rear diff fluid change, 86

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Aug 2, 2008 | 11:13 AM

NewbeeBob

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rear diff fluid change, 86

My 86 project comingn along nicely. replaced steering rack, steering column, repaired cluster, new exhaust, new cat converter, new hood cables. Went for a ride for the first time.

As messed up as the engine is, this thing is still fast!!

time to turn to the engine. doing all the usual stuff, wires, cap, roter, plugs, belt, break pads, maybe rotors, rebuild throttle body, etc. And I'm replacing all fluids, which brings me to the rear end.

I don't see a drain plug, haven't looked at the manual yet, kind of scared what it will say. What's the best way to drain and refill the rear diff? I thought I read in the 101 projects for you c4 book that there was a kit you buy so you could drill a hole in the diff tap some threads and insert a threaded plug. Anyone heard of this or install one?

Thanks folks

Aug 2, 2008 | 11:27 AM

pmihaltian

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From: Charlotte NC

You have to use a hand pump to suck the gear oil out of the differential case. Here are the proper instructions complete with photos. You can get the hand pump at SEARS for about $12.

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Changing C4 Differential Fluid.pdf (282.3 KB, 438 views)

Aug 2, 2008 | 02:02 PM

toptechx6

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From: FL

Quote:

Originally Posted by pmihaltian

You have to use a hand pump to suck the gear oil out of the differential case. Here are the proper instructions complete with photos. You can get the hand pump at SEARS for about $12.

Or install a drain plug, but don't buy one of the expensive "kits" all you need is a 5/16” drill bit, a 1/8 X 27 pipe tap and a plug the same size.
Center punch a spot 1/2 inch left of the lowest bolt centerline and 1/2 inch forward of the batwing cover. Use care when drilling to avoid nicking the ring gear, a depth "stop" on your drill at about 1 inch will work. (Slide a length of rubber tubing on the drill bit cut to the correct length.)
If you are installing the drain plug with the differential in the car it helps to have a long 5/16” drill bit, use a ¼ drive 12 point socket with extension to turn the tap. The draining lubricant will remove any chips.

Aug 2, 2008 | 11:27 PM

vinnies87

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From: Magnolia Mississippi

St. Jude '03-'04-'05-'06-'07

Guru tech tip works great, but i modded it by adding a fine wire coathanger to the tube going into the diff, allowing to get to the bottom and move it around to get all.
Personal note, When i installed my drain plug, I i did an extra drain and flush to make sure there were no metal shavings.

Aug 2, 2008 | 11:36 PM

nate23

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Here's what I did: remove exhaust, remove driveshaft and halfshafts, remove c-frame, remove rear tie rods and camber rod, remove batwing and diff then took everything to the parts washers and made wife clean for 2 hours. Then I replaced all the ujoints and reassembled. All to get fresh new royal purple and some stinky limited slip additive in the diff.

I get a little crazy like that sometimes. In for a dime, in for a dollar.

Seriously, why couldn't they put a drainpkug on the diff?

Aug 3, 2008 | 03:21 AM

pmihaltian

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From: Charlotte NC

Quote:

Originally Posted by nate23

Seriously, why couldn't they put a drainpkug on the diff?

Good question. I think they did in later C4 years.

Aug 4, 2008 | 11:51 AM

NewbeeBob

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Thanks folks

Thanks folks;

I think for now I'll do the pump method. I think I have a pump leftover from my now sold boat. I like the drain plug installation idea though. I'll revisit in the winter when wife lets me play in the garage longer.

Thanks again.