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Changing rear diff oil on my 68 Deville. Any tips? Other things I should do?

Started by speach, March 28, 2012, 10:38:52 AM

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speach

I am under the impression that my rear differential has not been serviced in a long time. I just finished freshening up the motor and want to get my car in daily driver condition for now. So it appears that I need to take the drive shaft and axle housing off. The bolt hole on the rear seems to high to drain anything. What els can anyone recommend doing while I am doing this work?
Current cars:
1986 Military Chevrolet Diesel G30 Box Van
1968 Conv DeVille
1989 Toyota SpaceCruiser


You cant take your car with you in the end so drive the dang thing.

WilliamTrausch

curly

If there is no drain plug in the lower part of the housing, go to the parts store and buy a transfer pump. Looks like a giant hypodermic needle.  Put the rubber tube in the differential through the fill hole and use the siphon to remove the oil.  It won't get it all, but it will get most of it out.    A lot easier than pulling the differential out!

The one I use is similar to this one : http://automotive.hardwarestore.com/89-552-fluid-transfer-pumps/fluid-transfer-pump-661998.aspx  except mine only has one hose.  They make plastic pumps as well, but I think Diff oil will be too thick to pump for those.

T. Lewis

Gene Beaird

According to the 1968 FSM: 

"Draining and refilling of the differential is necessary only at time of replacement."

That said, certainly thought, 44 year old 90-weight is probably getting pretty tired.  I didn't see a drain plug on the diff of our Calais when I was doing the brakes and changing the oil in it last month.  I'm figuring you'll have to suck the oil out via the fill hole.  A transfer pump will certainly speed things along, but you may be able to accomplish a pretty good evacuation of the old oil, albeit a little slowly, by just getting a length of vacuum hose that fits the fill hole and attaching it to an empty gear oil container.  Squeeze a bunch of air out of the container, drop the hose into the diff and release the pressure on the bottle, letting it re-inflate, sucking the gear oil along with it.  Again, it may take some time. 

You're not going to get it completely empty, but that's okay, most is probably better than none.  Refill with 90-weight, unless it's a 'Controlled Differential' or posi-track. 

Gene Beaird,
1968 Calais
1979 Seville
Pearland, Texas
CLC Member No. 29873

speach

Well it is leaking a bit so I thought I would clean it all up and install new gaskets. What about the differential bearing? 
Current cars:
1986 Military Chevrolet Diesel G30 Box Van
1968 Conv DeVille
1989 Toyota SpaceCruiser


You cant take your car with you in the end so drive the dang thing.

WilliamTrausch

Dave Shepherd

Quote from: speach on March 28, 2012, 12:25:42 PM
Well it is leaking a bit so I thought I would clean it all up and install new gaskets. What about the differential bearing?
Bill the are 4 bearings, 2 pinion bearings and 2 side differential bearings, these diffs were not overhauled in the field back then, so fresh oil and if is quiet let it fly.  The pinion seal can be replaced if that is the leak.

speach

Thanks. I did read an earlier post concerning the diffs up till 70 that are extremely difficult to service and that the dealer did it. Yea I think it is good but the seal is a great idea. Thanks again
Current cars:
1986 Military Chevrolet Diesel G30 Box Van
1968 Conv DeVille
1989 Toyota SpaceCruiser


You cant take your car with you in the end so drive the dang thing.

WilliamTrausch

Jim Beard

Make sure you wear rubber gloves or your hands will stink for a week. Old diff fluid really stinks.

TJ Hopland

Have you already looked at and serviced the rear brakes?   If not I would look there before going into the diff.  Not sure about the year you are working on but with age and miles the axle seals often leak.  Some models to remove the axles and replace the seals you have to remove clips from inside the diff.   Other models they are held in by the bolts that hold the brake backing pates on.  Either way you would want to drain the oil at the same time so doing the brake work, axle seals, and diff oil change all ends up being related.  Any gear oil or brake fluid in the brakes makes them grabby and weird.  Seems like 90% of the vehicles I have ever bought used have needed the seals replaced.  Only one time did they also need bearings. 

StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Gene Beaird

It's either his '66 or '68, so it's definitely NOT a c-clip type diff.  The carrier assembly bolts to the front of the differential housing.  To remove the axles, he'll have to unbolt the retainer flanges on the axle tubes and use a slide hammer to pop the axles out. 

While each car is different, our 105K-mile 68 Calais was dry at the axle seals when I recently did the brake work on the car.  I'm not touching the seals until I see a leak. 

Gene Beaird,
1968 Calais
1979 Seville
Pearland, Texas
CLC Member No. 29873

dadscad

If you do replace the pinion seal, be sure to follow the shop manual procedure step by step. If you are not familiar with the process, take it to a differential shop and have them do it. Reason being, if the preload on the pinion bearings is not correct, you are likely to have a very noisy one that will eventually fail.
Enjoy The Ride,
David Thomas CLC #14765
1963 Coupe deVille

speach

Thanks guys. On the heading I noted that is was my 68 but yea 66 and 68 are basically the same. It seems to be only leaking at the point of the drive shaft. I was reading my manual today and saw that you basically just need to what I listed below. I freshened up the brakes a while back and everything seems good there, Maybe I should do all that too. It's crazy how one thing leads to ten more just because, you mine as well do it since your there!

1. remove drive shaft
2. remove nut and washer
3. Pull off pinion/ I am going to suck the oil out from the drain hole, at least thats the plan if I can get it off. Past schmucks partially stripped the nut
4. Pull out old seal
5. Clean and install new seal
6. Put back together

Current cars:
1986 Military Chevrolet Diesel G30 Box Van
1968 Conv DeVille
1989 Toyota SpaceCruiser


You cant take your car with you in the end so drive the dang thing.

WilliamTrausch

Gene Beaird

Don't start the job until you get the fill hole plug off.  If you don't, you'll be stuck when you have to refill it after the pinion seal replacement.  I made that mistake once.  I just about didn't get the fill plug out, but that was after the drain plug was already removed.  Panic ensued until I got the proper leverage to remove the way-too-tight fill plug off the diff. 

You'll need an inch-pound torque wrench so you can measure the pinion shaft pre-load.  You have to measure it before, and after the pinion seal R&R.  This is outlined on pages 4-38 through 4-40 of the 68 FSM. 

So I'll add:
1. Remove fill plug in differential
2. Mark the orientation of the drive shaft pinion flange with the pinion flange.  White paint or a couple of chisel marks can accomplish this.
2. remove drive shaft
3. Remove rear wheels and brake drums
4. measure pinion torque pre-load
5. remove nut and washer
6. Pull off pinion/ I am going to suck the oil out from the drain hole, at least thats the plan if I can get it off. Past schmucks partially stripped the nut
7. Pull out old seal
8. Clean and install new seal
9. reinstall pinion flange and nut, occasionally stopping and measuring the pinion torque pre-load as you go.
10. When you get 2-5 inch-pounds more torque pre-load than the before measurement, you're done.
6. Put the rest back together
Gene Beaird,
1968 Calais
1979 Seville
Pearland, Texas
CLC Member No. 29873

speach

What did you use to install the seal. The book is pretty clear about not beating it in, but I don't see why if I used a rubber hammer or was just gentle???

Also is it necessary to remove the brake drums or is that if I want to do the axle seals as well? I am leery about not being able to get the axles out or back in without some special equipment.

Right now this is temporarily on hold so that I can problem solve something els a little bit more urgent.
Current cars:
1986 Military Chevrolet Diesel G30 Box Van
1968 Conv DeVille
1989 Toyota SpaceCruiser


You cant take your car with you in the end so drive the dang thing.

WilliamTrausch

Dave Shepherd

There are tools to install that type of seal but you can use a plastic hammer to evenly tap it into place, hitting side to side.  The axles must be removed to replace the final drive seals.  Unless you are experienced at this type of work and they are not leaking, best to leave it alone.

speach

Thanks, that was what I was hoping I could do to put the seal in. So I don't have to take the rear wheels and breaks off do I? That doesn't seem to make any sense to me, but I could be wrong???
Current cars:
1986 Military Chevrolet Diesel G30 Box Van
1968 Conv DeVille
1989 Toyota SpaceCruiser


You cant take your car with you in the end so drive the dang thing.

WilliamTrausch

Gene Beaird

The FSM says to remove the wheels and brake drums so you aren't measuring the pinion torque with the brake shoes dragging against the drums or having to overcome the mass of the wheels to turn the pinion. 

The axles don't have to come out, just get the drums off.  If the shoes are worn, and not touching the drums unless the brakes are applied, you're okay from that aspect, but will then really need to later adjust the rear brakes properly. 

I usually tap the seals in using a rubber mallet and piece of 2X4 scrap.  You just want to make sure you don't hit the shoulder on the pinion gear, you could knock it out of place.  Just make sure you're beside the splines for the pinion flange, not in front of them. 

Gene Beaird,
1968 Calais
1979 Seville
Pearland, Texas
CLC Member No. 29873

speach

Current cars:
1986 Military Chevrolet Diesel G30 Box Van
1968 Conv DeVille
1989 Toyota SpaceCruiser


You cant take your car with you in the end so drive the dang thing.

WilliamTrausch

TJ Hopland

For seal installing tools I have had pretty good luck going to home depot and looking around the plumbing department for PVC bits.  I have always been able to find a cap or coupling or combination of adapters that has almost fit perfectly in the housing and over the seal.  Best part is they are cheap.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

speach

Current cars:
1986 Military Chevrolet Diesel G30 Box Van
1968 Conv DeVille
1989 Toyota SpaceCruiser


You cant take your car with you in the end so drive the dang thing.

WilliamTrausch

DeVille68

Hi guys

This thread is already old but I thought my question belongs to this thread.

So, where can I find the "special lubricant provided by the Cadillac Parts Department to assure the satisfactory operation of this unit." (citation service manual)

I need new gear oil for my 68 controlled differential (limited slip)

Thanks
Nicolas
1968 Cadillac DeVille Convertible (silver pine green)