Rear differential pinion seal replacement.

[claybodie]

Hi,
I was wondering if the pinion seal for the rear differential is removable without the 'special tool' found in the shop manual. Does anyone know if this is available at Autozone?
Disclaimer: novice mechanic.

My differential is leaking a pretty decent amount of gear oil and I was hoping a new seal would help. Has anyone had success with that?

Thanks,
Clayton

[asavage]

This one will require an air impact wrench. The pinion's companion flange nut is on very tight, and needs to be put back on very tight as well. You don't have to have the companion flange holding tool, though you can build one from a 3'-4' length of 1.5" angle iron -- I've done it in the past.

This job also requires a jaw-type puller to remove the companion flange.

PINION NUT torque: 94-217 ft-lb

[claybodie]

I have a question about removing/replacing the pinion's companion flange bolt -
It says in the manual that the preload torque (w/ oil seal) should be 1.1-1.6 N•m (11-16 kg-cm, 9.5-13.9 in-lb). This doesn’t seem like much, considering that the torque wrench measures in kg-m (ft-lb). I understand that over-tightening the pinion bolt can cause some kind of internal collapsible spacer to be irreversibly crushed.
Does anyone have a comment on this? Is there any reason for concern as long as I carefully re-tighten the bolt after replacing the pinion seal?

Additionally, it shows in the shop manual the use of hand tools to tighten the bolt - is there any reason why I wouldn't be able to create the required torque to get it back on (because I don't have an impact wrench).

Thanks,
Clayton

[asavage]

It says in the manual that the preload torque (w/ oil seal) should be 1.1-1.6 N•m (11-16 kg-cm, 9.5-13.9 in-lb). This doesn’t seem like much, considering that the torque wrench measures in kg-m (ft-lb).

It's not very much. In fact, it's very little. But too much pinion bearings preload has major implications on the life of those bearings. However . . .

I understand that over-tightening the pinion bolt can cause some kind of internal collapsible spacer to be irreversibly crushed.

It takes a lot of torque on the pinion nut to crush the collapsible spacer.

Is there any reason for concern as long as I carefully re-tighten the bolt after replacing the pinion seal?

Additionally, it shows in the shop manual the use of hand tools to tighten the bolt - is there any reason why I wouldn't be able to create the required torque to get it back on (because I don't have an impact wrench).

Let me pose a Q: have you ever tried to hand-torque to 200+ ft/lbs? It's not as easy as it sounds.

Overtightening the pinion nut (and further crushing the spacer) isn't usually a problem, because you can't get near enough torque on the nut -- at least, most people can't.

Measuring the pinion brg preload can be done using a light spring scale and a short radius extension -- I've got an inch-pound torque wrench, but I wouldn't use it at low of a spec, it's not accurate enough. But I wouldn't bother measuring bearing preload at all, unless you're replacing the pinion brgs. Which I do not recommend.

Oh: use some sealant under the nut when reassembling. Gear oil can creep up the splines.

[davehoos]

pinion flange seal.
common practice is to mark the nut,pinion and flange.
replace seal,refit flange,then tighten nut to the original possition ignoring tension.if the nuts in the same possition everything should be home.

its easy to colapse spacer,destroy bearings and upset alignment.often on road test you can hear the bearngs reseating.if you can hop the vehicle at low speed then recheck preloads.if there is movement oil will leak out of the spline.

"that the preload torque (w/ oil seal) should be 1.1-1.6 N•m (11-16 kg-cm, 9.5-13.9 in-lb)"
this preload is measured wih crown wheel removed.
for onvehicle repairs with the axle on stands,drive shaft and brakes removed[pads or drum].measur tourque required to turn pinion.

R31 skyline has borgwarner 78 series rear axle,similar to many other vehicles.the pinion is positioned using the crush spacer,in normall use the flange moves on the spline,not good.
when these diff is repaired the crush spacer is replace with a solid piece of tube and shims.

[claybodie]

Thanks for the info.

At this point it seems unlikely that I will be able create enough torque to get the bolt off.
I am also working on replacing the center bearing (see that feed). I managed to un-stake the nut but I'll be damned if I can get that nut off the center bearing. I torqued on it so hard I bent a piece of unistrut and two bolts out of which I had fabricated a 'special tool.'
I imagine the pinion flange seal nut will be as difficult.

So I may save this job for the pros, or at least someone with an impact wrench.

Have any of you actually done this without an impact wrench? Could you give me more information on the tool you used to stabilize the pinion flange?

Clayton

[asavage]

A few years ago when I was helping a friend in a remote town do a similar job, I rented an air impact wrench from a typical rental yard. It cost me $15 for the whole day. I had access to an air compressor though.

I haven't seen an electric impact wrench that develops enough torque to do that job -- though I bought an IR electric impact wrench in 1977 and still own it, it's only useful for very light jobs.

[redmondjp]

. . . Have any of you actually done this without an impact wrench? Could you give me more information on the tool you used to stabilize the pinion flange?

Clayton

It can be done, but you will need something beefier than the unistrut. I did this on a '73 3/4T Chevy truck rear end w/o an impact wrench--I borrowed a flange-holder tool (cast steel) from the high school auto shop where I used to go which bolted to the yoke, and then put a cheater pipe on that which contacted the ground to prevent it from rotating. Then I used a 3/4" inch drive breaker bar with a long cheater pipe on it, and I think it stuck out the side of the vehicle just far enough that I was able to jump on it (3/4T truck is raised up high enough that there was clearance out the side to do this). This nut was torqued to 275 lb-ft of torque.

Get yourself some 1/4" thick angle iron with 2" wide flanges on it and bolt it to the yoke (it's a lot of work--may require some relief cutting to allow the socket access to the nut). But here's an idea which may also work--find a 18" or 24" pipe wrench and put that on the yoke, and then put a cheater pipe on the handle of the pipe wrench.

Of course, you have already applied a penetrating oil to the nut such as Kroil, PB-Blaster, or Liquid Wrench, right?

[asavage]

pinion flange seal.
common practice is to mark the nut,pinion and flange.
replace seal,refit flange,then tighten nut to the original possition ignoring tension.if the nuts in the same possition everything should be home.

Good advice!

its easy to colapse spacer,destroy bearings and upset alignment.

This has not been my experience, but I have never had to do this job on a Nissan -- ever -- so I'm willing to learn.

often on road test you can hear the bearngs reseating.

Ouch! I never want to hear roller bearings "seat". Today's ball and roller brgs do not require any "bed-in".

this preload is measured wih crown wheel removed.

Thanks for clarifying that -- I forgot to mention it. Clayton, you can't measure the pinion brg preload on an assembled diff, the ring gear ("crownwheel") brgs plus the hypoid sliding friction will add considerable drag, throwing off such a low spec measurement.

R31 skyline has borgwarner 78 series rear axle,similar to many other vehicles.the pinion is positioned using the crush spacer,in normall use the flange moves on the spline,not good.
when these diff is repaired the crush spacer is replace with a solid piece of tube and shims.

Aha! So they went back to the tried-n-true preload adjustment method. Harder to set up, but remains perfect after assembly.

[claybodie]

All good advice, thanks everyone.

I think I may be able to secure an impact wrench and air from a friend, so I may not have to manufacture the setup mentioned above. Although I think I would pay money to see someone jumping on a piece of pipe sticking out the side of a vehicle...

So what about securing the smaller propeller shaft that's been removed from the vehicle (for replacing the center bearing)? This will be the first time I've used an impact wrench.



Clayton

[claybodie]

I also have not applied a penetrating oil. That sounds like a good idea.

[asavage]

So what about securing the smaller propeller shaft that's been removed from the vehicle (for replacing the center bearing)? This will be the first time I've used an impact wrench.

While you are reasonably safe using an impact wrench to remove fasteners, without damaging anything, it's disturbingly easy to break things when tightening with one.

A major problem is that every impact wrench has different torque than any other one, and all are affected significantly by line pressure and hose length. In practice, you use one wrench and one air supply setup, and get "used" to how long to hold the trigger on to get the desired torque. In the shop, if you borrow your mate's wrench, you get surprised at the different results you get. I've had it happen to me.

Fortunately for you, you are working with two very tough-to-screw-up assemblies. Unless you borrow a Snap-On 600 ft/lb 3/4" drive air impact, or you run 150 PSI line pressure, you pretty much can bet that holding the gun at max for six to ten seconds is going to be fine (for the carrier brg). The pinion brg is a tougher call, based on Dave's input. If Dave hadn't said anything, I'd be rattling for a full ten seconds on that nut, for tightening. Plus locktite Red.

As to the pipe on 3/4" drive socket under the truck: this is exactly the way we've done Chev etc. pinion brg nuts. The bar I hang on (truck on a lift) is about 5' long, and I really hang on it. The nut can't be tightened effectively otherwise. But that's bigger iron than the Datsun.

I don't like to use a pipe wrench on the companion flange or yoke because of the damage it does.

[claybodie]

One of the manuals I have says that to replace the pinion seal, the differential case assembly should be removed, the drive pinion should be removed, and the collapsible spacer should be replaced.

I understand that it would be useful to replace the seal behind the differential case assembly and the collapsible spacer, but I don't want to get in over my head.

It seems like from what everyone says the pinion seal can be replaced without removing the drive pinion or the differential case assembly.

[davehoos]

Better to replace the seal than:
1) run out of oil
2) have oil mess all over the rear end.

But when working on differential you should treat it as a rebuild. Most of the time you can get away with it.

Now back to reality. Regarding the collapsible spacer, this is a single use item. When reusing one, it is common practice to add 2 or 20 thou shim[memory fading]. The spacer has tension built in to hold the bearing apart and once crushed your dealing with unknowns.

Not really explained to me but there are only a few axle makers in the world, and others are copies or under liecence. Japanese diffs probably come off the same assembley line. I've worked on heaps of Trooper diffs and they look the same as the Nissan Banjo diffs. Mostly the Limited Slip Diffs have fallen apart, or the pinion nut fell off. The big drama here is how long they had been driven without oil or how much metal is inside. About a week after the repair they get towed in.

I seized a diff in a Landrover during the quality control inspection road test. The diff had no oil and travelled about 6 miles!! It locked up as i got to 60 mile/hour.

[asavage]

One of the manuals I have says that to replace the pinion seal, the differential case assembly should be removed, the drive pinion should be removed, and the collapsible spacer should be replaced.

Due to the collapsible spacer design of pinion brg preload, accurate setting of preload is supposed to be done once per spacer, and that's why the factory manual says to replace the pinion spacer every time you touch the pinion nut.

However, almost nobody disassembles the diff to replace the pinion shaft seal. It's a LOT more work, and in practice, on an old diff, you do not need to be all that close on brg preload.

I understand that it would be useful to replace the seal behind the differential case assembly and the collapsible spacer . . .

There isn't an internal seal. The only "seal" other than the axle seals and pinion shaft seal, is the housing gasket. Even if it leaks, a much easier fix for a leak at that gasket is external application of sealant.

It seems like from what everyone says the pinion seal can be replaced without removing the drive pinion or the differential case assembly.

Correct. The touchy part is tightening the pinion nut tighly, but not so tightly that the collapsible spacer collapses further. Dave's suggestion to mark the relative position of the nut to the pinion shaft is a very good one. Use a pin punch or similar to make permanent marks. Don't rely upon marking the companion flange, its position can move relative to the pinion shaft (it's splined but not keyed).