10 replies to this topic

[MRD1984]

Hello.

i am stripping my gearbox to do a refurb and noticed the diff planetary gears look all nice and new compared to the rest of the diff... i might be wrong but it looks different to what i remember a mini diff to look like..
the crown wheel has 59teeth
and pinion gear has 19

picture: http://i1261.photobu...28/IMG_1567.jpg

does this look standard??

please help, any info greatly appreciated

thanks!!

[Midas Mk1]

59/19 = 3.1

[MRD1984]

yes i know that thanks but does it look different to a standard diff??

would this be a good ratio for motorways??

[Tupers]

Looks like standard diff to me, possibly rebuilt recently.

[xrocketengineer]

Mine used to look like that!

[Pigeonto]

Looks normal. If motorways was my only consideration I would go a bit higher, probably 2.9. Having had a 3.1 myself. But I think also I'd want over 70 hp and similar torque or its going to be a bit gutless

[MRD1984]

OMG xrocketengineer!!! That is proper f***ed!! Hope it didn't cause too much damage to the other internals!!!
Thanks pigeonto! I am in the process of building a 1310 in my spare moments at work.. So far I have reground the crank and balanced it, balanced the rods and pistons, had the combustion chambers cnc'd bigger valves fitted and ported the heck out of the head.. The compression ration will be 10.2:1 also... With all that I really am hoping for more than 70hp!! I'll be doing something seriously wrong if I can't achieve that!! Lol!!

[xrocketengineer]

I got a new gearbox from Guess-works. Hopefully, I will put the engine back in next week. I have been working on it at my only speed - slow.
By the way, I would recommend to anybody with gearbox problems to replace the oil pump. Mine barely met the wear requirements but it had swallowed some of the shrapnel and spun that against the cover creating deep scratches.

[MRD1984]

Do you know what was the cause of the failure???

[xrocketengineer]

Do you know what was the cause of the failure???

Not definitely. The car is a Japanese Cooper that I bought three years ago and I have not put in 2000 miles on it yet (driving like an old lady). The failure occurred with less than 45000 miles. I had used Mobil 1 15W-50 during that time and the oil was always clean when draining it. The differential pin was worn down to half of its diameter and this can be seen in the picture. The gearbox was very clean with no sludge or deposits of any kind except for all the metal debris. Even the timing chain had absolutely no slack or evidence of wear.
So the wear on the pin can be caused by abuse, soft/improper metal hardness or improper lubrication. I have heard that MPI Minis suffer from improper material on the pin but mine is a 94 SPI. I don't think that differential was abused because everything else shows no wear. And since everything looks so clean good quality oil was being used, possibly synthetic.
So is it possible that synthetic oil caused the failure? Well there is this thread:

http://www.theminiforum.co.uk/forums/topic/53037-synthetic-oil-in-classic-minis/

Quoting entry #14:

I will throw my 2 cents worth in here -- I have been running regular, non-High mileage Castrol GTX 20-50 in my classics year round for a l.o.n.g time and it has worked well. Many moons ago, there was a guy called Crazy Mike that had worked at Seven Ent when they were still in Virginia and he heavily autocrossed a ratty looking but very quick classic Mini with amazing success. He ran M*b*l* One synthetic oil as he wanted to have the "best oil" he could to protect the engine/gearbox. Sometime after he switched to synthetic, the car started to experience differential failure. He asked the manufacturer of that oil if there was a problem using their synthetic oil in the classic Mini. He got a reply that their synthetic oil was fine in the engine, also in the gearbox, but the shear forces generated in the differential (which uses the same oil as engine and gearbox) would break down their synthetic oil and they recommended he not to use it. I actually saw that letter, so this is not heresay, and ever since, I have not considered using synthetic in my classic Minis."

So, maybe it is possible.

[Pigeonto]

... With all that I really am hoping for more than 70hp!! I'll be doing something seriously wrong if I can't achieve that!! Lol!!

........ That will all help but just make sure you do your research and ask enough questions because increased bhp doesnt just happen and it is so easy to be dissapointed.You are right in there now regarding the internals but didnt mention what cam you have? Simply increasing to 1310 will have minimal effect on your output. 70 is only MG metro area so you need much better spec than it had. Oh, and good luck with those huge ports,they didnt work for me,just caused rubbish low down running,fine at full throttle but mine's a road car, and I closed them down again with liquid metal.Research!!!