[junglejustice]

Well - a bit of a loaded question here (since I already know the answer), but I am posting this for a friend here who may be a bit too embarrassed to ask the question himself...

In a traditional "locked" rear differential setup (or with any American-type LSD), you can raise the drive-wheels off of the ground and turn one wheel forward and watch the other wheel turning forward with it and that is one sure-fire way of knowing that you have an LSD in your differential or not!

Without coaching anybody here, can someone please tell us what happens when you perform this simple "test" on an Alfa Romeo transaxle WITH an installed LSD?

 

[sh0rtlife]

ive asked this one a few times and NEVER gotten a straight answer......your right tho..traditional units are obvious

 

[Giorgio68]

My way of testing an LSD transaxle is, put your car on a first gear rev the RPM at 5000 then release the clutch, if you see 2 black tire marks on the ground then you know you have an LSD transaxle. This is the old school way.

Giorgio

 

[Hit an Apex]

My way of testing an LSD transaxle is, put your car on a first gear rev the RPM at 5000 then release the clutch, if you see 2 black tire marks on the ground then you know you have an LSD transaxle. This is the old school way.

Giorgio

I do not have an LSD transaxle and I can do that

 

[5yearplan]

Well, my '85 BMW 535i with an LSD, and when I jack it up and start it the rear wheels spin a little (in neutral). Does this have anything to do with the LSD?

 

[BigSwede]

The only way to be really sure is to open the tranny and look.
Lifting the wheels and spinning isn't really going to give you anything, it will only work if your pinion is not tight enough. i.e. you can see weather the drag torque in the speedgears/bearings are larger then the clutch packs.

 

[C&S]

I always thought the best way was to park one wheel on gravel (or grass), the other on tarmac, and dump the clutch. Either you sit there and spin one wheel, or you start to accelerate. Always worked for me.

I've never been game to dump the clutch in my transaxle Alfas on a dry road. Do people actually do that? maybe if I could drive someone elses?

 

[BigSwede]

I do that all the time in my racecar...

The "one wheel on gravel" approach doesn't really give you the whole story, the LSD will transfer 25% extra of the available torque on the slippery wheel. So if you are on ice with one wheel you can transmit next-to-nothing+25% extra to the other wheel, i.e. you will spin the wheel anyway.

 

[C&S]

You'll spin the wheel, but still accelerate surely?

But with a non-lsd on gravel/grass/ice you'll get nowhere?

 

[drew`SEVNT5]

I always thought the best way was to park one wheel on gravel (or grass), the other on tarmac, and dump the clutch. Either you sit there and spin one wheel, or you start to accelerate. Always worked for me.

I've never been game to dump the clutch in my transaxle Alfas on a dry road. Do people actually do that? maybe if I could drive someone elses?

I do.


Often.


And always at redline...also, a clutch kick to get 'er nice and sideways on a wet road too...

 

[bobsiopener]

I've heard that one way is to be in an emtpy parking lot turn the wheel to one direction and drop the clutch. If the car snaps around then its LSD if it doesn't snap then no LSD

 

[BigSwede]

You'll spin the wheel, but still accelerate surely?

But with a non-lsd on gravel/grass/ice you'll get nowhere?

Very slow acceleration, sure. Not a very digital way of telling if you have a LSD or not since a car will accelerate spinning it's wheels on gravel even without LSD.

 

[junglejustice]

The only way to be really sure is to open the tranny and look. Lifting the wheels and spinning isn't really going to give you anything, it will only work if your pinion is not tight enough. i.e. you can see weather the drag torque in the speedgears/bearings are larger then the clutch packs.

Well, while the key (last) part of my original question wasn't quite answered yet, I think that Mats' answer came closest to what we were looking for; you CAN'T!

There are no physical visual/discernable differences between a standard and an LSD Alfa transaxle - at least not externally! You have to open it up to be 100% sure. In fact, you can take an LSD "pumpkin" and install it in a previously (non)LSD transaxle, shim it properly and now have an LSD in a transaxle that previously was not an LSD transaxle!

Here's the smoking gun question in all of this: Can you simply put an Alfa Romeo transaxle car with (suspected) LSD up in the air on a lift, turn one of the drive-wheels in one direction, watch the other wheel - either remain motionless, or even tend to "want" to move in the opposite direction - and conclude that the vehicle in question does NOT have an LSD in it?

 

[AR4me]

Can you simply put an Alfa Romeo transaxle car with (suspected) LSD up in the air on a lift, turn one of the drive-wheels in one direction, watch the other wheel - either remain motionless, or even tend to "want" to move in the opposite direction - and conclude that the vehicle in question does NOT have an LSD in it?

No: My budget race car has a 50% lock-up LSD (which I installed in the transaxle myself along with assembling the transaxle, and it is pretty obvious from running it on the race track - no more spinning inside rear tire coming out of turns trying to put down power), and since it is on jack stands in the garage, I went to spin either of the rear wheels. The opposite basically doesn't move, perhaps a slight tendency to wanting to spin in the opposite direction.
Jes

 

[BigSwede]

Well, while the key (last) part of my original question wasn't quite answered yet, I think that Mats' answer came closest to what we were looking for; you CAN'T!

There are no physical visual/discernable differences between a standard and an LSD Alfa transaxle - at least not externally! You have to open it up to be 100% sure. In fact, you can take an LSD "pumpkin" and install it in a previously (non)LSD transaxle, shim it properly and now have an LSD in a transaxle that previously was not an LSD transaxle!

Yep, I have two of that type, did them myself.

Here's the smoking gun question in all of this: Can you simply put an Alfa Romeo transaxle car with (suspected) LSD up in the air on a lift, turn one of the drive-wheels in one direction, watch the other wheel - either remain motionless, or even tend to "want" to move in the opposite direction - and conclude that the vehicle in question does NOT have an LSD in it?

No, it's only a brake, the diff itself will work just like intended, in gear (engine shut off) - you can't spin one wheel in one direction and have the other one stand still. If you can that differential is in bits and pieces.

 

[AR4me]

...the diff itself will work just like intended, in gear (engine shut off) - you can't spin one wheel in one direction and have the other one stand still. If you can that differential is in bits and pieces.

As can be deduced from Mats' post, my above observation was with transmission in neutral. With transmission in gear the opposite wheel spins the opposite direction when I turn one wheel by hand (this LSD has about 50% lock-up). This is just to document how an LSD equipped transaxle behaves, and is not to say that if your transaxle exhibits this behavior then it has LSD!
Jes

 

[junglejustice]

...in gear (engine shut off) - you can't spin one wheel in one direction and have the other one stand still. If you can that differential is in bits and pieces.

Yeah, no - that's fine - obviously!

Thanks for the answers guys - we are talking about in neutral - spin one wheel and the other one pretty much stands still. We have an Alfa EXPERT telling the guy that there is no LSD in the TA...!

 

[BigSwede]

Both of you are describing brake drag, commanly found on Transaxle cars...

 

[Alfar7]

LSD test

Very simple.
Put the car in neurtal, jack up either side (one tire) If the LSD is set up correctly (free) you will be able to turn the tire with some feel of resistance caused by the spider gears turning and the viscous interface on the clutch disk and floater plates.
If you try quick increases in the rotation it should lock up, in either direction.


JJ:
You know YOU really didn`t know did you, and you were supposed to be the great expert!

"Mean Old Bastard"

 

[jazig.k]

locking up in both directions is the action of a 2way LSD. The ideal LSD for the drifters out there. while mid-drift you can back off and on the throttle and it should stay locked. much better control.
im led to believe all LSD transaxles are 2way's.

findout wether you have a LSD. drift it in the dry lsd's and non's act completly different. drift it on dirt and the difference is huge with a 2way.
burnouts. iv seen LSD's [1way] single spin and kick in to a twin spin later on in the skid or not at all. sometimes just twin spin.

iv watched a friend do the half tarmac and half dirt thing in a holden non lsd. with both wheels on tarmac the right hand side always spins in any non lsd holden. his was the same. but he was parked and thought he'd show off with the right side on the tarmac and left on the dirt . kick the throttle and apply a little brake [automatic] the left just spun on the dirt and he didnt move anywhere. kept it going and when the left hit the road it slowed quickly and changed sides.