So NHTSA, where's the old Cherokee?

Several of my colleagues and I have spent most of this week researching, writing and talking about Chrysler Group's decision to fight the recall of the 1993-2004 Jeep Grand Cherokee and 2002-07 Jeep Liberty.

The whole thing has left me with an unanswered question for the National Highway Traffic Safety Administration: Where's the XJ, the 1984-2001 Jeep Cherokee?

If the early models of the Grand Cherokee -- called the ZJ -- are unsafe, as NHTSA contends, because of the design and performance of their fuel tanks, why aren't the Cherokees equally unsafe?

We did ask NHTSA the question, a couple of times. We just didn't get an answer.

The two vehicles, the Cherokee and Grand Cherokee, have almost the same fuel system -- the same design, the same materials, the same location behind the rear axle -- according to a person who helped design both vehicles. The same fuel system design was largely carried over when the Liberty replaced the Cherokee in 2001.

In fact, with the exception of the sheet metal, the only difference between the Cherokee and those early Grand Cherokees from a design standpoint was six additional inches of space in the back seat, between the B and C pillars.

Yet, at least if Chrysler's analysis of NHTSA's crash data is to be believed, the 1984-92 Cherokee's rate of fatal rear-impact crashes with fire was between the Liberty and Grand Cherokee, while the 1993-2001 Cherokee rate was lower.

Earlier NHTSA communications with Chrysler -- this investigation began in August 2010 -- mentioned the Cherokee, but that vehicle disappeared from view when the official recall request was sent to Chrysler Monday.

A transitive property in mathematics states that if "A" is equal to "B" and "B" is equal to "C," then "A" and "C" must be equal.

So NHTSA, we'll ask again: if the fuel system in the Grand Cherokee and the Liberty are unsafe, and the Grand Cherokee and Liberty's fuel systems are the same as the Cherokee's, why is the Cherokee unequal?

Because that's a stumper.

You can reach Larry P. Vellequette at -- Follow Larry P. on Twitter: