rear diff oil leak....a few answers please???

[andycook]

Noticed oil on bottom of rear diff, then some on fuel tank above prop, and underside of rear diff, it looks like its coming from around the front of the rear diff where the flange is that joins with propshaft.
did a quick search and found others have had this problem

I recently installed extended diff breather, with new breather, which hasnt sezied

3 questions
1) what is the part name for the oil seal I need, and where can I get it cheaply?

2) is it an easy job to change the seal? and what about this pinion backlash business...

3) I have a LSD rear diff, but the LSD is buggered, and truck has done 150 k MILES. Is there any point in putting special LSD oil in it if it doesnt work anyway, or can I just bung in normal gear oil? and if so what type?
I put LSD oil in last year when i chanegd the oil and LSD still didnt work

thanks
Andy

[TonyN]

1/ its just the oil seal for the companion flange or pinion.

2/ its easy to change, the trouble comes with the pinion backlash like you said, the correct way is to remove the seal, then pull the bearing (probably special tools needed, the manual list one, and I havn't tried to get one out yet) and the crush sleeve which sets the pinion backlash, 9 times out of 10 you can just change the seal and bolt the pinion back on and call it good. But you should check the preload to do it properly, if your preload is less than spec (16-22.6 in/lb new, 7.8-11.3 used bearing), and you cant torque the pinion up any more (253 ft/lb is the max) you need to replace the crush sleeve and start again.

The seal needs to be 1mm under the end of the diff housing.

Check the nut fist, it comes undone quite frequently and then the pinion is loose and it leaks.

Its the sort of job that every man and his dog will just change the seal and bolt the pinion back up, but every now and then the crush sleeve will be squashed to much and the pinion will be to baggy.

3/ Dunno, I'd still put LSD oil in it, just in case as all the clutch packs are still in there rubbing against each other.

Hope this makes some sort of sence, have just got back from the local!

Noticed oil on bottom of rear diff, then some on fuel tank above prop, and underside of rear diff, it looks like its coming from around the front of the rear diff where the flange is that joins with propshaft.
did a quick search and found others have had this problem

I recently installed extended diff breather, with new breather, which hasnt sezied

3 questions
1) what is the part name for the oil seal I need, and where can I get it cheaply?

2) is it an easy job to change the seal? and what about this pinion backlash business...

3) I have a LSD rear diff, but the LSD is buggered, and truck has done 150 k MILES. Is there any point in putting special LSD oil in it if it doesnt work anyway, or can I just bung in normal gear oil? and if so what type?
I put LSD oil in last year when i chanegd the oil and LSD still didnt work

thanks
Andy

[Delboy]

Just remove the prop shaft from the flange after marking both for reassembly in the same orientation, then;
1. Drain diff oil
2. Undo bolt taking note of how may threads are showing above it for reassembly(you will need a bar bolted into the flange to hold it while you undo and do up the bolt.
3. Remove washer
4. Pull off flange
5. Remove old seal (might be a bit tricky having the pinion in there, but is possible)
6. Insert new seal with a little instant gasket on the outside edge and a little grease on the rubber to eliminate dry start off which can wreck the rubber on the seal. Like Tony said, the seal should site about 1mm below the edge. It is tapered, so dirve it to the bottom of the taper
7. Put flange back on
8. Put washer back on, then bolt with a little loctite
9. Tighten bolt back up until same amount of threads are showing. There should be a dimple in the bolt, that should line up with the notch in the pinion. Pull flange in and out. If there is any movement then it isnt tight enough. The only risk here is that it is overtightened in which case your bearings will wear out more quickly and thats a much bigger job!
10. Bolt prop shaft back on and off ya go!

Hopt that helps! Up to you whether you want to do it yourself or not!

1/ its just the oil seal for the companion flange or pinion.

2/ its easy to change, the trouble comes with the pinion backlash like you said, the correct way is to remove the seal, then pull the bearing (probably special tools needed, the manual list one, and I havn't tried to get one out yet) and the crush sleeve which sets the pinion backlash, 9 times out of 10 you can just change the seal and bolt the pinion back on and call it good. But you should check the preload to do it properly, if your preload is less than spec (16-22.6 in/lb new, 7.8-11.3 used bearing), and you cant torque the pinion up any more (253 ft/lb is the max) you need to replace the crush sleeve and start again.

The seal needs to be 1mm under the end of the diff housing.

Check the nut fist, it comes undone quite frequently and then the pinion is loose and it leaks.

Its the sort of job that every man and his dog will just change the seal and bolt the pinion back up, but every now and then the crush sleeve will be squashed to much and the pinion will be to baggy.

3/ Dunno, I'd still put LSD oil in it, just in case as all the clutch packs are still in there rubbing against each other.

Hope this makes some sort of sence, have just got back from the local!

[andycook]

thanks Tony & Delboy for your advice and detailed description of the job,
I think I will give it a go, need to get in touch with Roughtrax and get the seal,

cheers
Andy