Strange problem

[videodude]

I'm looking at purchasing a '97 Explorer that has a problem: it won't go over 30 mph. The story from the owner is that the rear axle blew it's seals, lost all the lubricant, and french-fried itself. The shop they took it to got a used rear axle, and ever since it was installed, the truck only goes 30.

My gut says that the axle ratio is wrong, and the speed sensors in the transfer case are telling the controller to lock up, which is causing the tires to "scuff", hence limiting forward mobility to 30mph.

Any other ideas? The owner swears that until the rear axle was replaced, they have had no problems with the truck. It's a 4.0 automatic, they are frustrated and want to sell it for 2K. Am I making a mistake to pick this up? Changing a rear axle isn't rocket science, more like about 2 hours easy work.

Thanks,

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[spindlecone]

Wellcome to the site
Keep us posted

 

[sn0border88]

2k isnt a bad price at all if its just the rear. You can junkyard one for a few hundred and your right, it isnt a hard swap. But when you say it wont go over 30... do you mean the brakes lockup at this point? Or it just overrev's?

 

[videodude]

Won't go over 30mph

2k isnt a bad price at all if its just the rear. You can junkyard one for a few hundred and your right, it isnt a hard swap. But when you say it wont go over 30... do you mean the brakes lockup at this point? Or it just overrev's?

No, the brakes don't lock up, and the engine doesn't over-rev, it's a little hard to describe. It's a tire thing. Try to imagine having a 4:10 in the rear and a 3:55 in front, and being locked in 4 wheel. The front will try and "pull" the rear, and the tires will "scrub" the pavement. That's what the owner says it feels like.

I have NOT seen or driven the car yet, that will happen tomorrow. The owner doesn't seem to be mechanically inclined, but I guess that probably goes for the shop they took it to as well. If it ran fine before the rear end blew, and all they changed is the rear (still don't know what they changed, but he told me they got a "used" something, I suspect they changed the entire axle) "whatever", then that seems to be the place to start the investigation.

I guess my question is "Does anyone understand the "full time" transfer case enough to speculate what would happen if the front and rear axles were different ratios?".

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[JDraper]

If they swapped in a rear axle with the wrong ratio, it would fubar the xfer case clutches pretty quickly and play havoc with the u-joints and the rest of the drivetrain. The only way to drive it would be to disable the xfer case (do a search on "brown wire mod") .

 

[videodude]

That's the answer I was looking for!

If they swapped in a rear axle with the wrong ratio, it would fubar the xfer case clutches pretty quickly and play havoc with the u-joints and the rest of the drivetrain. The only way to drive it would be to disable the xfer case (do a search on "brown wire mod") .

My understanding is that after the axle (?) was changed, they quickly discovered that there was a driveability problem, and it went back to the shop, where it still sits. The owner is frustrated and doesn't want to spend any more money on it (and I sure wouldn't, not with THAT shop!), and just wants to get rid of it.

I saw the "brown wire mod", it looks like I could just clip it (in the short run) to drive it home, then do the diagnosis. From what I gathered from the owner, the truck didn't make it farther than around the block, so I doubt that much damage (if any) got done to the rest of the drivetrain.

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[sn0border88]

indeed, try and get the codes off the axles f/r and someone on here can tell you the ratios to see if that is indeed the problem.

 

[BrooklynBay]

Here is the thread on Axle codes: http://www.explorerforum.com/ntrprize/Axle.htm

 

[videodude]

Thanks!

Here is the thread on Axle codes: http://www.explorerforum.com/ntrprize/Axle.htm

Thanks for the axle code link, I was hoping to not have to dig through a manual to find them. Hopefully, the rear axle still has it's tag, or is the code stamped on it? I figure the original ratio should be on the buck plate, and the front axle hasn't been touched.

Film at 11 (more likely tomorrow late afternoon, after I get to see the truck)

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[spindlecone]

10 bux says the problem will never be solved, if it exsists

 

[BrooklynBay]

That thread with the axle codes is in the Explorer specifications forum. If you want to find out anymore information, such as Vin # codes, and other specifications for a specific year, then take a look at that thread. Just click on the forums category on the top of any page. After you see all of the forums listed, just go to the specifications forum.

 

[videodude]

I'll take that as a challenge!

10 bux says the problem will never be solved, if it exsists

This reeks of an idiot mechanic, and a "mechanically challenged" owner. Assuming I get the truck, I think your $10 will be mine! There aren't too many possibilities, from what I can see. If the axle ratios are significantly different (3.55 in front and 3.73 in the rear), the transfer case computer would get confused, and attempt to lock up the front in Auto mode. In Hi lock, it would be exactly the same, as so would Lo lock (except Lo would do serious damage really fast). The other possibility is that either the rear driveshaft speed sensor or the wiring to/from it got damaged when the rear axle was changed, which is unlikely.

The more I read, the more convinced I am that the rear axle ratio is the wrong one to match the front. That also means that I can cut the brown wire and drive it home, after making the deal of the year, and then deal with finding a "proper" rear axle.

Your $10 will help buy the new axle (or the new speed sensor!).

LOL,

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[BrooklynBay]

A lot of people get the rear antilock brake sensor on the differential confused with a VSS (including the mechanics at the Ford dealership). I first read about that in Gears magazine. Some lady had a problem with her motorhome, and the dealer thought that it has 2 Vss's (one on the 4X4 housing, and one on the differential). Their diagnosis was wrong. A mechanic from Gears magazine pointed out to the Ford dealership that it was an ABS sensor, not a VSS on the differential. I think they actually refunded her money. The same person in Gears magazine found a pinched wire in the steering column that was connected to the VSS. When the column was tilted, it shorted out the signal to the computer, and the transmission didn't know what speed the motorhome was traveling at, and started to shift erratically as a result.