84C47755 wrote:
Gotcha! So really, rotating the gears is the important part. If I have the rear end up on jack stands and run it in gear with the wheels off the ground, would that accomplish the same thing?

Notorious wrote:
Quote:

84C47755 wrote:
Gotcha! So really, rotating the gears is the important part. If I have the rear end up on jack stands and run it in gear with the wheels off the ground, would that accomplish the same thing?

It will to some extent but it will take an eternity to get any serious heat into the oil because nothing is under load. You'll see racers do this in the pits occasionally to warm the oil. And while it's better than nothing, it's not as good as a real run to bring your oil up to temp. Consider adding a real drain plug to your differential. It's a simple mod and only requires locating it properly. Although I've done this on both D36 and D44 differentials while they were out of the vehicle, I only have the locating dimensions recorded for the D44.
Manufacturers should be painfully castrated for not having proper drain plugs in place to begin with.....

Use care when drilling to avoid nicking the ring gear, a depth "stop" on your drill bit at 1 inch will prevent damage. I have used tape wrapped thick enough to make a shoulder or spot weld a washer on the drill bit.

84C47755 wrote:
I wasn't under the impression that removing the rear diff from a C4 was easy. Can you give me a ball park idea of what needs to be done to remove the diff from the car?

84C47755 wrote:
I wasn't under the impression that removing the rear diff from a C4 was easy. Can you give me a ball park idea of what needs to be done to remove the diff from the car?

toptechx6 wrote:
Quote:

84C47755 wrote:
I wasn't under the impression that removing the rear diff from a C4 was easy. Can you give me a ball park idea of what needs to be done to remove the diff from the car?

Removal isn't that tough but I wouldn't do it just to install the drain, not that hard to do it in the car and steel_blue_91 had a great suggestion to use the fuel line as a drill stop. You need to remove the exhaust, rear spring, rear toe link assembly, unbolt the camber bars at the differential and swing them down, unbolt the driveshaft and both half shafts and remove the rear bolts from the support beam, finally the two bolts attaching the batwing to the frame. The assembly then drops out, but you will need to remove the cover bolts to separate the batwing from the pumpkin. I'm sure someone will remind me if I missed anything.

toptechx6 wrote:
Quote:

Notorious wrote:
Quote:

84C47755 wrote:
Gotcha! So really, rotating the gears is the important part. If I have the rear end up on jack stands and run it in gear with the wheels off the ground, would that accomplish the same thing?

It will to some extent but it will take an eternity to get any serious heat into the oil because nothing is under load. You'll see racers do this in the pits occasionally to warm the oil. And while it's better than nothing, it's not as good as a real run to bring your oil up to temp. Consider adding a real drain plug to your differential. It's a simple mod and only requires locating it properly. Although I've done this on both D36 and D44 differentials while they were out of the vehicle, I only have the locating dimensions recorded for the D44.
Manufacturers should be painfully castrated for not having proper drain plugs in place to begin with.....

I agree completely with Notorious on this one, while Andy's procedure in Tech Tips will certainly get the fluid changed, to me the technique is similar to removing engine oil through the dipstick tube, the oil is removed but heavy contaminants including metal and water or coolant remain at the bottom.
There is a good reason for putting drain plugs at the lowest point, it is called gravity! It is not hard to install your own drain plug, as mentioned it is easier when the pumpkin is on the bench but can be done in the vehicle too.
Don't buy one of the expensive "kits" all you need is a long 5/16” drill bit, a 1/8 X 27 pipe tap and a plug the same size as the tap.
Center punch a spot on the pumpkin 1/2 inch left of the lowest cover bolt centerline and 1/2 inch forward of the batwing cover. That dimension should work for D36 or D44. Drill a small pilot hole first before the 5/16" final diameter. Use care when drilling to avoid nicking the ring gear, a depth "stop" on your drill bit at 1 inch will prevent damage. I have used tape wrapped thick enough to make a shoulder or spot weld a washer on the drill bit.
Use an extension and 12 point 1/4" drive socket on the tap to cut the threads if doing this in the car. The draining lubricant will remove any chips.
The 1/8" drain plug seems small but warm lube drains quickly and more thoroughly than any suction gun.

84C47755 wrote:
I wasn't under the impression that removing the rear diff from a C4 was easy. Can you give me a ball park idea of what needs to be done to remove the diff from the car?

CentralCoaster wrote:

I wouldn't bother doing all that, rear diff fluid is about the least critical fluid on the car.

But if you want to, you've gotta pull the exhaust, disconect two half-shaft straps, disconnect the lower camber arms, remove the rear spring, disconnect driveshaft and cbeam, then drop it out. It's not easy, but it's much easier than you'd think. You don't have to pull the rear tires either.