I'm in the process of rebuilding my coupe and wondering if it needs a 4 pin diff, could I please have the forums opinions on this.
I'm fitting a metro turbo engine and box with slight tuning - intercooler, slightly raised boost pressure, avonbar phase 2 cam, high ratio rockers and have already fitted straight cut drop gears as I have always had trouble with these on previous high output engines.
I'll not be using the car for competition or dropping the clutch a max revs at the traffic lights or doing donuts just for normal road use.
What do you think??

If you have a 4pin diff fit it, I've used one in an 1100 Kawasaki race car from 1997 to 2010 with 160bhp at the wheels shod with very soft hill climb 10" slicks and never broke it, I'm now using a Quaife diff which is also very good.
John

For sensible driving then no but if you only ever intended to drive sensibly then you wouldn't be fitting a tweaked turbo-charged engine (OK maybe replace sensible with gentle).

The GTM is harder on it's diff than a Mini because of the extra rear grip. Where a Mini has a sort of safety valve where it will spin the wheels the GTM will more often just dig in and all that torque is transmitted through the diff.

I'd uprate the diff if I was building it.

Iain

It would be sensible to fit a twin crosspin differential.
The extra two planet gears does help with the durability.
If you do go with a twin crosspin differential, I recommend that you get a MiniSpares Molybdenum Cross Pin diff.
http://minispares.com/product/Classic/G ... 0to%20shop

It is so much better that the ones from MiniSport etc.
I have seen the cross pins of the MiniSport ones coming out due to the spirol retaining pins not keeping the crosspin in place - not a pretty sight.

Thanks for the feedback, it looks like 3 votes for the diff and 0 against.
So I'll need to break into the piggybank and call Minispares!
Eric

I would fit a 4 pin diff, standard diff is the weakest part of the gearbox imo. minispares one is the best

I'd agree on balance given your engine spec.
But I'd think you're actually less likely to break a standard diff in a GTM than a Mini.
It's wheelspin that kills the std one, and Mini's do tend to spin their wheels a lot if you're trying

I run a Minispares cross pin diff, it hasn't broke yet, with high boost and nitrous oxide launches on the dragstrip.

Recommended you fit one

+1 for the Minispares diff. Just so happens I was at Minispares yesterday and it was at the top of my shopping list.

On another note, are you guys running pot joints?

I have pot joint son mine, and a Minispares x pin diff.

Minispares diff ordered yesterday
Thanks for the help guys.

Wheelspin doesn't kill the diff - once it's spinning there's very little torque being transmitted and all the diff is doing is spinning. What kills them is when a large amount of torque is being applied and the wheels do actually have grip so it's all being contained/transmitted by the diff. Of course spinning the wheels involves a lot of torque being applied immediately before the wheel lets go and then a fairly large shock load when the spinning wheel manages to grab again but in both these cases it's worse in a GTM than a Mini.

Iain

The standard Mini differentials I have blown up usually have teeth ripped off the planet gears and sometimes the side gears.
I have also broken the pot-joint type side gear shafts.
(I was running about 130bhp into 9" wide sticky slicks on the back of a single-seater hillclimb car)....