Should I start saving for another automatic transmission?

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I've had my D for approximately 2 years now and changed out all the fluids when I purchased it except for the Differential fluid. It had about 32,000miles on it when I got it and I've put approximately another 10,000miles on it since, (its a daily driver). The first year it sat in the driveway while I replaced and restored several systems on it. This past weekend I decided to replace the differential fluid and do some minor fixes that I've been putting off so after jacking the car up and removing the differential drain plug, to my surprise automatic transmission fluid drained out! My question to this forum is how bad is this? The fluid actually looked fresh, red color, not brownish red and the magnet on the drain plug didn't have a large amount of metal filings on it, so do you think I need to be saving up for a new transmission? It runs and sounds fine and after flushing the case out and refilling with the proper gear oil it runs just the same as it did before.

[Gary]

I once had a Ford ranger pickup with a manual transmission. It called for automatic transmission fluid in the case! You would think it would have gear oil in there. I know our Deloreans are not Ford trucks but if a gearbox can handle ATF the differential in a Delorean should be fine. Besides you put gear oil back in and no noise, no harm done?

I think your good to go!

[David T]

I once had a Ford ranger pickup with a manual transmission. It called for automatic transmission fluid in the case! You would think it would have gear oil in there. I know our Deloreans are not Ford trucks but if a gearbox can handle ATF the differential in a Delorean should be fine. Besides you put gear oil back in and no noise, no harm done?

I think your good to go!

It is possible someone changed the fluid and did not know the final drive is supposed to have gear oil in it, not ATF. If you had a leak it would have been overfull with ATF. I would check the level and if necessary drain it to inspect in a while. If the transmission is not slipping and the fluid is clean you should be OK. Very rare for it to leak especially if it has never been touched.

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A leak was what I initially thought about, so I also changed the transmission fluid as well. It was the typical reddish brown color unlike the differential which looked like new ATF fluid. Just thought I'd get some expert opinions, since I'm new to all this. Hopefully no harm done, with fingers crossed, but its been my experience with this car that its never good news.

[Jonathan]

Is there any chance you've misunderstood which one is which? I have never heard of a magnetic drain plug on the differential, only the ATF pan, so that's why I ask. It would also make for a pretty simple explanation if that's the case.

See photo attached.

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[DMCVegas]

I once had a Ford ranger pickup with a manual transmission. It called for automatic transmission fluid in the case! You would think it would have gear oil in there. I know our Deloreans are not Ford trucks but if a gearbox can handle ATF the differential in a Delorean should be fine. Besides you put gear oil back in and no noise, no harm done?

I think your good to go!

Not to get too far off topic here, but there is a difference between the Transmission and the Transfer Case. Some Rangers do require Mercon ATF as the lubricant, but others still require gear oil for the transmission and Mercon for the Transfer Case.

As with the DeLorean and ANY vehicle out there, there are two things to always keep in mind:

Follow the manufactuer's specifications as to what transmission fluid to use. This would also include superceded information about new specs.
Always recognize the differences between various fluid compartments, and know what fluid is supposed to go in where.


That second one is just as important. As with a 4x4 truck, the Transfer Case is completely separate from the Transmission and does require separate fluids.

As Jonathan Pointed out here as well, the DeLorean is no exception to this rule. The front case with the black oil pan is the actual Automatic Transmission gearbox which contains all of the sun & planetary gears that shift around. The rear case is actually the Differential which contains the differential gears (ring, pinion, spiders). The Gearbox and the Differential are two completely separate items that do not share fluids.

[DMCMW Dave]

You may have an internal leak between the ATF part (toward the front of the car) and the Gear Oil part (the differential toward the back of the car/engine). It can go for a long time like this, or not.

Like David said, monitor the two oils. If an internal seal has failed, you'll see that over time the ATF level goes down and the gear oil level goes up and the gear oil turns red. The ATF is much thinner than the gear oil so it's not quite the right lube for the diff, but as long as you aren't stressing it you can go like this for a long time.

At some point you'll need to get it opened up and re-sealed. There are a couple of internal seals that can fail and the outer converter tube can crack.

In the mean time keep the oil full and changed, and if you see the ATF start getting darker change that too. You may go on like this for years.

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Dave I understand your concern here but it was obvious to me that there never was gear oil in the differential case. When I removed the drain plug I expected a slow drain due to the viscosity of the gear oil but it came out like water and closer exam revealed pristine ATF. There was no mixing of the two fluids, as I said I even went as far as draining the transmission fluid just to be sure. I would conjecture that one should be able to tell if mixing had taken place since the two fluids are so different in their viscosity. The differential and transmission drain plugs both have magnets on the end, at least on this car, the biggest problem is finding a suitable adapter to remove them. I had to grind down a perfectly good square socket extension to remove them, oh the pain.

[David T]

Dave I understand your concern here but it was obvious to me that there never was gear oil in the differential case. When I removed the drain plug I expected a slow drain due to the viscosity of the gear oil but it came out like water and closer exam revealed pristine ATF. There was no mixing of the two fluids, as I said I even went as far as draining the transmission fluid just to be sure. I would conjecture that one should be able to tell if mixing had taken place since the two fluids are so different in their viscosity. The differential and transmission drain plugs both have magnets on the end, at least on this car, the biggest problem is finding a suitable adapter to remove them. I had to grind down a perfectly good square socket extension to remove them, oh the pain.

Hot ATF would wash out heavy gear oil. If you have an internal leak you would see the transmission level go down and the final drive go up. At this point I would go with the intentional filling of the final drive with the wrong fluid. In around 1K miles recheck the fluids. If it is leaking the fix is not terrible but it will require removal of the transaxle to replace a few internal seals and maybe a plastic tube. BTW there WAS gear oil originally, ALL the automatics were initially filled with gear oil in the final drives. You must have good, tight seals on your output flanges not to notice a leak with thin ATF fluid!

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OK, so what I gathered so far is that its really not too bad that someone replaced the gear oil in the differential with ATF, which is what I'm assuming and if not, watch for any leaks. As I said earlier, I'll keep my fingers and toes crossed for luck. I seriously need it for this car. Thanks for all the good advice from everyone that replied, in my call of need, you guys rock!