload from the diff case holds them in place, they should not be loose when fitting

[Jamsey]

they are still difficult to get in, but obviously not tight fitting enough if they have the ability to move.

ill do a tooth contact test during the week. when I put the mini spooled centre in there was no porblems. im guessing that's because the lsd centre and the mini spool centre both used bearing rebuild kits that I bought. the open centre one has never been rebuilt, and therefore is using the bearings from the manufacturer, which is apparently slightly different to ones u buy in rebuild kits today.

would it be worth opening this diff up again and try and see if I can push the centre towards the pinion by using like a screwdriver to try lever some movement in, and make enough space to fit a tiny shim, or just a thin piece of metal in there to try hold it in place? I bet I could jam a paper clip between the shim and housing

[ratter]

You need to use shims based on backlash and tooth contact, not based on a different bearing, the shim also helps keep the bearing cap square, so do not use something like a paper clip to hold it in place, you may need to purchase the right ship from a diff shop

[Jamsey]

thanks for your help ratter. ill see if I can get a shim from somewhere. theres only 2 places here in darwin that said they do diffs. and one lace said they wont do a ratio change for me as its too much trouble with the "machining" and the other place quoted 1800$ to do what I did with the 4.11's. that's the only reason I did it myself, I didnt really trust I had done enough of them to try a full ratio change with all new measurements and setup. but I have a bit more confidence in them.

[ratter]

Good luck with it mate, it is critical to have everything 100% otherwise you do end up with noises etc

[F1PERFORMANCE]

my tip would be to put more preload on the pinion if it spins easy 9 out 10 times more preload will fix it.