LSD (Limited slip diff) query / oddity.

My J-Spec facelift car, which apparently has an LSD (according to the VIN plate, and also the seller mentioned it in chit-chat), well it does this "ch ch ch ch" thing when doing 90-degree turns from a standstill, e.g. leaving a side road.

I never noticed this with my UK car, ever. Is this normal? I suppose it sounds like one of the wheels is slipping a bit, but it's very sort of timed, like 500msec between the chs "ch ch ch ch ch" at a normal but slightly enthusiastic accelerating pace.

What I tend to do now is make these maneuvers (htf do you spell that!) slowly now to avoid it.

My UK car definately didn't do this. Is something up, or is it a different type of diff on the facelift import? Digsy's VIN-plate decoder only lists one type of LSD - it's either "Standard (non LSD)", or "Torsen LSD".

I know this sounds stupid, but is the noise coming from the rear or the front? I had that sound on the front and it was my tracking.

Fairly certain it's the rear, but I haven't actually thought about it being the front. Hmmm.

Have a look at this thread (last post on page 1 - Ian C

maybe its a different tyre/wheel issue that means you notice it on your J-spec when you didn't on the uk?

Have a look at this thread (last post on page 1 - Ian C

 

maybe its a different tyre/wheel issue that means you notice it on your J-spec when you didn't on the uk?

Thanks Scooter, that's interesting although I thought the point of the LSD was that it *did* allow the wheels to turn at different speeds. Or is that just the point of an open-diff, e.g. non-LSD? Does the LSD purely and simply just allow grip when the other wheel loses traction?

I have the wheels and tyres off my UK car fitted, so no change there, although the geometry probably could do with being sorted by Chris Wilson when I get some more money - just commited to buying one of his sidemounts so certainly not yet anyway

Rather than spending an hour typing this out, and not making such a good job of it can I direct you here Carl

http://auto.howstuffworks.com/differential.htm

Rather than spending an hour typing this out, and not making such a good job of it can I direct you here Carl

http://auto.howstuffworks.com/differential.htm

Hmm. Doesn't really answer the question. It says that the point of a diff is to allow the wheels to turn at different speeds, i.e. when going around a bend/corner, which is what I thought... until I read Ian C's comments in the above thread about the LSD causing the inner wheel to chirp as it tries to turn at the same speed as the outer wheel.

All the HowStuffWorks thing seems to say is that an LSD is the same as a regular (open) diff, but it also allows torque biasing if one wheel has less traction than the other..

Yeah, well that's it

A limited slip diff only allows a "Limited" amount of slip between the wheels as opposed to an open diff which allows one wheel to spin and the other to stand still.

So yes, with an LSD, when you're going around a tight corner and one wheel has to turn a lot further than the other one you will experience a sort of slipping by the inner wheel because it is being driven forwards rather than being allowed to virtually stand still.

I've got to admit I'm surprised that you get this with the Supra, because they are fitted with a viscous type LSD, which doesn't exhibit these traits so much. A clutch type LSD is a lot more unforgiving.

Are you sure someone hasn't fitted a TRD or similar diff to your Supra?

Yeah, well that's it

A limited slip diff only allows a "Limited" amount of slip between the wheels as opposed to an open diff which allows one wheel to spin and the other to stand still.

 

So yes, with an LSD, when you're going around a tight corner and one wheel has to turn a lot further than the other one you will experience a sort of slipping by the inner wheel because it is being driven forwards rather than being allowed to virtually stand still.

 

I've got to admit I'm surprised that you get this with the Supra, because they are fitted with a viscous type LSD, which doesn't exhibit these traits so much. A clutch type LSD is a lot more unforgiving.

 

Are you sure someone hasn't fitted a TRD or similar diff to your Supra?

Oooh I'll be sure to have a close look underneath

I'm going to check/change the diff oil soon anyway so perhaps I'll be able to tell then.

Thanks very much for the explanation. I understand now why an LSD can cause a limited degree of chirping compared to an open diff. Thank you

No problems Carl, good luck with it

Sounds like you ahve an aftermarket plate type diff. That's good, as the stock one is of little benefit as it's very loose.

Interesting as my car does this and I thought it was normal

My car also does this - and I discovered a few weeks ago that I have LSD.

My car also does this - and I discovered a few weeks ago that I have LSD.

was that in the Arena car park by any chance?

Ah - that was you then was it?

By the time I'm leaving the Arena I'm too knackered to be doing donuts!

Ah - that was you then was it?

 

indeed it was

You guys both have facelift cars, right?

I read a post on here, somewhere, which said that the diff was different on facelift cars. I wonder if that's true?

edit: yup, it seems to be true, but I don't know what the differences are. Nic says that the TRD diffs come in two types - one for pre-facelift, and one for facelift (although he says 97+, so I wonder if it really only applies to VVTi-era facelifts).

Anyone know the ins and outs?

OK, it looks like the the LSD on 97+ N/As (both auto and manual), and 97+ TT Autos was changed from a worm-gear type to a helical-gear type.

My car's a 96 though. There is known to be overlap though. According to that document, 97+ = facelift. I'm obviously half 97+ because I have facelift but no VVTi.

In fact, no. There is no confusion. When they refer to 97+, they simply mean facelift. There is no mention of a VVTi engine in the 97+ new car features at all

I have everything they mention as new in the 97+ new car feature document, as below:

So I guess it's this new helical-gear diff that feels different.

My car is 1996 but non facelift, I should really check my chassis code to see what diff its supposed to have.

Does this mean much to anyone?

My car is 1996 but non facelift, I should really check my chassis code to see what diff its supposed to have.

Manual TTs didn't change from the old type of diff, so you will just have transaxle code B, which is worm-gear TorSen diff in your case. It's either A (open diff, non-lsd), or B=LSD. It doesn't state if it's the updated diff or the original one.

Interesting. Have you got the rest of that New Features doc by any chance?

Interesting. Have you got the rest of that New Features doc by any chance?

Yep, it's all here. It looks to be US-spec though. VVTi is given as a 1998 thing on mkiv.com & mkiv.co.nz.

I get this and I'm not a face-lift.