Leaking Differential
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Leaking Differential
I have a '99 F150 4x4 (extended cab) with limited slip rear differential. The seal at the drive shaft has developed a small leak. I'm wondering how difficult it is to replace this seal and how to do it. Any help is appreciated.
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From: Houston, Texas
That is called the Pinion Seal.....and depending on the method that axle uses to hold the bearings around the pinion gear, this process can become quite difficult. There are two ways that I know of that these bearings are held in place......with shims and with a crush sleeve. If your axle is a crush sleeve axle, then the process can be more difficult.
I have replaced a pinion seal on a crush sleeve axle and it wasnt as bad as I thought.....although I didnt follow the instructions given in my FSM (that said to measure the preload on the pinion gear prior to removal and to add 5in-lbs when reinstalling) and simply tightened it to less than what it was before so as not to crush the sleeve any more therefore affecting the bearings.
You might want to find out what type of method this axle uses to hold the bearings in place.
Also, there is a reason that the pinion seal is leaking. You need to determine why. The seal on my jeep was leaking because I smashed the front driveshaft on a rock and drove for about a week before pulling it and having it straightened and rebalanced. Of course, the rubber on your pinion seal (which is rubber on the innermost part and metal everywhere else) could just have some dry rot.
How bad is this seal leaking? Mine was dripping a puddle on the ground before I got around to replacing it.
I have replaced a pinion seal on a crush sleeve axle and it wasnt as bad as I thought.....although I didnt follow the instructions given in my FSM (that said to measure the preload on the pinion gear prior to removal and to add 5in-lbs when reinstalling) and simply tightened it to less than what it was before so as not to crush the sleeve any more therefore affecting the bearings.
You might want to find out what type of method this axle uses to hold the bearings in place.
Also, there is a reason that the pinion seal is leaking. You need to determine why. The seal on my jeep was leaking because I smashed the front driveshaft on a rock and drove for about a week before pulling it and having it straightened and rebalanced. Of course, the rubber on your pinion seal (which is rubber on the innermost part and metal everywhere else) could just have some dry rot.
How bad is this seal leaking? Mine was dripping a puddle on the ground before I got around to replacing it.
Hotshot
Joined: Aug 2002
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From: BC, Canada
Hi Finatic and welcome to the forum 
Your truck does use a crush sleeve. If you dont tighten the pinion nut correctly you can damage the pinion bearings.
Like Jeremy said if something is bent or whatever it can make the seal fail sooner but they also do fail without any extra help.
To replace the seal you'll need a 12 point 12 mm socket or wrench for the driveshaft bolts, a 1 1/8" socket and long ratchet or breaker bar or air impact for the pinion nut, a 2 or 3 jaw puller to remove the flange, or yoke as some people call it, as well as a hammer etc.
If you're not sure you want to tackle it yourself I would take it to your dealer and have them do it. Flat rate is approximately an hour @ whatever they charge an hour. I dont know what the seal is worth but I'd guess $15. They will also top up the oil so figure on a few bucks for that. If the oil in the diff has never been changed it might be a good time to do that. The 75W-140 synthetic oil that Ford uses is quite expensive but it's what they recommend.
Your truck does use a crush sleeve. If you dont tighten the pinion nut correctly you can damage the pinion bearings.
Like Jeremy said if something is bent or whatever it can make the seal fail sooner but they also do fail without any extra help.
To replace the seal you'll need a 12 point 12 mm socket or wrench for the driveshaft bolts, a 1 1/8" socket and long ratchet or breaker bar or air impact for the pinion nut, a 2 or 3 jaw puller to remove the flange, or yoke as some people call it, as well as a hammer etc.
If you're not sure you want to tackle it yourself I would take it to your dealer and have them do it. Flat rate is approximately an hour @ whatever they charge an hour. I dont know what the seal is worth but I'd guess $15. They will also top up the oil so figure on a few bucks for that. If the oil in the diff has never been changed it might be a good time to do that. The 75W-140 synthetic oil that Ford uses is quite expensive but it's what they recommend.
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I did this once on my F-150. The seal from the dealer was 12 dollars. It is not to hard, but to be honest if I ever need it done again. and a shop is only going to charge an hour labor like Racerguy said, the shop will be doing it. That is unless i have a lift to use. Not a fun job on your back.
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Thanks for the replies. The seal is not leaking very much...I just noticed a spot on my garage floor about the size of a half dollar and this is from several days if not weeks. When I checked the fluid level, I could stick my finger just inside the hole and feel the level, so not much has been lost. Fluid has never been changed as far as I know (I bought the truck used in 2001). It has 63k miles now.
I haven't done any heavy offroading, just driving around in bean fields so I don't think I've damaged the driveshaft. I do use the truck to launch a boat in saltwater, and usually water will splash over the axle and differential. I rinse the underside of the truck at the same time that I clean the boat up.
I noticed this leak while replacing the RABS sensor. I also noticed that the sensor had grease on it when I took it out and the fluid fill plug did as well. Is the axle packed with grease and then fluid is added as well? Just wanted to make sure that water isn't getting into the case and causing the fluid to gel. The fluid is still clear, not milky like I would suspect if moisture was present.
I think it is just normal wear and tear. Any thoughts?
I haven't done any heavy offroading, just driving around in bean fields so I don't think I've damaged the driveshaft. I do use the truck to launch a boat in saltwater, and usually water will splash over the axle and differential. I rinse the underside of the truck at the same time that I clean the boat up.
I noticed this leak while replacing the RABS sensor. I also noticed that the sensor had grease on it when I took it out and the fluid fill plug did as well. Is the axle packed with grease and then fluid is added as well? Just wanted to make sure that water isn't getting into the case and causing the fluid to gel. The fluid is still clear, not milky like I would suspect if moisture was present.
I think it is just normal wear and tear. Any thoughts?
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From: Houston, Texas
If the fluid is not milky, then no water is getting into the axle. It can however, get in easily through the axle seals, but it sounds like all of your seals are diong their job if the fluid is clear.
As for the pinion seal.....if you are going to replace it yourself, I'd drop the driveshaft and back the pinion nut off (holding the yoke with a pipe wrench) and then pull out the old seal. I pulled mine without a puller......it took a few minutes and I almost completely destroyed the old seal, but that didnt matter. To install the new seal, I took a 2x4 and drilled out a hole so that I new the 2x4 would fit over the pinion gear shaft and hammered the seal in place. I reinstalled the pinion nut using a regular 1/2" drive socket wrench (tightened it.....but did not CRANK down on it) and held the yoke with the pipe wrench. refilled with oil and reinstalled the driveshaft and was ready to go. Took about an hour or so.
As for the pinion seal.....if you are going to replace it yourself, I'd drop the driveshaft and back the pinion nut off (holding the yoke with a pipe wrench) and then pull out the old seal. I pulled mine without a puller......it took a few minutes and I almost completely destroyed the old seal, but that didnt matter. To install the new seal, I took a 2x4 and drilled out a hole so that I new the 2x4 would fit over the pinion gear shaft and hammered the seal in place. I reinstalled the pinion nut using a regular 1/2" drive socket wrench (tightened it.....but did not CRANK down on it) and held the yoke with the pipe wrench. refilled with oil and reinstalled the driveshaft and was ready to go. Took about an hour or so.
