Differential question
08-18-2017, 10:34 AM
#1
Drifting
Thread Starter
Differential question
Sorry for the simple question, but the behavior of my diff in my base model stripped out 2000 Carerra (2wd 6 speed) has me baffled.
I only mention stripped out since unlike many of your cars, this one only has like 5 option codes ( C02 - cat converter; 424 - CD Compartment; 438 - 3 spoke steering wheel; 450 or 650 - sunroof or light metal wheels; and 698 - Becker CD radio) on the wrinkly and somewhat difficult to read hood sticker. None of them look like a limited slip differential code (220-224?).
So here is what I observed: while in neutral, up on a lift, when I was removing my CV joint bolts, I had to rotate the rear wheels to get access to each of the bolts in turn. What was odd was that each wheel turned independently - when I rotated the passenger wheel the driver wheel didn't move at all and vice versa - when I rotated the driver side wheel, the passenger side remained stationary.
What I was expecting was the wheels to rotate in opposite directions or the same direction, suggesting either an open diff or a LSD. I thought if they turned in the same direction it is a LSD and if they turned in the opposite direction it was an Open diff. But, clearly something isn't adding up.
Full disclosure, I've never had this car running: I purchased it with a known bad engine (appears to be a D-chunk failure). So I've never had it running to verify whether the transmission is any good. For all I know the differential could be blown apart (although, there were no metal bits or glitter in the transmission oil I removed).
Any tips or advice? Do I need to pull the flange and cover to see what's up? Or is this a normal behavior for a 996?
I only mention stripped out since unlike many of your cars, this one only has like 5 option codes ( C02 - cat converter; 424 - CD Compartment; 438 - 3 spoke steering wheel; 450 or 650 - sunroof or light metal wheels; and 698 - Becker CD radio) on the wrinkly and somewhat difficult to read hood sticker. None of them look like a limited slip differential code (220-224?).
So here is what I observed: while in neutral, up on a lift, when I was removing my CV joint bolts, I had to rotate the rear wheels to get access to each of the bolts in turn. What was odd was that each wheel turned independently - when I rotated the passenger wheel the driver wheel didn't move at all and vice versa - when I rotated the driver side wheel, the passenger side remained stationary.
What I was expecting was the wheels to rotate in opposite directions or the same direction, suggesting either an open diff or a LSD. I thought if they turned in the same direction it is a LSD and if they turned in the opposite direction it was an Open diff. But, clearly something isn't adding up.
Full disclosure, I've never had this car running: I purchased it with a known bad engine (appears to be a D-chunk failure). So I've never had it running to verify whether the transmission is any good. For all I know the differential could be blown apart (although, there were no metal bits or glitter in the transmission oil I removed).
Any tips or advice? Do I need to pull the flange and cover to see what's up? Or is this a normal behavior for a 996?
08-18-2017, 12:17 PM
#2
Race Director
Sorry for the simple question, but the behavior of my diff in my base model stripped out 2000 Carerra (2wd 6 speed) has me baffled.
I only mention stripped out since unlike many of your cars, this one only has like 5 option codes ( C02 - cat converter; 424 - CD Compartment; 438 - 3 spoke steering wheel; 450 or 650 - sunroof or light metal wheels; and 698 - Becker CD radio) on the wrinkly and somewhat difficult to read hood sticker. None of them look like a limited slip differential code (220-224?).
So here is what I observed: while in neutral, up on a lift, when I was removing my CV joint bolts, I had to rotate the rear wheels to get access to each of the bolts in turn. What was odd was that each wheel turned independently - when I rotated the passenger wheel the driver wheel didn't move at all and vice versa - when I rotated the driver side wheel, the passenger side remained stationary.
What I was expecting was the wheels to rotate in opposite directions or the same direction, suggesting either an open diff or a LSD. I thought if they turned in the same direction it is a LSD and if they turned in the opposite direction it was an Open diff. But, clearly something isn't adding up.
Full disclosure, I've never had this car running: I purchased it with a known bad engine (appears to be a D-chunk failure). So I've never had it running to verify whether the transmission is any good. For all I know the differential could be blown apart (although, there were no metal bits or glitter in the transmission oil I removed).
Any tips or advice? Do I need to pull the flange and cover to see what's up? Or is this a normal behavior for a 996?
I only mention stripped out since unlike many of your cars, this one only has like 5 option codes ( C02 - cat converter; 424 - CD Compartment; 438 - 3 spoke steering wheel; 450 or 650 - sunroof or light metal wheels; and 698 - Becker CD radio) on the wrinkly and somewhat difficult to read hood sticker. None of them look like a limited slip differential code (220-224?).
So here is what I observed: while in neutral, up on a lift, when I was removing my CV joint bolts, I had to rotate the rear wheels to get access to each of the bolts in turn. What was odd was that each wheel turned independently - when I rotated the passenger wheel the driver wheel didn't move at all and vice versa - when I rotated the driver side wheel, the passenger side remained stationary.
What I was expecting was the wheels to rotate in opposite directions or the same direction, suggesting either an open diff or a LSD. I thought if they turned in the same direction it is a LSD and if they turned in the opposite direction it was an Open diff. But, clearly something isn't adding up.
Full disclosure, I've never had this car running: I purchased it with a known bad engine (appears to be a D-chunk failure). So I've never had it running to verify whether the transmission is any good. For all I know the differential could be blown apart (although, there were no metal bits or glitter in the transmission oil I removed).
Any tips or advice? Do I need to pull the flange and cover to see what's up? Or is this a normal behavior for a 996?
I suspect it is.
Fix the engine. Road test the car.
If the diff is blown -- and I seriously doubt it is -- you'll know it soon enough.
In the meantime I'd leave the diff alone unless you get high confidence info that indicates the behavior you observed is *not* normal and a sign of a bad diff.
Really the odds the car was parked with a simultaneous D-chunked engine and a blown diff are very low.
08-18-2017, 12:36 PM
#3
Put the trans in gear. Your test will work as expected.
When in neutral, the diff will spin the trans output shaft instead of the other wheel if the brakes on the other wheel do not allow it to spin freely due to the car not being driven.
When in neutral, the diff will spin the trans output shaft instead of the other wheel if the brakes on the other wheel do not allow it to spin freely due to the car not being driven.
08-18-2017, 01:38 PM
#4
Drifting
Thread Starter
Perfect, thank you both. I'll take this off my project list. Have a great weekend.
08-18-2017, 05:04 PM
#6
Drifting
Thread Starter
Excellent, that works for me. As long as I have a working differential, I'll be a happy man. Thanks!
08-19-2017, 12:35 PM
#7
Rennlist Member
True. Aside from the clutch, everything else is directly connected, so it's impossible to spin one wheel without something else turning. If it's not the opposite wheel, then it has to be the shaft that connects to the transmission.
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08-20-2017, 12:53 PM
#8
Drifting
Thread Starter
Thank you all, much appreciated.
Without the drag from the brakes, the output shafts turn in opposite directions.
Without the drag from the brakes, the output shafts turn in opposite directions.