How to - What is the Best Way to a change the Transaxle Fluid?

[Ras12]

I am doing some work under my car and decided to change the transaxle fluid. Can someone point me to a “How To...” or post a step by step (photos would be great) on the best procedure to change the transaxle fluid? And to that end what is the best fluid to use? castrol? redline?

Thanks and stay safe.

[Mark D]

I know there was a DIY around here at some point, although it may have been on the old .com site. I've done it before and it's not too difficult.

Best practice is to remove the fill plug before the drain plug so that if for some reason it is stuck and cannot be removed then you won't have already drained all the fluid out. Then you can still drive the car to a shop for help removing the fill plug, etc. Both the fill/drain plugs should have the same square size tool needed as the engine oil drain plug.

After removing the fill plug, remove the drain plug, replace drain plug and fill from the fill hole until the fluid starts dribbling out. I used a small fluid transfer pump like this one which worked relatively fast:
https://www.harborfreight.com/multi-use-transfer-pump-63144.html

These types of hand pumps are also available that screw directly into a gear oil bottle:
https://www.harborfreight.com/gear-oil-and-fluid-pump-61746.html

but those take FOREVER since they pump like .05 oz with every pump, so it takes like a thousand pumps to fill your transmission. Plus they tend to break easily . So overall, not ideal.



For the gear oil itself this thread should be helpful. I just used regular old 80W-90 gear oil. If you decided to go with synthetic stuff just make sure that it's the non-limited slip diff version since apparently that can cause synchro engagement issues when used in a transaxle. I've heard good things about redline MT90.

http://dmctalk.org/showthread.php?542-What-to-use-DeLorean-Manual-transmission-fluid-(MTF)

[Gregadeth]

Both the fill/drain plugs should have the same square size tool needed as the engine oil drain plug.I think the trans plugs are different than the engine oil drain plug (at least on a manual?). This is what the trans fill plug looks like:
63251

[DMCMW Dave]

I think the trans plugs are different than the engine oil drain plug (at least on a manual?). This is what the trans fill plug looks like:
63251

10 mm square on the manual. Avoid using pliers or a crescent wrench if it's tight, you'll just round off the corners. Snap-On actually has the correct socket. PMP410.

The automatic uses the same socket as the engine on all three plugs.

[Ras12]

Thanks. Assuming Autoparts stores are considered “essential businesses” and are open
Tomorrow I will pick up some Redline fluid and try to change it. Will let you know! Thanks Jason

[DMCMW Dave]

Thanks. Assuming Autoparts stores are considered “essential businesses” and are open
Tomorrow I will pick up some Redline fluid and try to change it. Will let you know! Thanks Jason

Don't use Redline fluid. You won't like how it shifts. (I tried it). The recommended Redline fluid is called 75W90NS, but I found that it was too slick for proper operations of the synchros. Stick with plain old non-synthetic 75W90.

[Cone]

First just make sure you have the correct 10mm drain plug socket. I found one on amazon that was $6. I asked Danny at DMC SoCal what fluid they use, and he told me they use MobilubeHD Plus 80w90. It works great in my car. I think I had original stuff in mine till last year!

[Mark D]

I think the trans plugs are different than the engine oil drain plug (at least on a manual?). This is what the trans fill plug looks like:
63251


10 mm square on the manual. Avoid using pliers or a crescent wrench if it's tight, you'll just round off the corners. Snap-On actually has the correct socket. PMP410.

The automatic uses the same socket as the engine on all three plugs.

Ah yeah, my bad. I knew it was square but forgot it was the male type and not the female type like the eng oil drain. It's been a while since I changed it last, probably due to replace the fluid in mine again soon.

[JETS 81 DMC]

First just make sure you have the correct 10mm drain plug socket. I found one on amazon that was $6. I asked Danny at DMC SoCal what fluid they use, and he told me they use MobilubeHD Plus 80w90. It works great in my car. I think I had original stuff in mine till last year!


CTA Tools 2037 Square Head Drain Plug Socket - 10-Millimeter $5 plus shipping on Amazon.

https://www.amazon.com/CTA-Tools-2037-Square-Socket/dp/B00GLWKGDW

[Mark D]

That would be a male socket for a 10mm female plug.

For the female socket needed on the male trans drain/fill plugs I think this is the one he was talking about:

https://www.amazon.com/CTA-Tools-2048-10-Millimeter-Female/dp/B008TOHA6Q/ref=sr_1_1?dchild=1&keywords=10MM+SQUARE+SOCKET&qid=1586286881&s=hi&sr=1-1

[Nicholas R]

That would be a male socket for a 10mm female plug.

For the female socket needed on the male trans drain/fill plugs I think this is the one he was talking about:

https://www.amazon.com/CTA-Tools-2048-10-Millimeter-Female/dp/B008TOHA6Q/ref=sr_1_1?dchild=1&keywords=10MM+SQUARE+SOCKET&qid=1586286881&s=hi&sr=1-1

Buy this.

It's way too cheap not to. I bought one about 7 years ago, and even though this is the only thing I use it for, every time I need it, I'm so glad I have it. I broke a 10mm open ended wrench on my first transmission trying to take the plug out.

[JETS 81 DMC]

That would be a male socket for a 10mm female plug.

For the female socket needed on the male trans drain/fill plugs I think this is the one he was talking about:

https://www.amazon.com/CTA-Tools-2048-10-Millimeter-Female/dp/B008TOHA6Q/ref=sr_1_1?dchild=1&keywords=10MM+SQUARE+SOCKET&qid=1586286881&s=hi&sr=1-1

Thanks Mark, good catch.
I was thinking of the one I have CT-2037 but is for the oil pan drain plug.:blush:
Owe you a couple more :cheers: once this virus problem subsides. Hope all is well with you and family.

[JETS 81 DMC]

Thanks Mark, good catch.
I was thinking of the one I have CT-2037 but is for the oil pan drain plug.:blush:
Owe you a couple more :cheers: once this virus problem subsides. Hope all is well with you and family.

CORRECTION: The one I have is CT-2036 8MM for the oil drain not the 2037 I wrote above.

[DMCMW Dave]

That would be a male socket for a 10mm female plug.

For the female socket needed on the male trans drain/fill plugs I think this is the one he was talking about:

https://www.amazon.com/CTA-Tools-2048-10-Millimeter-Female/dp/B008TOHA6Q/ref=sr_1_1?dchild=1&keywords=10MM+SQUARE+SOCKET&qid=1586286881&s=hi&sr=1-1

Funny - Snap-on gets over $15 for the same tool. Good find.

[Mark D]

Funny - Snap-on gets over $15 for the same tool. Good find.

Don't you mean only 5 monthly installments of $3? :)

I'm surprised it's only $15 actually, that's not too bad for Snap-on.

[Mark D]

Thanks Mark, good catch.
I was thinking of the one I have CT-2037 but is for the oil pan drain plug.:blush:
Owe you a couple more :cheers: once this virus problem subsides. Hope all is well with you and family.

Thanks! Hope you are doing alright too. Once the world is back to normal I'll definitely take you up on that offer. Hopefully the DeLorean isn't already back in winter storage by then...


But yeah, I had to look up the oil drain plug size as well. The previous owner of my car swapped the regular one for a 17mm hex head plug so I never had to buy the 8mm square tool. I hear grinding a 3/8" ratchet a few thousandths works just as well for that one too.

[Ras12]

Don't use Redline fluid. You won't like how it shifts. (I tried it). The recommended Redline fluid is called 75W90NS, but I found that it was too slick for proper operations of the synchros. Stick with plain old non-synthetic 75W90.

I know we have a shortage of toilet paper (who knows why) due to the virus but no non-synthetic 75W90 gear oil??

Checked a few autoparts stores and non-synthetic 75W90 has to be ordered. What brand do you use?

I feel like the guy in the RockAuto commercial now!

If I have to Order it I probably Should just do it online and get the preferred brand too.

Any thoughts?

(Only Non-Synthetic I could find is Valvoline - https://www.oreillyauto.com/detail/b/valvoline-5149/chemicals---fluids-16461/maintenance-chemicals-16867/grease---lube-16582/gear-oil---additives-16905/gear-oil---75w-90-19583/1e1e9866791f/valvoline-conventional-gear-oil-75w-90-1-quart/820/4773307?q=gear+oil+-+75w-90&pos=13)

[DMCMW Dave]

I know we have a shortage of toilet paper (who knows why) due to the virus but no non-synthetic 75W90 gear oil??

(Only Non-Synthetic I could find is Valvoline - https://www.oreillyauto.com/detail/b/valvoline-5149/chemicals---fluids-16461/maintenance-chemicals-16867/grease---lube-16582/gear-oil---additives-16905/gear-oil---75w-90-19583/1e1e9866791f/valvoline-conventional-gear-oil-75w-90-1-quart/820/4773307?q=gear+oil+-+75w-90&pos=13)

Try for 80W90. Not enough difference to matter. I actually prefer the generic (Super Tech) stuff from WalMart.

[Josh]

It is a pin to find conventional 75w90 gear oil. Damn near everything is synthetic. I ended up using the bulk gear oil from a tractor supply. It does concern me as i am not sure of the quality. But i only run it to break in new gears, run synthetic otherwise.

[Ras12]

Try for 80W90. Not enough difference to matter. I actually prefer the generic (Super Tech) stuff from WalMart.

Is this the one you use?

63256

[Nicholas R]

Try for 80W90. Not enough difference to matter. I actually prefer the generic (Super Tech) stuff from WalMart.

Full disclosure, so do I. I may be an outlier, but in the last 6 years or so I've had to drain and refill my transmission four different times, and didn't want to keep paying for the synthetic stuff. I've even got a $60 bottle of Redline Oil 75W-90NS sitting on the shelf that I've never used. I put the supertech in once telling myself it would be for a "break in period" but the transmissions have always shifted great so I've yet to have a reason to use anything else. Several refills later, I'm still running Super Tech.

[David T]

In the world of Lotus, what you use in the transaxle seems to make a very big difference. The Lotus recommended fluid is NLA so not much choice but to try substitutes. RedLine MT-90 seems to be OK for most of us. 85W-90 won't work but it seems just fine in Deloreans. Hard to understand, it is basically the same transaxle. The main problem is how it interacts with the syncros. It has to have just the right amount of slipperiness so it shifts right and it has to have the right lubricity for the differential and can't attack the bronze. The fluids for the differential and the transmission have different, competing requirements. My guess is the ones who have problems with MT-90 (or even 85W-90) probably have worn parts in the shift linkage and/or need a minor adjustment in the linkage.

[Nicholas R]

In the world of Lotus, what you use in the transaxle seems to make a very big difference. The Lotus recommended fluid is NLA so not much choice but to try substitutes. RedLine MT-90 seems to be OK for most of us. 85W-90 won't work but it seems just fine in Deloreans. Hard to understand, it is basically the same transaxle. The main problem is how it interacts with the syncros. It has to have just the right amount of slipperiness so it shifts right and it has to have the right lubricity for the differential and can't attack the bronze. The fluids for the differential and the transmission have different, competing requirements. My guess is the ones who have problems with MT-90 (or even 85W-90) probably have worn parts in the shift linkage and/or need a minor adjustment in the linkage.

I have to wonder how many Lotus owners have actually tried running something less fancy.

[Cone]

That would be a male socket for a 10mm female plug.

For the female socket needed on the male trans drain/fill plugs I think this is the one he was talking about:

https://www.amazon.com/CTA-Tools-2048-10-Millimeter-Female/dp/B008TOHA6Q/ref=sr_1_1?dchild=1&keywords=10MM+SQUARE+SOCKET&qid=1586286881&s=hi&sr=1-1

That’s right Mark, that’s exactly the one I got from Amazon.

Here’s a link to the fluid Danny told me that they use at DMC SOCAL https://www.thelubricantstore.com/mobilube-hd-plus-80w90-12x1

It is for a dozen bottles, but it was cheap so I didn’t really care having enough for a couple changes. I was having an issue with grinding in reverse when the car was warm, this made a big difference to make that go away.

[Ras12]

So I purchased the oil, found a 10mm square female socket and was able to “social distance” myself from my wife and kids.

Excited to begin I took my time, put the socket on the fill plug and it came off relatively easily.

I then moved to drain plug. Previously I sprayed both the fill and the drain plugs with WD40 and Penetrating Oil several days prior.

Needless to say the drain plug won’t budge. See the photos below as I stated rounding off the plug head and stopped.

Any advice on how not loosen the plug?

Thanks

Jason

[WHO1DMC]

Heat usually works. Haven't had to do it myself but others have.


Dave B.

[JETS 81 DMC]

Agreed, heat should work.

What was the brand of the 10mm socket you used?

[Bitsyncmaster]

I have had to weld a nut on the damaged plug. The heat from the welding makes it come off easy. So if you know someone with a MIG welder try to get him to weld on a nut. If you can still grab whats left maybe heat will break it loose.

[Ras12]

How hot? I got it “warm” to the touch but didn't get it cherry red. I have a propane torch maybe I should use that.

I have a Performance Tool - Performance Drain Plug Socket Set - PFM W54287

[JETS 81 DMC]

[QUOTE=Ras12;256348]How hot? I got it “warm” to the touch but didn't get it cherry red. I have a propane torch maybe I should use that.



Yes, use your propane torch. It need to get much hotter than warm to the touch. Heat around the plug in the thread area. You can also tap it with a hammer and spray some more penetrating oil on it when it is still hot and try to remove the plug.

I hope this helps and you succeed. Then replace with a new plug.

[David T]

Beat the socket on ALL the way with a hammer. Use a breaker bar and a cheater pipe and try again. If you can't get it you can drill it out. Heat isn't as effective because it is a taper thread. Welding a nut on is possible and can work if you have access to a welder. You can't really heat it up enough because you do still have oil inside. If you get a new plug try to get a magnetic one. Use teflon tape so this doesn't happen again.

[Ras12]

Ok so with a little PB Blaster and Heat I was able to get the drain plug out. The transaxle case was full but I don’t think this is the correct color of the fluid. Is it supposed to be this dark drown? And it smells like burnt oil!! Also how do I “flush” the transfer case so it is clean when I finally fill it? Thanks.

[Ron]

Looks like non-synthetic gear oil (which it should be, imho). It is supposed to be noticeably thicker than engine oil. Always smells bad, including when new.

If there were no signs of moisture (milky appearing substance/gel), sludge or metal particles in it, especially in the first to come out, just refill it; For GP/SOP, drive it until the case gets hot then drain & fill again.
If it was extremely contaminated, there are solvents and recirculating tools on the market you can use. (Doesn't seem to be the case here).

[Mark D]

That looks pretty normal in color to me as well.

Gear oil always smells horrible. I think it has something to do with the additives they put in for wear protection. Sulfur maybe?

I have the pleasure of smelling it every time I open the trunk in my daily driver. About 9 years ago when I last changed the gear oil in the DeLorean I had drained it into a 5 gal bucket along with the oil from a recent engine oil change. I put the bucket in the trunk of my car and headed to the recycling center drop off.

On the way there I went over some railroad tracks and the bucket toppled over and the cover popped off. That nasty smelling oil soaked through all the trunk carpets and filled up the spare tire well. It also wicked between all the gaps in the sheet metal making it nearly impossible to clean out. Every once in a while I still go back there with some brake cleaner and paper towels and can still pick up oil residue.

On the plus side, there's absolutely no rust back there :)

[Nicholas R]

That looks normal. Gearbox oil has a lot of sulfer in it; its the main thing that gives it the distinct smell. It smells pretty bad, but I find you go nose blind to it after a bit. My wife on the other hand wont even come into the garage if I'm doing anything with gearbox oil.

[02fanatic]

I think the trans plugs are different than the engine oil drain plug (at least on a manual?). This is what the trans fill plug looks like:
63251


Does anyone know what the specs are for the threads on the 5-speed transmission drain plug?

[Josh]

Does anyone know what the specs are for the threads on the 5-speed transmission drain plug?

drain and fill are 1/4" NPT

[JAZ_DMC]

drain and fill are 1/4" NPT

Drain and fill are not 1/4" NPT – both are actually 3/8" NPT. 3/8" 18 NPT to be exact (for anyone who may be looking for the correct size tap).

02fanatic (dad) and I had a tough time finding a clear answer for this question online, so I thought I'd add some keywords here for others who may be Googling for this answer in the future.

DeLorean - transmission - gearbox - 5-speed - drain plug size - thread size - stripped - cross thread - DMC - national pipe thread - taper - tapered - chase threads

[JSzabo]

Is this the type of Gear Oil I need for my manual transmission?

https://www.amazon.com/Lucas-Oil-LUC10043-Quart-Ounces/dp/B000IG5QPK/ref=sr_1_28?crid=2LKWSPMXDO4O0&keywords=fluid%2Bpump%2Bfor%2Bquart%2Bbottles%2B-%2Btransfer%2Bgear%2Boil&qid=1643940497&s=automotive&sprefix=Fluid%2BPump%2Bfor%2Cautomotive%2C70&sr=1-28&th=1

Or should I just go with the Super Tech (Walmart) 80W-90?

[Josh]

Drain and fill are not 1/4" NPT – both are actually 3/8" NPT. 3/8" 18 NPT to be exact (for anyone who may be looking for the correct size tap).

02fanatic (dad) and I had a tough time finding a clear answer for this question online, so I thought I'd add some keywords here for others who may be Googling for this answer in the future.

DeLorean - transmission - gearbox - 5-speed - drain plug size - thread size - stripped - cross thread - DMC - national pipe thread - taper - tapered - chase threads

You made me go out in the cold and measure my spare transaxle in the shed! It is indeed 3/8" NPT

[GS450-Junkie]

Funny - Snap-on gets over $15 for the same tool. Good find.

I'd love to pay $15. They are now $34!