View Full Version : Big Oil Leak

09-04-2006, 11:09 PM
I just noticed a large oil slick under the rear end of my trusty 1989 ford f150 pickup. It has a 300 inline six cylinder engine and a 5 speed transmission. It appears to be coming from the pinion seal area by the yoke in front of the rear end. Is this a tuff seal replacement job? Or is it possible to do yourself at home. Im not really up on automotive type truck repairs. Opinions any mechanics here thanx Mike

09-04-2006, 11:26 PM
I don't think it's too tough but I've never done it. I will say add some lube if you're still driving it, I just replaced bearings, races ,seals, and 1 hub on a company 89 F350 that ran low on diff lube oil, over $500 in parts.

09-04-2006, 11:27 PM
What rear end do you have,some you can use a screw to remove the seal.

09-04-2006, 11:28 PM
You'll find a big nut holding the yoke onto the pinion shaft of the rear end that's gonna be tight. Typically 200 ft/lbs tight. What I've done is drill a couple of holes into a tube or bar or whatever to bolt to the yoke and hold the damn thing still. Bolt it on in whatever direction jams the bar into the ground, and then get a big pipe on whatever you're grabbing the nut with.

The seal's under the yoke.


09-04-2006, 11:36 PM
I've done a few,first slide under the truck and see if you can shake the pinion up and down.It could be the seal is just wornout and it could also be the bearings are shot.To change the seal you just drop the driveshaft down,wire brush the dirt and sand out from around the pinion nut and witness mark the nut and the pinion,white permanant marker is what I use.

Back the nut off and remove the yoke.The seal just pops out with a screwdriver and a hammer.There might be a groove worn into the yoke neck,but you should be able to get a seal repair sleeve to fit it if it is.Knock the new seal in with a dab of RTV around the od,swipe some grease on the yoke and slip it back on.Clean the nut and the pinion threads with some brake cleaner and put some locktite on the threads then run the nut up snug and bring the witness marks back into alignment plus a couple degrees more.Hang the drive shaft and your good to go.

May as well check the oil level in the rearend,it will most likely be low.If the pinion moves up and down when you shake it,then chances are the bearings are shot and that is a whole nother ball of wax.

Oh,forgot to add,setting the parking brakes down tight will help hold the pinion while your trying to break the nut loose.

09-05-2006, 12:45 AM
Last time Mike mentioned this truck he said he didn't have brakes. :D

A.K. Boomer
09-05-2006, 01:08 AM
Something to check into, I dont know about fords but many a rear end has a crush sleeve that segregates the two pinion bearings, the sleeve is designed to crush at such and such torque and yet the torque rating is slightly higher than when the sleeve starts to crush -- the rest of this added torque goes to pinion bearing pre-load, your not supposed to re-use these sleeves but if you have some horse sense about you you can, (a feel for proper pre-load) it might require you to not go as tight and the use of locktight on the yoke nut... if you have a shim adjustment set up and the pinion is worn and loose you can use the shims to tighten the fit, if the bearings are worn smooth it may buy you some time, if thier pitted it wont buy you much, like everyone else has stated all seals are only as good as the surfaces they run on and if theres tons of slop then a brand new seal can still leak at high rotation speeds because it doesnt have time to adapt to the shaft, driveshafts get wipping so they are prone to this kind of leaking...

09-05-2006, 01:41 AM
I've changed quite a few...just like weird says.
I usually stake the old nut after I torque it. They are really only meant to be used once but staking them with a real sharp center punch will work fine.
If you have a big a$$ impact wrench it'll make removing the nut far easier.

09-05-2006, 11:25 AM
My son had a Dodge truck that suddenly began leaking oil from the rear end after he hit a plastic Wal-Mart bag that was lying in the road, which wrapped around the driveshaft and ground its way into the oil seal. You could pour oil into the diff and it would pump out if he drove a few miles. I was able to get the yoke loose and peel out what was left of the seal, then tap a new one into place with a pipe coupling that fit around the pinion shaft. Worked fine and fixed the leak.

09-05-2006, 12:03 PM
One major advantage to a differential oil leak is that it really cuts down on tailgaters.

09-05-2006, 02:08 PM
{{leaking oil from the rear end after he hit a plastic Wal-Mart bag that was lying in the road,}} I tried to warn everybody about the Chinese and WalMart. That's one of those titanium reinforced bags they are sneaking into the country as we speak. Keep an eye out and avoid at all cost. I think someone pissed off Single Girl....yeah, let her take the blame!

09-05-2006, 05:31 PM
Well basically your problem is that your driving a ford. First, buy a chevy and then... no just kidding

expect that nut to be pretty tight - make sure you either have a beefy impact or some pipe handy. I did one on a GMC and whipped out a 3/4inch impact that worked pretty well. If i could, i probably would've put the 1inch on it but thats too heavy to maneuvere under the vehicle. Besides it really didnt need it...but man those are fun to use! :D

Kevin B.
09-05-2006, 08:46 PM
Check the breather on the differential to see if it's free. A blocked breather will force gear lube past the seal as the unit warms up. Might save you some work.

Kevin B.

George Hodge
09-05-2006, 09:42 PM
Sometimes when you're getting leaks at the rear axle seals,it's caused by the vent being plugged up with mud. Not sure that all axles have a vent on the top of the housing though. Usually it's a small fitting with a loose tophat arrangment.It screws into the housing.

09-05-2006, 10:06 PM
Not much help on the specifics, but my last truck was a 1989 4x2 F150 with the 300 six and 5 speed. went over 300,000 miles. Only got rid of it in 2001, because I was off to the war for a few years. I know where it is now and it still runs. I sure hope my Dodge diesel will go as long as that Ford is.

09-06-2006, 12:02 AM
Well basically your problem is that your driving a ford. First, buy a chevy and then...

.....turn every bolt on it every week forever?:D

09-06-2006, 09:21 AM
.....turn every bolt on it every week forever?:D

Of all the cars I've ever owned, only two came home on flatbeds... and they both had the problem circled right on the grill!!!!

09-06-2006, 05:21 PM
"Of all the cars I've ever owned, only two came home on flatbeds... and they both had the problem circled right on the grill!!!!"

lmao! Thats funny - i like chevy's more than fords but they all have thier problems and advantages...still haven't found the advantages for the fords :D j/k

09-07-2006, 03:04 AM



11-30-2006, 09:21 AM
Sucks to be me i own two of them. A 1984 and the 1989 and they are both running today shame my 2 chevys with 6 cyl in them both blew up.

12-01-2006, 12:37 AM
I crawled under the old truck undid the vent tube rammed a drill (long aircraft series) into the vent Undid the fill plug and pressurized the dif rear end to blow out ****. Also air pressure through the hose. Put it together no leak HM simple fix Once Ahgain ford Uber Alles Hahahaha