964 - checking front differential fluid

[iamtheari]

I searched and found no answers. How does one check the level of the fluid in the front differential? Be detailed about how to get to the point of checking the level - I'm 100% new to that part of the car. Mine has a seepage from the pinion seal and I want to be sure it hasn't leaked out too much to drive safely before I head down the road in the next few days. (I actually have the new seal, which I ordered from Pelican before I even picked the car up since this was an issue found during my PPI, I just haven't had time to install it. If there is a good how-to on that job, hopefully without removing too much stuff from the car, let me know and I might just do that this weekend instead of bothering to check the fluid!)

And a side note on jacking the car up: How much of a sideways angle from horizontal is it safe to jack the car on one side before putting that side on jack stands and moving to the other one? Or should a person jack up to the lowest level the jack stand allows all around and then lift it further? If so, how (since the jack and jack stands have to share jacking points)?

Thanks, guys. Looking forward to a nice mid-winter road trip with some more confidence in that front differential. (It's for work but why let that get in the way of enjoying a few hundred miles in a 911?)

[iamtheari]

Well, no responses yet, but I'm planning to at least poke around at it this weekend so I don't spend the entire time in my office. I have pages 39-25 through 39-27 of the workshop manual (the procedure for "Removing and installing front-axle final drive"), pages 39-31 through 39-35 ("Disassembling and assembling front-axle final drive"), and a Rennlist forum post on changing the fluid (Rennlist Discussion Forums - View Single Post - C4 maintenance and upgrades) handy. I have 2 qt. of Royal Purple 75W-90, new plugs for both fill and drain, and new crush washers for both. I have a good attitude. But I am still hoping for a little guidance before I get started as this is the first time I'll have worked on the front end of my car at all.

I've decided that checking the fluid is dumb. It's either low from leaking or not, but either way it's old. So my plan of attack is to get under the car, get the aero cover off, and inspect things. Goal: Replace input shaft seal without removing steering rack or differential. If that appears to be impossible, then instead I'll drain and fill and do the seal later on when I get around to rebuilding the leaky steering rack.

I will pick up some hose to help get it the fluid in--I need a new fuel hose for my lawn mower, anyhow, so I'll get that while I'm at it. I will also pick up some appropriate grease for installation of the seal if I end up doing that. My main concerns, in order going through the procedures and not in order of importance, right now are:

1. Removal of front-axle final drive includes disconnecting a joint in the steering shaft. Will I need to do anything special to avoid my steering wheel being off-center when I'm done?
2. Unclipping power steering lines from holder. Is this a disconnection of the steering lines, and if so what's the best way to avoid power steering fluid in my face?
3. Undoing transmission-bearing screw and front-axle cross and side members to drop front axle. Will I need to support it, drop it on my chest, or just let it hang?
4. MAIN question: Undoing drive shaft at flange from front-axle final drive. This is where I think I can maybe get access to the input shaft seal on the differential housing. Is this possible without doing the preceding steps?
5. Do I need a new rubber seal on the facing surface of the central shaft if I did not disassemble that portion of the assembly?
6. Do I need any special tools to remove the old input shaft seal or to install the new one? ("Special" includes anything right down to a particular-size metric socket to tap it in with, if necessary.)
7. What kind of grease is recommended for installing the seal? The manual says "Olista Longtime 3 EP" - is there an equivalent I might be able to find in my small-town hardware store or auto parts stores, or at least information on specs so I can shop for an equivalent?
8. The notes on disassembling say to remove the lock nut with a pair of special tools. The exploded drawing shows the lock nut sitting over a bearing race, with two screws apparently screwed into the lock nut itself, and the seal sitting on top of those. Do I need any special tools before I attack this job?

Thanks for any and all responses. I have high hopes that I'll be on the road Monday morning with one less leak on my car.

By the way, since I can't find much information on these tasks, I will try to borrow a camera and take pictures as I go. That way I can more readily ask for help if I screw things up but also, in the event that I don't mess anything up, I can write up a how-to and actually contribute something back to this fine online community.

[iamtheari]

Update: After removing the front and tunnel aero covers, I was able to observe that disconnecting the center shaft from the front differential and replacing the input seal on the front differential would be nearly impossible with the differential in the car. Removing it looks like it would be a lot easier after removal of the steering rack. I am planning to put new seals on the steering rack in the not-too-distant future, anyhow. So I will just be changing the fluid for now (I'm letting it drain overnight and all day today since it was cold and so was I). The seal replacement will wait and I will just keep cardboard under the front end of the car for a few more months.

[PNine64]

I have a C2 and can't really help on the fron diff questions. There are lots of ways to skin the cat when it comes to jacking the car though. I get a little nervous when I jack up one side too high. I've driven the fronts on wood blocks or ramps. Although I haven't tried it yet, next time I'll probably jack the motor and get the rear stands in place...then use a wide piece of wood in the front and jack that up (putting stands in the front). Cactus put something on the Rennlist 993 section on this a while back. Speaking of Rennlist...there's probably a good chance that you might get some good feedback on your diff over there too.

[Newsboy]

If you remove the steering rack, remember to order 4 new bolts of the proper grade. Make sure your wheels are pointed perfectly straight ahead when you remove & re install the shaft coupling. If you take accurate measurements prior to removal, you can put it back together without an alignment.

[BenBgood]

My car is actually in the shop having this done, I'll see about asking the mechanic for any tips he has on the job...might be a week or so before I get down to the shop though...

[iamtheari]

BenBgood: Having the seal done? I'd love to hear what they have to say. The only person I've talked to about it was the shop that did my PPI on the car and an unbiased opinion would be great. Thanks for the offer.

[BenBgood]

I just talked to the shop manager breifly over the phone, he suggests it is very difficult to do with the differential in the car, but quiet quick once removed. I am hopeing to pick up my car this week or next (we're doing a lot more than just this seal...still trying to dial it in on the dyno), when I do I'll talk to the mechanic who did the work...

[iamtheari]

Excellent. What are you doing to the car other than that seal? I'm all ears for ideas on mine.

[BenBgood]

Just finishing up a 4.0L MAF converted Engine, Suspention and Brakes ;-)...my wife thinks I'm just looking for ways to burn up money though ;-o