First off I want to thank all the respondents concering my differential leak. And I am going to take their advice and do a fluid change and attempt to clean the breather. At the risk of starting a major conflict I would like to know what you experts recommend for the brand and type of gear oil to use. Right now the best match I have found is Valvoline 80/90. That matches the specs. Some have recommended synthetic. I have never used that in a differential.

Please let me know what your recommendations are.

Thanks

 

A very wise man I see.

 

I'm staying with the fossil stuff for now, but I did use synthetic in the tranny. I think Grant Francis will have a say on this.

 

The main stumbling block with the 'which is better' questions is lack of long term results. Since the diffs normally last the lifetime of the car when using the standard lubricant, it's pretty hard to prove that a substitute is better.

 

A few years ago I thought my Z3 diff. had too much rotational play in the output shafts so I refilled with Royal Purple 80-140 or something like that. The click did go away when letting off the gas, but it wasn't leaking.

 

I am using Redline 80W140 full synthetic.

Another member is using Ford/Motorcraft 75W140 full synthetic. I may be switching to the same.

 

Probably the anti-shock additive because they sell to the drag racing market.

 

I thought the book specified Shell Super Spirax 90.

 

It does. But that is not normally stocked in auto stores or even Shell stations. If I go with that I'll have to special order it. But since that was eighteen years ago I thought there might have been some improvements especially in the area of leak protection.

 

I know that in the UK Opie sell it (at £13/litre) but I'm having enough trouble with the other end of my car without worrying about my diff at the moment so I haven't really looked into it.

I recall the book was fairly flexible on gearbox oils, in that it offered a selection, but it was quite specific that only Shell Spirax Super 90 (or some combination of those words) should be used for the diff. I wonder if that was because that's all they tested, or they had a deal with Shell, or it had some mysterious magical properties?

It does remind me of how you're only supposed to fit Pirelli P6000 tyres and if you do dare fit another brand, they insist you inflate them up to some ridiculous pressure for 'safety'.

 

I usually change the oil yearly and use whatever my indie has in stock but after the gear change and full rebuild I put redline shockproof one thing its expensive

 

You change your diff oil every year?

 

Yeah I used to change the diff oil and service transmision yearly with the cost of the redline shockproof I will stretch it to 3 years I was informed that the diffs in xj40 onwards can have problems and he was of the belief it was due to the diff being high up in the car and not in the airflow so if by yearly oil changes I can avoid problems ill try also it is very hot here in winter it doesn't get under double digits and summer like today its 32 degrees and 75 % humidity

 

i have replaced mine with mobil syn 75-90

 

Just thought I would post the final results of my differential leak problem. To refresh everyone I had a leak around the right side flange holding the half-shaft bearing in. I read all the good advice from everyone and then picked the advice I liked best. I changed the fluid with Castrol 80-90 limited slip fluid. Didn't need the limited slip, but that was what was on the shelf. Cleaned around the breather cap as best as I could. I discovered you could rotate the cap which I did back and forth several times. I hope that lossened and crap that might have plugged it or caused the check valve to stick. Didn't pop the cap off since I wouldn't be able to put it back on. I did consider doing that and connecting a plastic tube to the stub of the breather and putting a remote breather on the other end of the tube and routing it above the differential. The off road guys do this to insure no water gets in. Anyway, after refilling with new fluid and cleaning all the leaked oil off I have a dry differential with no leaks so far.

Thanks guys for all the help and good ideas.

 

does that oil have "extreme pressure" rating on it?

I'd like to try this in the summer .. but the XJR has a part of the suspension brace right in front of the breather,.. it's very difficult to hook up a tube on it.. there's almost zero room to do anything.

 

As far as an extreme pressure rating there is not such a rating on the container just says maximum gear protection. I never drive my car hard. That is I do not ever damand high torque output and almost never over 70 mph. Where I live high speeds are not a good idea or you might wind up with deer antlers for a hood ornament. And the secondary roads are not good enough for real high speeds. And besides the price of gas and distances I need to travel economy is the by word.

I understand the breather concern. I would try rotating it with your hand if you can reach it with your fingers. If it rotates easily I would say it is not clogged. We had on member say that he pried off the breather cap and when it came off it really popped off. That tells me it was clogged. The differential will build up pressure if the breather is clogged. If the breather is working properly it will have a slightly negative pressure when it cools down after driving. Opening the filler plug will result in a sucking sound. There is a check valve in the breather that keeps water from getting in and lets air out. If you want to know more about remote breathers google Toyota differential breathers. The off-road guys work the problem a lot as they go through water that covers the differential.

I would think that you could fashion a 90 degree elbow out of a plastic connector that would fit over the stub that is left after you pop off the cap. But try rotating the cap first and see if your leak doesn't go away after you change fluid.