LSD Questions....

[RichardDN]

Hi Guys First time poster: So just fitted a LSD in the rear of my 97 bighorn not done much testing yet. but what i did notice when in Hi or lo 4wd and making a sharp slow turn (this is on pavement) the inside wheel nearly locks up cant really do a u turn if i take it out of 4WD its normal can make turns no problem is this normal? i'm using 80-140 syn and no extra additive. Cheers for any info

[geeves]

DO NOT DRIVE ON A HARD SURFACE IN 4WD
Its not your lsd causing this.
I will assume that in 4wd you either have a sotf front diff, auto hubs, or manual hubs in the locked position. The transfer case is a solid connection between front and back wheels so front and back must travel at the same speed. But in a corner the front wheels go further than the back wheels so must go faster. This cant happen so something has to slip. It can also do terminal damage to the gearbox although Ive never seen this happen on an Isuzu I have seen it on a mazda

[RichardDN]

Thank you for your reply Geeves, ok so that grabbing is normal then thats a relief i only did it for a few minutes when testing i aways drive in 2wd im not a 100 percent sure of front diff its open i guess with auto hubs not TOD standed auto.

[geeves]

You will have one of 3 things in the center of your front wheel.
Most likely is a solid plate with a bump in the middle This is a drive plate and the free wheel function it handled by a dog clutch on the side of the diff. As soon as you select 4wd the gearbox tells this clutch to lock
Second choice is a large hub with auto written on the side. t5his is an auto hub. They are fine for casual 4wding but on serrious stuff they have a habit of unlocking when you change from forwards to reverse etc Just what you want on a failed hill climb with everything about to go wheels up is 2wd.
Third choice is a large hub with a knob in the center This is the manual hub Works as well as the first option and has the flexibility of allowing you to select low4 but not lock the hubs giving low2 in effect. If you are as good as I am backing trailers then being able to go extra slow is an advantage.

[RichardDN]

Cheers, pretty shocking backing trailers if doing it for a day i usually get the hang of it just as im on my last trip lol, thinking of putting some 40mm raised springs in the back and winding the front up, but do i wind it 40mm or 35mm or something else? will it make it harder ride in the front i'm not to keen on a bumpy ride at all thats why I'm putting in rancho 9000 shocks and setting them on the softer side for daily driving i heard setting 5 for front and 4 or 3 for back, i'm not a speeder if its going to be a harder ride with raised front will just get standed height springs.

[geeves]

50mm raised rear springs and raise the front to match will be fine

[gomulletgo]

By: damo667 "diff in my 1990 2.8td ubs55 bighorn ........ started to crunch climbing and cornering at slow speeds, especially from stationary.......
probably shouldn't be driving, it sounds like its missing a couple of teeth already......"

That sounds like the EXACT same vehicle and problem as I am having, see thread here: http://www.clubisuzu.com/viewtopic.php?f=25&t=2859
(REAR DIFF NOISE, CLUNKING, THUMP THUMP THUMP )

Have you found a solution to this issue yet? Have you replaced the diff and did it fix it? I see you've replaced the driveshaft center bearing and that didn't fix it, bugger, my center bearing is shot too and I hoped it may be a cause rather than a symptom.

I look forward to hearing from you damo or anyone who know's the solution to this issue, as far as I can see 3 members on this forum at least have/have had this thumping diff in the same way.

Cheers guys

[geeves]

Center bearing on my bighorn let go in Stratford a few years back. Driving back to Wellington with a driveshaft that wanted to follow the outside of the bearing housing causing the whole car to lurch and jump off the ground at speeds under 40kph was not fun. On the 2.8 there is nothing you can do as the transfer case will pump its oil out while driving with the driveshaft removed.

[isuzurob]

i know damo replaced his diff head when i caught up with him down there

[gomulletgo]

i know damo replaced his diff head when i caught up with him down there

Ok, good to know. Do you know if that solved the issue for him?

Center bearing on my bighorn let go in Stratford a few years back. Driving back to Wellington with a driveshaft that wanted to follow the outside of the bearing housing causing the whole car to lurch and jump off the ground at speeds under 40kph was not fun. On the 2.8 there is nothing you can do as the transfer case will pump its oil out while driving with the driveshaft removed.

That doesn't sound fun mate. I'm quite amazed how my isuzu has just kept on trucking this long with this issue, but it's in serious need of help now.

[geeves]

It had a slight vibration for a while but when it let go it went suddenly. 2 days off road might not of helped

[topgun94]

Hey guys. Where are you getting the shims for the rear LSD?
I have a 1991 2.8 mu with an LSD. Are these doffs able to be shimmed?
Cheers in advance guys

[nb422]

We just used big washers and they worked fine

[isuzurob]

can get the shims from holden dealer or diff rebuild shops, or as above washers

[topgun94]

Anyone have the Holden part numbers? And thicker the shims tighter the diffs?

[isuzurob]

will try get a price and part numbers for you tomorrow, yes thicker the shim tighter the lsd, to tight and its a locker

[topgun94]

So i called holden today and they said shims are only like 10 bucks. Which is wonderful. Just wondering though what thickness i should go for and if any one has found a good write up on the project to have a read over before i start?

[isuzurob]

it doesnt take much and depends how tight you want it to be? just get thickest ones and machine them down till you are happy with the break away of the lsd

[Brinky]

Just pulled the lsd out of my 92 Mu with the intention of adding some shims to both clutch packs. The spring pressure is created by two dish spring washers each side so a thin shim will make quite a difference to the preload. Should I try one 0.8mm shim per side or better to add 1mm per side? I could turn the LH wheel quite easy with the RH wheel on the ground and car in neutral allowing the drive shaft to spin. I don't want to end up with a locked diff, but want to make a difference. I don't want to pull the diff out again if I can help it. Thanks.

[Brinky]

I worked out if you put a wheel flat on the garage floor inside facing up, place the axle into the wheel, put the lsd hub onto the bottom axle, insert the other axle in the lsd hub, then use a bar the same length as the wheel diameter, you can test the break away load of the lsd. Even better is set up the torque wrench to turn the top axle while you are standing on the bottom wheel. I was only getting 40ft/lbs without a shim. Adding a 0.5mm shim increased the break away load to 80ft/lbs which I'm happy with. As isuzurob says, it doesn't take much and after measuring the clearance in the hub I think more than 0.5mm might make the lsd into a lock hub. Now to put it all together again and see how much diff oil I can spill onto the garage floor. I'm good at that.