Hello, I understand that this is quite a common fault with C5's. But it would appear that this may be slightly different to one's that I have seen posted before. Last year I noticed a small leak coming from the driver's side of the diff. The side plate on the diff housing is held in place with a number of small screws, it appeared to be leaking from the bottom screw. I cleaned the area up and checked the oil level-which appeared to be ok. Tried the obvious first by checking to see if the screws were tight- they were. Now here is the strange part- it only appears to leak if the weather is hot ( not very often in the uk these days), and the vette has been driven for 20-30 miles(or more).It almost implies that the oil is thining with the increased temperatures, all over autumn/winter/spring it has not leaked at all- so much so that I had forgot all about it. Until yesterday, when it leaked again.What would be your suggestions-please bear in mind that the only Corvette dealers are specialists-we cannot take it down to our local GM dealership. p.s.If I don't get back to you immediately-it's because I work 12 hour shifts. Thanks.

 

it is a common problem. The fix is labour intensive as it requires removal of the rear suspension. the O ring usually is replaced anc RTV used to aid in sealing...

this from the C5 tech tips...
Leaky butt
The differential can leak from the side covers. The problem has to do with the design. The lip on the casing is not wide enough to create a proper seal with the cover. Resealing the covers can be successful, but many dealers do not use the correct sealant.

I'm sure that I have seen a DIY repair How to ... here on the forum

 

I'm getting ready to do mine. The dealership tried 3 times to fix it. I will never go back to a dealership. I'm doing it myself so I know it's done correctly. It seems like if it's just leaking around the cover all you need to do is to remove the old sealant and replace it new stuff. Part number 1052943. It comes in a red 1.69 FL. OZ. or (50mL) tube. While you're there you should replace the seal as well. Part number 88996703. There are posts about replacing the seal but none of removing the cover.

Vehicle: All Technical Service Bulletins Drivetrain - Rear Differential Fluid Leak

Bulletin No.: 03-04-20-006 Date: November 18, 2003 TECHNICAL
Subject:Fluid Leak at Rear Axle (Replace Left Differential Side Cover 0-Ring and Left Axle Shaft Seal, Add Sealant to Side Cover Flange)

Models:1997-2004 Chevrolet Corvette

Condition: Some customers may comment on fluid leaking from the rear axle.

Correction: Verify that the fluid leak is rear axle fluid, not transmission fluid. Replace the left differential side cover 0-ring and left axle shaft seal. Engineering has recommended that sealant be applied to the side cover prior to installation. Use the appropriate service procedure and part numbers listed below.

Service Procedure (Corvette)
1. Raise and support the vehicle.
2. Remove the left rear tire and wheel assembly.
3. Install J 33432-A Transverse Spring Compressor to the rear transverse spring and compress the spring.
4. Disconnect the electrical connector from the left wheel speed sensor.
5. Disconnect the electronic suspension control (ESC) position sensor link, if equipped.
6. Disconnect the shock absorber solenoid electrical connector, if equipped.
7. Remove the outer tie rod end nut
8. Disconnect the outer tie rod end stud from the rear suspension knuckle.
9. Disconnect the park brake cable from the park brake apply lever and bracket.
10. Remove the bolts securing the upper control arms to the frame.
11. Remove the spindle nut retaining the rear wheel axle shaft to the hub.
12. Rotate the suspension knuckle until the axle shaft clears the hub,
13. Release and remove the rear wheel axle shaft from the differential.
14. Remove the left muffler.
15. Drain the rear differential fluid.
16. Remove the retaining bolts and the damper/tuned absorber from the differential.
17. Loosen the nut retaining the transmission to the transmission LH mounting stud.
18. Install a second nut onto the stud.
19. Remove the stud from the differential cover.
20. Clean any dirt or debris from around the differential cover.
21. Remove the bolts retaining the differential cover.
22. Remove the differential cover from the differential.
23. Remove and discard the 0-ring seal and the axle seal from the differential cover.
24. Clean the 0-ring sealing surface on the differential cover and the differential housing.
25. Install new 0-ring, P/N 89047953, to the differential cover.
26. Apply a continuous 3 mm (0.125 in) bead of sealant, P/N 1052942 (Canadian P/N 10953466), or equivalent, to the cover flange.
27. Apply sealant around the bolt holes. Keep sealant away from the 0-ring.
28. Install the differential cover to the differential.
29. Install the differential cover retaining bolts. Tighten Tighten the bolts to 28 N.m (20 Ib ft).
30. Clean the excess sealant from the left cover/housing splitline.
31. Using two nuts installed on the stud, install the transmission mounting stud to the differential cover. Tighten Tighten the stud to 42 N.m (31 Ib ft).
32. Remove the second nut from the transmission mounting stud.
33. Tighten the nut retaining the transmission to the transmission LH mounting stud. Tighten Tighten the nut to 50 N.m (37 Ib ft).
34. Install the damper/tuned absorber and bolts to the differential. Tighten Tighten the bolts to 25 N.m (18 Ib ft).
35. Install the new axle seal, PN 88996703, into the differential cover using J 46405.
36. Install the left muffler.
3 7. Install the rear wheel axle shaft to the differential.
38. Install the spindle nut retaining the rear wheel axle shaft to the hub. Tighten Tighten the spindle nuts to 160 N.m (118 Ib ft).
39. Install the bolts securing the upper control arms to the frame. Tighten Tighten the upper control arm bolts to 110 N.m (81 Ib ft).
40. Connect the park brake cable to the park brake apply lever and bracket.
41. Connect the outer tie rod end stud to the rear suspension knuckle.
42. Install the outer tie rod end nut. Tighten
- Tighten the outer tie rod end nut to 20 N.m (15 Ib ft) to seat the outer tie rod stud.
- Turn the nut additional 160 degrees.
- Check the outer tie rod end nut for a minimum torque of 45 N.m (33 Ib ft).
43. Connect the shock absorber solenoid electrical connector, if equipped.
44. Connect the electronic suspension control (ESC) position sensor link, if equipped.
45. Connect the electrical connector to the left wheel speed sensor.
46. Remove J 33432-A Transverse Spring Compressor from the rear transverse spring.
47. Install the left rear tire and wheel assembly.
48. Refill the rear differential fluid.
49. Lower the vehicle.

 

The leak "evidence" you've described can also be from the vent puking once and awhile. If it "leaks" when it's hot outside, or if you drive the car hard, then it could be coming out the vent.

Check you oil level again. There were some threads a while back that made it sound like the level should be a little below the bottom of the fill hole to help prevent vent leakage. Do a search for more info.

 

I suppose the fix is similar for the pass side...

 

I had exactly the same problem on mine Kevin. Unfortunately the seal is a known waeakness and its a major job to strip it down and replace the seal. Theres a new designed seal that solves the problem. Mine was done under warranty.

Here's the TSB link for you:

http://www.corvetteactioncenter.com/...over+Flange%29

I suspect Bauer Millett or one of the specialists may be your only option unless you're feeling very brave.

 

 

Ok, I’ll add my two ¢ worth. Here is a link to info on what was suggested for my leak. There is a new type o-ring for the cover and the output shaft seal has a new number as well. If you are going to change one, I would suggest changing both the o-ring and the shaft seal on the driver’s side. I also found that I didn’t have to take as much a part to do the job as some of the suggested write-up would have you do.

Per the service bulletin (sorry I don’t have a copy) they tell you NOT to put any sealant on the o-ring or the o-ring area. As far as the cover flange, do use the GM gasket eliminator or in my fix, I used Loctite 515 gasket eliminator. It is very important to ONLY have this sealant on the cover flange to case interface.

One more important step, before reinstalling the output shaft into the differential, be sure to lightly grease the shaft seal and the shaft. This is the only lubricant the shaft to seal see for the first few miles until the differential lube works its way up to this area.
Bottom line, the leak repair wasn’t as bad of a job as I first thought it would be. Total time for me was about 2 ~ 3 hours.

Good luck with the fix,

Eric D