6 replies to this topic

[lsto]

Hi all, my diff on my daily has developed a bit of slop so assuming the pin is wearing. A+ 998 fast road engine.
Question is 1, do I change just the pin for the mini spares C-BTA166, go for the pin and planet kit C-BTA167 or am I better off just going for the cross pin diff C-AJJ3385?
Question 2, how difficult is it to drop the diff while the engine is in the car or is it not worth messing about and just pull the engine? I know it won't be fun setting the preload in the car.
Cheers

[Cooperman]

You have to remove the engine.
For a 998 it’s not really necessary to go to a cross-pin. They are really for rally cars and very powerful 1275’s.
Get a top quality pin from Mini Spares and a set of planet wheels with the thrust cups, etc, and rebuild it. It will last a long time.

[Ethel]

Question 2 - Very. You'd have done almost everything but lift the engine. Lifting it will make working on the diff so much easier & likely to go well.

[lsto]

Thank you for the replies. I had a feeling id have to pull the engine so thanks for confirming.
Looks like if I'm pulling the engine I may as well take the opportunity to upgrade to a lightened flywheel.
On that note, if I purchase a flywheel and clutch kit, can I get them balanced at a normal machine shop or am I going to have to hunt out someone like AC Dodd to do it for me?

Thanks again

[Cooperman]

To balance an engine properly requires the flywheel, crankshaft, clutch and front pulley to be out of the engine and put together as a sub-assembly.
The need for balancing is determined by the max revs you will be using. For sustained or regular use over about 6200 rpm with a 998 a fully balanced bottom end is desirable, but below that you might as well save your money. To get a fully balanced engine you are taking a full strip and rebuild.
Start by asking yourself what the car is to be used for. If it is for competition then it is a whole different game and you will be spending big money.
If it is only a road car a nicely built 998 will keep up with modern traffic, but it will never be a ‘fast road car’ compared with modern cars. For example, my wife’s 1.5 litre Fiesta Diesel has about the same performance as a Mk1 Cooper ‘S’, except for max speed when the Fiesta is quicker.

[Spider]

You'll want to replace the Pin, thrusts, planet gears and their thrusts. I'd suggest the standard planet gears, though that have a bush fitted I've seen plenty split as the wall thickness on the small end gets very thin. You'll want a Pin that has the hardest case you can find.

A cross Pin diff is worthwhile if you do a lot of cornering, as the wear is more related to how often there's a difference in speed between the two front wheels than the power put through the diff, though, that is a factor.

You may also find the bushes in the hemisphere and crown wheel may have wear and need to be replaced. These need to be sized after fitting, ideally, in a lathe. While you have it all apart, you may also find the bushes in the side covers need replacing too and it's the same deal with them.

[lsto]

I fully get that, when I said fast road I really meant just modified. I tell people it's not fast it's just less slow.
It is a turbocharged daily, nothing nutty just running 7psi boost with a home worked head, 266 cam and standard bottom end. I was under the impression that flywheels and clutch assemblies were meant to be balanced or it can cause vibration problems?
If not I'll just order mini spares lightened flywheel and bolt it straight on and save myself some money.
Thanks for the help