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How bad will this be

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Stewart

Stewart

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I need to change the front seal on the rear axle 120-810. How much fun is the job going to be? Its still a very minor leak but its something I would like to nip in the bud before it gets worse of coarse being an MG one seal will more than likely lead to rebuilding the rear axle somehow.
 
Why would you want to fix that? The diff seal is the best source for under body rust protection there is! /ubbthreads/images/graemlins/wink.gif
 
It's likely you've already read the Bently version. If it were mine I'd plan on the rebuild, just due to the age of the unit. They are generally very stout and don't NEED the cup-washers , bearings etc. replaced BUT: to get the right pre-load on the pinion requires a new crush-tube, it's a "bench proceedure". Once ya open the unit up, may as well have a good look at everthing in there. Just my 2p.
 
Well, you'll proabably need a impact gun to remove the big nut on the driveshaft flange, then once the flange is is removed the seal will be exposed. Simply pry it out with a screwdriver. To install the new one, use a hammer and something flat like a a piece of metal, use a piece of flat metal as something to lay over the new seal so that when you strike the metal the seal gets drifted in all the way around and not damaged. It's a pretty straight forward job, your biggest pains will getting the big nut and flange off, after that it's no biggie.
 
Hap is right again, gesh. Nut off, seal out, seal in. Worth buying an impact wrench for the job, next time I will have one for sure.
 
True, but I think the "nut on" part can be a bit of a fiddle. I wouldn't just spin it on with an impact gun, use a torque wrench. I think it has a fairly high torque spec, like 150ish lb/ft. And if you squish the crush tube too much, you're in for some real fun.
 
Oh yes, impact wrench to remove not install.
 
So this is the procedure that Haynes, et al say should be done by the dealer?

While we're there, how difficult is it to replace the pinion bearings?

I recently procured a tube-type axle to convert from wire wheels to bolt-on and have been a little concerned with refurbing the bearings due to the doom-and-gloom in the manuals.
 
Mark the pinion nut in relation to the pinion gear and replace it in the exact position as removed. Otherwise you will change the preload. And from past experience , the pinion seal seldom leaks unless there is another problem. There should be no lost motion in the pinion flange. If it moves back and forth after tightening the pinion nut then something needs attention.

Alan T
 
Very seldom are the bearings in the differencial in need of replacement even after 40 years. I should think an exception might be raceing or running dry. They do run in an oil bath.
 
Yikes worse than I thought. Looks like its going to have to be sent to a pro as I dont have the skill to set up the internals of a diff.
 
I've been putting mine on with my ingersall impact wrench set on high for 20 years, never had a problems, if I've been doing it wrong, you sure could have fooled me /ubbthreads/images/graemlins/smile.gif If the seal continues to leak after the new one is installed look at a redi-sleeve to cure the problem. Like Jack said the diff are darn near indestructable, in 20+ years the ony one i managed to tear up up was with a 60mph down shift in a race car, spun the gears off the pinion, didn't even hurt the ring gear, these things are tough and last forever.
 
Got to disagree with Hap on this one, although how do you disagree with positive experiences? LOL

The preload collar/tube is all that maintains the pinion depth and if you overload it you are supposed to be condemned to differential purgatory. :smile:

I have never done the impact wrench thing. Instead I do as Alan says, and how they taught us at BMC classes, marking the nut and end of the pinion shaft and then removing the nut with great care, counting each revolution so that it can be reinstalled in the exact same position.

Jack
 
Well everybody may be correct. If you happen to have an impact air wrench with a calibrated clutch adjustment you can set the breakaway torque on it. If it is not so equipped very few Impact wrenches will exceed about 140Lb/Ft of torque. So use which ever method you are equipped to handle and feel comfortable with.---Fwiw--Keoke
 
[ QUOTE ]
Well everybody may be correct. If you happen to have an impact air wrench with a calibrated clutch adjustment you can set the breakaway torque on it. If it is not so equipped very few Impact wrenches will exceed about 140Lb/Ft of torque. So use which ever method you are equipped to handle and feel comfortable with.---Fwiw--Keoke

[/ QUOTE ]

Yep thats it, The impact wrench does not exceed the possible torque on this nut, but with locktite and the Impact wrench I'm good to go, never, ever had a problem. I had did it this way for many, many years when I found out might be doing something wrong, but it was too late , had had no failures, just rolled my eyes and kept getting it /ubbthreads/images/graemlins/smile.gif
 
Stewart , I hope all this discussion hasn't run you off. Hopefully by now you have already replaced the seal and are driving again. Let us know.

Alan T
 
Not yet it will be another 2 weeks before I get to brave this job. But I will most likely farm the job out if I can find a mechanic to do the job.
 
I was about to do mine also, but all the sudden I'm working every day for a couple weeks. So it's going to a mechanic on Wednesday to take care of a few maintenance items.
 
[ QUOTE ]
but with locktite and the Impact wrench I'm good to go, never, ever had a problem. I had did it this way for many, many years when I found out might be doing something wrong, but it was too late , had had no failures, just rolled my eyes and kept getting it

[/ QUOTE ]

Great.... now I gotta go "search" for more "LocTite" and "Hap" references! /ubbthreads/images/graemlins/jester.gif


Tick, tick, tick...

Actually, it's hard to "overcrush" a crush tube once it's been "set." A "windy" (airtool) would hit "rat-a-tat" before anything like ~bad~ torque was achieved, IMO.

...mebbe should watch those 3/4" drive electric numbers tho. /ubbthreads/images/graemlins/devilgrin.gif
 
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