Transmission fluid change.

[Craigguild]

Hey,
This is a little embarrassing, but how does one change the fluid in the transmission?
Is there some kind of plug underneath that can unscrew to drain it? My fluid has a bit of a burnt smell to it, and the gears have been slipping a little.
The box in my car is an automatic transmission.

Regards Craig.

[Dangermouse]

Back the car up onto ramps after warming the engine up.

The transmission sump pan is clearly visible and it had a drain plug. Like the oil plug it is also a square fitting.

Drain the fluid like you would oil. If the tranny is slipping then you would be advised to remove the pan and the filter, which is underneath.

Inspect the bottom of the pan for debris, particularly fibers.

The filter is hard to clean without disassembling it ( there is a thread on here somewhere about that). They are unobtainable new btw.

[DMCMW Dave]

Careful - there are TWO drains on an automatic. The one toward the rear of the car is the differential oil (80W90-weight) and the one on the pan is the gearbox (Dexron III ATF). The fill for the differential is on the side of the differential next to the axle. The fill for the automatic part is the dipstick tube. Don't drain the differential unless you have a way to fill it!

[sdg3205]

Dave - should both the ATF and diff fluids be changed if the last known change is unknown?

We were going to do the ATF, but might as well do the diff if its best.

[DMCMW Dave]

Dave - should both the ATF and diff fluids be changed if the last known change is unknown?

We were going to do the ATF, but might as well do the diff if its best.

My personal belief, is that the ATF should he changed with every other engine oil change, and the diff changed every 30K miles or 10 years. For most DeLorean owners that means the ATF every 2 years and the rear oil every 10.

FWIW factory recommends all fluids at 30K.

[sdg3205]

My personal belief, is that the ATF should he changed with every other engine oil change, and the diff changed every 30K miles or 10 years. For most DeLorean owners that means the ATF every 2 years and the rear oil every 10.

FWIW factory recommends all fluids at 30K.

Thanks Dave!

Can't see a reason not to do it then.

[Jonathan]

Thanks Dave!

Can't see a reason not to do it then.

I take it your next restoration car is an auto?

If you have any questions about changing the ATF or other things you encounter when doing it, let me know. I changed mine this past season and have lots of photos or thoughts if you need clarification on something.

[sdg3205]

I take it your next restoration car is an auto?

If you have any questions about changing the ATF or other things you encounter when doing it, let me know. I changed mine this past season and have lots of photos or thoughts if you need clarification on something.

Jonathan! HELLO! (read like Uncle Leo from Seinfeld)

This is for 3922, yes an auto. It belongs to a new owner out here in BC. We're doing the usual updates. It's a very nice car - I'm trying to not wreck it :)

It was stored with 2 other DeLoreans and a few bricklins for a number of years. Still had all original hoses, tires, ignition etc. My guess is some of the fluids are still original.

Have you changed your diff fluid or disassembled, cleaned and reassembled your filter? I was toying with the idea of removing the filter completely and replacing it with Josh's/DPI's inline filter that runs to the cooling pipe. I've heard some say running it, even clean is a risk and that its better to run without it to ensure lubrication. So I'm open to suggestions.

[Jonathan]

Dave!! Glad you said hello. You still say hello, even if you are busy... :) (or stealing books...)

I had help with changing the rear differential fluid a couple seasons ago. I didn't see much of how it was done, but a couple seasons of gaining knowledge and confidence on these cars and I'll take care of it next time. Mine has leaked from that section of the transmission in the past. It's gear oil, the thin stuff, like you lube the angle drive with. You check level through the upper hole with your finger/eye. Come to think of it, that might be where you add the fluid once you're ready to fill it up again. Better double check that one with someone else. As I understand it, level is important, yet if the leak is at the axle seal where mine was, the drip drip will eventually get down to a point where it will stop once the level is lower than the leak point.

I my ATF was changed a couple seasons into me owning my car when I changed out my shift computer/governor. Last winter though, I had the front end in the air after it was stored (and cold) and came out one morning to see the red ATF all over the place on the floor at the back. Turns out my dipstick tube seal was poor and the extra angle plus the cold temperature on the rubber let it spill out. I wanted to change the fluid anyway, so away I went.

The dipstick tube seal is on the top of the pan sort of. It calls for an o-ring and many folks use two of them. I had the otterstat seal idea as a better alternative, yet I couldn't get the dang thing in there and ended up going with the double o-ring idea afterall. The ATF you fill by pouring it slowly down the dipstick tube from the engine bay.

Since my ATF pan came off while I was figuring out the leak, I put a new/replacement cork seal on. I got a nice up close and personal view of the filter but did not take it off nor apart for a cleaning. Based on the lack of the copper tubing around the edge, I'd say no one before me had taken it off for cleaning either. I have also heard the concerns for the filter limiting the flow of fluid through it with the way it is designed. I won't comment on preferred solutions like you mentioned with running the inline filter and no internal filter as I'm not educated enough on it to make a statement. I do understand the concerns with lack of flow as much as debris but not sure which would be best to pick if you can only have one good and one not so good.

The change out of the ATF is pretty simple overall especially if your pan doesn't come off. I believe the idea is to start the car and let the fluid get warm but not full hot. Then take your pan drain plug out with the tool of your choice (same tool for the oil pan plug on many cars). Drain the fluid completely and reinstall the plug with a new crush washer (same as the ones that go in the oil pan plug). With the car on level ground of course, fill through the dipstick tube 2 quarts (I think, double check that as the non-metric amount confuses me!!) and then start the car and let it warm up. Check the level as you go and add small amounts until you get it to the proper place on the dipstick. Put the gear shifter through the PRND21 a couple times as you're adding the final amounts too.

If this car is new to you you'll likely need the pan to come off just to have a look if nothing else. Non-pan removal ATF change is really simple and Dave's advice about changing every 2 years is really not a big price to pay to ensure you know what is happening in there.

Come to think of it, if you're also going to need to do anything with the shift computer and it's wiring harness, one of those connections is on the inside of the pan area. If the harness comes off, so will the pan to get to it.

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[sdg3205]

The pan is definitely coming off. It leaks from at least two locations at the pan seal. I have a new cork seal replacement.

I'll see what i can dig up on differential fluid replacement.

[Jonathan]

ATF level check question:

How long does it take the auto trans fluid to get up to full operating temperature?

The reason I ask is because when checking my fluid the other day, I noticed it stayed cooler much longer than what the engine temperature was telling me the coolant was doing. I realize the two fluid systems aren't combined, but was curious how far behind it would take the ATF to get hot while the engine coolant would appear to have already gotten hot.

The ATF level checking instructions are to run the car long enough to have your radiator fans come on and off a couple times, put the shifter through the gears while stationary on a level surface with your parking brake on, and then check the level I checked the ATF level prior to my fans coming on (yet the engine temperature gauge was pretty close to where the fans would be coming on soon), and the fluid felt like it wasn't really all that warm when I touched my finger to it on the paper towel or dipstick. I would have assumed it would have been at least warm, but it didn't feel that way.

Maybe the ideal way of checking the level is to go for a decent drive somewhere, and then when you get back, test the ATF level before putting the car away?