Rear End Trouble

[Steve Calzavara]

I have a 2000 Ford Explorer XLT AWD, 5.0. A short time ago, I noticed some oil under the rear end and a whining noise coming from it under deceleration. I cleaned the axle vent tube and added some rear end oil to top it off. However, I'm still hearing the whining under deceleration. Could this noise be coming from the bearings, the seals or the differential gears? Are all differentials in AWD models with a 5.0 the same size? Ideas?

 

[koda2000]

Your diff is worn out. The noise could be the gears and/or the bearings. You'd have to take it apart and check everything, but rebuilding a diff is an expensive and complicated procedure. Being low on oil, or lack of service, may have damaged the diff. The seal's job is to keep oil in and dirt/water out. The seals themselves don't cause noise when they wear out.

You can probably continue to add oil when needed and live with the noise for quite a while before the diff goes out completely, but how long it will last is impossible to say.

I replaced the complete rear diff on my '01 Sport Trac last year. The OP ignored the leaking axle seals and ran it almost completely dry and then got a good amount of water in it and let the truck sit for a year. This ruined everything inside the diff. In my search for a replacement, I learned that all the Gen II ('95-'01) Explorers/Mountaineers 8.8" diffs are the same (4-dr, Sport and Sport Trac, V8 or V6). I bought a used diff w/30 day warranty from a local salvage yard for $300. It came out of a relatively low mileage '00 4-dr. It had the same gear ratio as my original diff (in my case a 4:10) and I swapped in the hole unit. It wasn't very hard to do and the replacement diff turned out to be a good one. Before installing the replacement unit I replaced the axle seals and I would have replaced the pinion seal too, but it was bone dry.

Ford says the synthetic diff fluid does not require service, but I think you need to at least replace the fluid at 100,000 mile intervals and keep an eye out for leaking seals during your engine oil change intervals. If you do that the diff can outlast the rest of the drive train.

I see used diffs on CL for around $200, but there's no warranty there if they're bad.

 

[Jon94]

All 2nd gen Explorers use the same axle housing and will bolt right in to your truck, but they were available with several different gear ratios. You have to make sure the replacement axle has the same gear ratio as your current axle. Check this link to see which gear ratio you have: http://www.therangerstation.com/tech_library/axle_codes.shtml

 

[Mesozoic]

Worn out rear axle. Rebuilding it isn't that bad, as long as you can find a reputable shop that's not taking you for a ride. I would jump for a Detroit Truetrac differential as an upgrade over the clutch type factory limited slip, as the Truetrac functions the same but has no clutches to wear out. A bearing kit will be needed and the ring and pinion should be inspected to see if its ok and not missing teeth, etc. 31-spline Ford 8.8 is a durable solid axle.

 

[Steve Calzavara]

Your diff is worn out. The noise could be the gears and/or the bearings. You'd have to take it apart and check everything, but rebuilding a diff is an expensive and complicated procedure. Being low on oil, or lack of service, may have damaged the diff. The seal's job is to keep oil in and dirt/water out. The seals themselves don't cause noise when they wear out.

You can probably continue to add oil when needed and live with the noise for quite a while before the diff goes out completely, but how long it will last is impossible to say.

I replaced the complete rear diff on my '01 Sport Trac last year. The OP ignored the leaking axle seals and ran it almost completely dry and then got a good amount of water in it and let the truck sit for a year. This ruined everything inside the diff. In my search for a replacement, I learned that all the Gen II ('95-'01) Explorers/Mountaineers 8.8" diffs are the same (4-dr, Sport and Sport Trac, V8 or V6). I bought a used diff w/30 day warranty from a local salvage yard for $300. It came out of a relatively low mileage '00 4-dr. It had the same gear ratio as my original diff (in my case a 4:10) and I swapped in the hole unit. It wasn't very hard to do and the replacement diff turned out to be a good one. Before installing the replacement unit I replaced the axle seals and I would have replaced the pinion seal too, but it was bone dry.

Ford says the synthetic diff fluid does not require service, but I think you need to at least replace the fluid at 100,000 mile intervals and keep an eye out for leaking seals during your engine oil change intervals. If you do that the diff can outlast the rest of the drive train.

I see used diffs on CL for around $200, but there's no warranty there if they're bad.

I believe you've just confirmed what I was afraid of. I'll take the cover off and inspect the gears for excessive wear and then put fresh oil back in. While I have the cover off, I can identify which differential I have. Thank you for the info.

 

[Steve Calzavara]

All 2nd gen Explorers use the same axle housing and will bolt right in to your truck, but they were available with several different gear ratios. You have to make sure the replacement axle has the same gear ratio as your current axle. Check this link to see which gear ratio you have: http://www.therangerstation.com/tech_library/axle_codes.shtml

Thank you. Good info to have. There's a pick-a-part near me. I'll go have a look and see what they have

 

[Steve Calzavara]

Worn out rear axle. Rebuilding it isn't that bad, as long as you can find a reputable shop that's not taking you for a ride. I would jump for a Detroit Truetrac differential as an upgrade over the clutch type factory limited slip, as the Truetrac functions the same but has no clutches to wear out. A bearing kit will be needed and the ring and pinion should be inspected to see if its ok and not missing teeth, etc. 31-spline Ford 8.8 is a durable solid axle.

I don't plan to keep the truck much longer than another year, so spending money on an upgraded rear end is not beneficial. I believe I'll just hunt down a matching rear end, housing and all. But thank you for the response and for the info. Good to have just in case my plan goes south after the year.

 

[koda2000]

I believe you've just confirmed what I was afraid of. I'll take the cover off and inspect the gears for excessive wear and then put fresh oil back in. While I have the cover off, I can identify which differential I have. Thank you for the info.

Taking the cover off, refilling with synthetic oil and resealing the cover just to look can be an expensive proposition. You need 3 qts of 75W140 Syn gear oil @ $12-$18 a qt, and a $7-$8 tube if gasket maker. You probably will not be able to see anything wrong without a complete disassembly. If you just want to know what your diff's ratio is, there should be a metal tag giving info and there should be a sticker on the driver's door jam with an axle code on it (for example - D4 = a 3:73 limited slip diff).

 

[Robman]

When I bought my first explorer.. the rear end whine drove me insane and felt like it dragged a bit.
Took a chance on one a friend had kickin' around from a '96.

I swapped them out and the one I put in had some slop in the pinion going from forward to reversed but other than that the whine was gone and things were good. They were both 3.73s.

Always keep an eye on your axle seals.. they do fail every now and then. Limited slip rear ends call for the synthetic fluid+friction modifier, non L/S rear ends can just take conventional but I put in synthetic either way.