CDL question

[IH8RDS]

I have been trying to rack my brain and figure this out. I am trying to understand how a LR transfer case works. Is a CDL equipped transfer like a Command-Trac NP231J or is it more like a Selec-Trac NP242? Does it have high and low range? Could someone put in in a perspective that a Jeep Cherokee owner could understand?

Thanks,

 

[James86004]

I looked at a description of the Jeep transfer cases here http://www.answers.com/Command-Trac, but none of them seem to match up.

The Series trucks, up to 1983 or 84, used a part time 4wd system. You could be in rear wheel drive only in high range, or you could engage a dog clutch to connect the front and rear driveshafts. You could shift to low, where that dog clutch was automatically connected. This seems closest to Command-Trac.

The Defenders, the Discoverys, and the early Range Rover Classics used a full time 4wd system. It had a differential in the transfercase that could be locked or unlocked at will in either high or low range by moving the transfer case lever sideways (the CDL). When it was unlocked in high range, you could spin a wheel easily on wet roads because all the power can be sent to one wheel out of a possible 4.
This seems closest to the Quadra-Trac without the limited slip feature.

Range Rovers from 1989 on had a viscous coupling that would automatically lock or unlock the CDL, so their transfer case levers can't move sideways. Similar to Quadra-trac?

 

[kevb]

Assuming you are talking about a D1/D2, Defender, RRC & P38 LR then they have a full time 4 wheel drive system with 3 differentials, one on each axle and one in the transfer g/b. these need to be open for road use to allow the wheels to rotate at different speeds. Most LRs of this type have a locking centre diff for use off road only. this ensures a 50/50 split front to rear, unfortunately LR in their wisdom decided to omit it for the D2 around 2001 to 2003. Without the centre diff locked you can effectively become 1 wheel drive when you lose traction. They all have a high and low range. series LRs have part time 4 wheel drive with high/low. There is no centre differential and the drive is locked 50/50 front rear when in 4wd.

 

[IH8RDS]

To clarify, yes I am talking about the Discovery I in particular. I'm sure those are really good explanations, but I still don't get it

When I put my 231J transfer case in 4WD (low or high) doesn't that give me 50/50 spit between axles? I am trying to look at it know as an actual differential. The 231J is chain driven. I am not supposed to drive it on dry pavement, so maybe it is equivalent to a CDL? It is starting to come around, but you may have to dumb it down some more.

I appreciate you help!

 

[IH8RDS]

One more thing to add. I understand the concept of a locker. I run ARB's front and rear. Just trying to understand how the Discovery transfer cases work.

 

[Maryland 110]

The transfer case is like yours in that its got high and low ranges. The best way to think of the CDL is as "locking" the front and rear drive shafts together at the transfercase. Turn for turn with zero slipage. Neat feature, makes a horrible sound when you blow one up, fortunately thats hard to do.
:beer:

 

[Hank]

Think of the transfer case as a 3rd axle for a minute. The Diff, in Center Diff Lock, is the......diff.

The lock, is just that - a locker. So, by locking the locker, or diff, you're now driving both axles.

 

[IH8RDS]

So with the CDL is "unlocked" in a Discovery transfer case you can drive on dry pavement in 4WD, high or low. (I am thinking like an all wheel drive and allows slippage). When you "lock" the CDL it makes it to a no slippage transfer case like what I have now.

I am starting to understand first two posts how they said it is more like a NP242. That transfer case allows you to run on pavement in full time 4WD or a no slippage part time 4WD.

Am I starting to understand correctly?

 

[traveltoad]

If you understand how an ARB locker works... it is the same idea. But at the transfer case linking front and rear axles rather than left and right wheels.

 

[traveltoad]

So with the CDL is "unlocked" in a Discovery transfer case you can drive on dry pavement in 4WD, high or low. (I am thinking like an all wheel drive and allows slippage). When you "lock" the CDL it makes it to a no slippage transfer case like what I have now.

Am I starting to understand correctly?

Pretty much right on.

 

[IH8RDS]

OK:wings: WHEW! Thank you ALL for you're help!