Old Atf Mistery

[G and C Johnstone]

On my old Es 300 I have been concerned by the discolouration of the trans fluid. It was dark. It still spread quickly on paper and the bouquet was still very much that of hydraulic oil.

Having listened to the advice of the learned on these forums I have drained the sump and diff and replaced the filter and gasket. For piece of mind I used new crush washers for the drains. They were aluminium. Replaced the oil and allowed the trans to pump the torque converter oil to waste from the radiator cooler hose. I manage to add 6 litters before there was any sign of aeration in the waste container. At this point I stopped the engine and added another three litters with the engine stopped before running the engine again while adding more. The wasted oil was becoming clear when five litters had been pumped out. I stopped the engine and the adding of oil when my 10 litre waste bottle was full.

I added enough oil to the trans after this so that surely there was plenty in there.

The draining of the diff produced just under a litre of the same black oil that had come out of the sump of the trans.

Error: On my car the differential is within the transmission and can not be refilled to overflow from its filler hole. The overflow is into the main trans housing. The engineering behind allowing the diff to retain an oil supply is probably to limit damage to the differential should there be a major failure. I have seen transmissions that have been carelessly towed too fast too far and the end begins when the bearings that are idling at the back of the gear box give up for lack of lubrication which is dependant on rotation of the front of the gear box.

I dipped the oil and thought that there was some in there. It is quite difficult to establish the true oil level on my car because the dipper tub bends and the dip stick scrapes oil from the tube on the way in and out.

A test run confirmed that no immediate damage had been done. The main driver of the car took it out for a drive and said that it seemed fine and was not making bucking gear changes like it had been. This he quickly qualified by adding that the engine and transmission were properly warmed up for his test and his complaints were of cool engine gear changes.

The car was parked over night and appears to have dropped no oil. The stone cold oil level was spot on. So good that I took a picture of it.

However I will not advise anyone to put about enough oil into a transmission as I did.

It is reported by a worthy general mechanic that the original oil could have been Dexron II which has been known to discolour in quite normal use.

The mechanic said I will not have done any harm by indulging in this excesesive maintenance. His firm has a transfer machine to speed up the type of work I did. He cautioned that the job can be rushed with the machine but that if it is done with care nothing will be blown to bits and new oil is the only result.

I will still have some old oil because of the aeration that occured and some oil will have been laying in the cooler but I hope that the car will be better for having done the flush.

Car is 1996 @ 57K kilometers ex Singapore.