Changing Sierra Differential Oil

[Wrightpayne]

Couple of years ago had a quaiffe ATB rebuilt into a 3.62 diff supplied by SPC. It has always been noisy compared to my 3.9 so after a conversation with an old seven acquaintance, I decided to try some good 'ole Hypoid EP90 Ford oil in it rather than the 75/90 synthetic stuff.

Knowing the diff had no drain plug I wasnt looking forward to the job (taking the diff out isnt a 'fun' task!). Suction is the answer (maybe)!!

Boot Floor

Whilst at my mates, picking up his pela pump, I had a good look at his car which doesn't have a boot floor and everything looks accessible from above.

Back home, boot emptied, floor panels unscrewed and couldn't get it out as all the fuel pipes pass through a hole in the honeycomb. Its late so off to bed. Looked at it again next day and by unscrewing a couple of self tappers under the fuel filler detach the filler neck from the body enough to get the boot floor past without having to disconnect all the pipes/jubilee clips.

Now, free of the fuel pipes the floor is in a position where its wedged and not coming out. Having read posts by Roger Swift et al they had cut out the bit of floor between the back panel and fuel pipes to make removal easy - on mine its hidden by a trim panel anyway. So I squished the honeycomb and cut through with the big tin snips slightly inboard of the finished cut line, so I could saw neatly once off the car. With the floor now notched, I dropped the floor back down to its original position and maneuvered it out (at the third attempt).

 

Removing Oil

At this point I remembered I had a Machine Mart oil syringe I used on my Subaru and thought I'd give it a go.  

From the now completely open boot, plug out, fed the tube in which seemed to hit the diff internals and go down then hit the bottom of the casing. Three goes and 950ml of oil out. I did this whilst the oil was cold which I think helped. I also put a tray under the car first as it did drip / dribble a bit. Success!!

One other point to note is I put some gaffer tape over the edge of the stainless 'rib' that supports the two halves of the floor - its quite sharp and you're working in close proximity to it.

New Oil

Ford have changed the code on the oil to 1781300, which went in easy from above - I could have used the syringe but have an old castrol gear oil bottle saved which I used. (it has an internal pipe so you can force oil upwards if needed). The Ford oil is used in their commercial trucks and 4X4s.

 So, is it any quieter?

Initial drive was quite disappointing in that all the noises were still there, particularly off throttle, decelerating. Then I realised I usually have by ear plugs in. Put them in and the diff does seem quieter than it was before.

So, from a cure perspective, not a complete success, however from a task perspective 100% happy. I had searched the archives and internet but hadn't found a definitive solution to draining the oil easily from a sierra differential. With the boot floor mods I recon a 2 1/2 hour task.

Also spotted the fuel sender gasket and tank breather are showing signs of perishing so will get some attention over winter.  

Regards 

Ian   

 

[Jonathan Kay]

Well done.

At this point I remembered I had a Machine Mart oil syringe I used on my Subaru and thought I'd give it a go.  

From the now completely open boot, plug out, fed the tube in which seemed to hit the diff internals and go down then hit the bottom of the casing. Three goes and 950ml of oil out. I did this whilst the oil was cold which I think helped.

It's usually recommended to do this hot, because the reduced viscosity gives higher flow for a given suck. Why did you choose cold?

Jonathan

PS: It's a lot easier to measure changes in noise objectively nowadays because of apps on smart 'phones.

[Wrightpayne]

Jonathan,

A 50mm dia syringe creates a lot of suck!!

I thought higher viscosity would defy gravity better as removing the oil upwards. Truth be known I had the syringe in hand and was impatient to see if it would work . I did leave it a few mins before the last evacuation to let any oil run down the inner diff walls.

I'd always use the hot method with engines to get the maximum amount of contaminated oil out. I have tried the pela pump on my TDI engine via the dipstick hole but prefer sump plug removal, to be sure you've got it all out.

Good idea re noise meter - hadnt thought to be scientific about the exercise. If I have the diff out to be checked / reset I'll definitely do a before and after db test.

Cheers

Ian