Transfer case problem

[travelinman1962]

I have a 96 explorer xlt with a 4.0 engine. This is a control track vehicle. Recently the speedometer started doing a funky jiggle during acceleration and would go to zero when i let off the gas pedal. The check engine light came on and indicated that the vehicle speed sensor was faulty so i installed a new one but the problem persisted. The transmission is shifting erratically because the speedometer signal is fluctuating. I had a diagnostic done and the mechanic said the gear inside the transfer case that meshes with the speed sensor was bad and the transfer case would have to be replaced. It still drives normal when in first or second gear, its just going into 3rd that it sometimes revs then goes into gear. Is the mechanic right or should i get a second opinion? Oh, the tranny was rebuilt about 50,000 miles ago .

 

[Ray Lobato]

I would get a second opinion.

 

[pj8847]

Get a second and third opinion, as well as have the rear t-case bearing checked for play... (you can do this yourself by grabbing the rear yolk/drive-shaft right at the t-case, and seeing if you have any up/down, side to side movement, there should be NONE at all).

you never mentioned how the gear on the sensor looked... any cracked teeth? worn at all? was it replaced with the sensor itself? (usually isn't unless you ask for it to be, and is overlooked most of the time by an average "mechanic") I only ask because if the output shaft has play from a bad bearing or the rear case actually getting out of round/wearing/breaking (known issue with these t-cases) it will cause the teeth on the speed sensor gear to wear or break, and if the gear INSIDE the t-case is plastic (which it is I believe) teeth can be damaged on it as well, causing the exact problem you are having...

I have a '95 that has the unfortunate problem of the rear case damage, and I have gone through 5 or 6 gears on the speed sensor itself as a stop gap measure to keep the truck on the road, but now the gear inside on the output shaft is showing some damage since I haven't replaced the rear case half yet, both need to be replaced SOON for me...

UNDERSTAND, the WHOLE t-case does NOT need to be replaced, Disassembled YES, replaced NO... the gear itself can be replaced, both on the sensor and rear output shaft, and if need be, the rear half of the case itself. Don't get screwed by some "mechanic" looking to make a buck on the notion that you don't know what is going on.

Take it to a few trusted 4x4 or transmission shops, get a few opinions. It could be as simple as the gear on the speed sensor just being old and worn out... a $25, 10 minute fix, tops! (if of course the needed replacement is on hand)

P.S. My opinion on what it *may* be, just by your description of symptoms is that you may indeed have a bad rear bearing, or the rear case problem as well... jumping around under acceleration and then dropping to zero when you let off the gas suggests the rear output shaft is in fact moving, enough that it effects the mesh of the 2 gears, making them skip, which will cause the "bounce" and/or not even mesh at all at some points, resulting in a zero reading....

Let us know what you find out...

 

[travelinman1962]

Thanks for the input. I think i am going to buy a rebuild kit to replace the bearings, seals and other minor things. If i see other damage i can always buy that part. The mechanic did say the rear output shaft was really wobbly so hopefully it hasn't caused any internal damage. I just wonder how hard it is to remove the trans case from the tranny.

 

[pj8847]

The mechanic did say the rear output shaft was really wobbly so hopefully it hasn't caused any internal damage. I just wonder how hard it is to remove the trans case from the tranny.

If the rear shaft is wobbling, then either the bearing or the case is toast. Only way to find out is to tear it apart, but, at least you have found the cause of the problem.

The t-case isn't too difficult to remove, have a long extension and wobble (or "u" joint) and the bolts wont be hard at all to get at. Actually dropping it down once it is all unbolted/disconnected may be the hardest part depending on what kind of jack/lift used, or if you are manually dropping onto your chest with your bare hands!

Regardless, you may want to look into having a spare rear case half when doing the tear down so you're not looking/waiting for one with it sitting apart. worst case scenario is if you don't need it, you can always sell it to someone who does (and someone WILL eventually need it). Usually the case is damaged before the bearing though, unfortunately...