Diif plug and fluid change.

[Mad4slalom]

Just completed installation of a diff drain plug ,( thank you gavin, (emc) for the talk through advice) and changed the diff oil and additive. A bit fiddly , a bit messy but a good mod. I drilled and lock wired the plug as a safeguard for extra peace of mind. (Not in this pic )Off to do some figure of eights in a car park to get the fluid where it needs to be next. Also I got some grease into the clutch cross shaft and seems to have stopped the movement , need to see if it is quieter while driving now.

 

[CaptainK]

Any chance of you / EMC doing a write up of this mod in the newsletter or the forum?

 

[Mad4slalom]

Any chance of you / EMC doing a write up of this mod in the newsletter or the forum?

Gavin suggested to drill a Pilot hole up through the centre of the strut rod bracket and right through into the diff. Make sure you have a container ready ! I thought I would get through the bracket then the dif, they must be touching as when I broke through I realised I had gone through both as oil started coming out. ( I put some grease on the drill bit to catch any swarf) when the oil has all drained the next thing to do is enlarge the pilot hole in the bracket Only, using a 1” hole saw. ( Be very careful here only to enlarge the hole in the bracket) de burgh the edges.
Once the bracket hole is clear, step by step enlarge the pilot hole in the diff casing up to the11.8mm tapping size drill. Now take your 1/4 Bsp t(taper) tap. I couldnt use a tap holder due to the exhausts so found a socket that fitted the square shaft of the tap. It took a while for the tap to start to bite as the tap is very fine at the tip. It finally started to cut , again, I put some grease on the tap to catch swarf or chips of diff casing.
Trickiest part was keeping the tap going up straight as you are working arms up in the air and very achey. Half turn forward , quarter turn back. Due to the thin case of the diff you are only cutting one or two threads, the ta then stops cutting and just runs up through the thread into the diff. This is as much as you can do.,
I then wiggled a magnectic screwdriver around in the hole and picked up a few more metal chips. I then flushed a pint of ordinary gearbox oil through to flush out any other debris.
I left it overnight to fully drain and then re filled with the correct ac delco oil and additive. I put in one quart of oil then added the additive then topped up with the other quart of oil until it just ran out of the fill plug. It looked to have sealed but notice one drip had formed overnight. I was very cautious not to over tighten due to the few number of threads. I tightened a bit more , checked next day, one drip , re tightened and seemed drip free. Ibthen took car to a car park and drove several slow figure of eights as I read that this would dstribute the oil and additive throughout the plates of the posi drive.
Next morning ,… One Drip !! ffs so back on the ramp, drained the diff , ( a doddle with the new plug) caught and saved every drop of the 95 quid amber nectar. Added a copper crush washer and some ptfe tape to the plug. Tightened up tighter than before , re filled it and it finally seems drip free.
So to run through requirements ,
You will need ,
A 1/4 inch bspt plug ideally allen headed but mine had a 16mm hex head.
A pilot drill aprox 1/4 inch.
I hole saw approx 1 inch.
A 1/4 bspt tap (taper, not parallel) .
An 11.6 or 11.8 drill (tapping size) for bsp tap and a few drills between that and the pilot drill to open up the pilot hole ready to tap . . Hope this explains in detail. Good luck.

 

[teamzr1]

FYI,
If ever wanting a drain that never needs to be taken in or out, I have used these
The bolt end is hollow
the drain side is spring-loaded to prevent it from popping open, plus it has a latch where the drain side is pushed inward
and then turn it to the latch stop
With the spring-loaded against the latch it will not pop open and wanting to drain push drain side inward, turn and let
go and drain opens to flow




For my 1999 C5 Diff, and also tranny, I replaced the fill and drain plugs with fittings that have hose inlets
Then ran a hose to each and other ends meet with a tee drain that opens and close
The fill side I used a clear fuel filter mounted right after the fill hole as that lets me know if the diff or tranny is full when putting in new fluids

This is mounted right by the rear fascia, so I do not even have to lift the car to change fluids
So wanting to drain so to drain I just open the petcocks to a drain can

To fill I use a container for new fluid volume, with a small electric pump via petcock to pump in

 

[teamzr1]

And if you want to go a step further like I did in my 99 C5
This is a dual split coolers.
It has 2 inlets and 2 outlets, so can be used to cool tranny and rear diff or can daisy-chain them to make one larger cooler
Each has its own pump which is thermal controlled and then one fan to cool both coils

 

[CaptainK]

That is an awesome write-up thanks Mad. Good job . Far braver than me.