Drivetrain Oil Change for the
AWD Mitsubishi 3000GT/Dodge Stealth

by Jeff Lucius

Recommended lubricants (from the service manuals)
Manual transaxle and transfer case:
        Hypoid Gear Oil, SAE 75W-90 or 75W-85W conforming to API classification GL-4

Rear differential:
        Hypoid Gear Oil API classification GL-5 or higher
        Above -23C (-10F)   SAE 90, 85W-90, 80W-90
        From -34C (-30F) to -23C (-10F)   SAE 80W, 80W-90
        Below -34C (-30F)   SAE 75W

Lubricant capacities (from the service manuals)
Manual transaxle [to bottom of filler hole]:
        FWD:  2.3 L (2.4 qts)
        AWD: 2.4 L (2.5 qts)

Transfer case:
        5-speed: 0.27 L (0.29 qts) [1991-1992: 0.43-0.51 inch (11-13 mm) below the filler hole; 1993+: to bottom of filler hole]
        6-speed: 0.30 L (0.32 qts) [to bottom of filler hole]

Rear differential [to bottom of filler hole]:
        1.1 L (1.16 qts)

Popular lubricant brands
GL-4 Gear oils (transaxle and transfer case): Red Line MT-90/MTL (50/50 or 67/33 mix), BG Synchro Shift II, GM/Pennzoil/Quaker State/Texaco Synchromesh (synchromeshfluid.pdf), Valvoline Synthetic, Mobil 1 synthetic.

GL-5 Gear oils (rear differential): Red Line 75W90, Valvoline Synthetic, Mobil 1 synthetic.

Motor oil for transaxle only (recommended by Jim Rowe at Metric Mechanic): Amsoil 10W-40 fully synthetic

Red Line products can be purchased at some automotive stores, at some of the on-line stores I have listed on my Links page, and at the mail-order dealers Red Line lists at their web site at I have purchased Red Line lubricants online at (Performance Products and Supply, Red Line Synthetic Oil Wholesalers/Retailers, 345 Freeport Rd., Pittsburgh, PA 15215, 412-487-5004). Use the dealer code 675421 to recieve a 10% "club" discount off the listed price of $7.00 per quart. Shipping (FedEx Ground, PA to CO) was only $8.36 for 12 quarts. I have reproduced the Red Line technical brochures on these products at the following links.
MTL & MT-90 Technical Information
Gear Oil Technical Information

After using Red Line oil in the transaxle for two years and about 8,000 miles, I drained the oil from the transaxle and replaced it with Pennzoil Synchromesh. The used Red Line oil looked satisfactory: it still had a reddish brown color and that "Red Line" smell. There was a small amount of metal particles on the magnetic drain plug. The rear differential and transfer case oils were changed before when the transaxle oil was changed. The oil in both of these cases looked like new and were at the correct levels; I left these cases alone. After switching to Pennzoil Synchromesh, I found the shifting to be improved in the transaxle. My web page below has more information about Pennzoil Synchromesh.

Changing the oil
The 1992-1996 3000GT Service Manual recommends changing the gear oil every 30,000 miles (48,000 km) under severe usage. I think this is a good recommendation under any usage for our AWD cars. To change the oil in any of the gear boxes (if you are doing one you might as well do them all), you will need to lift the car or have access to a pit. I have instructions for lifting and supporting our cars at this link 2-raisecar.htm. Preferably, you want the car sitting level. You will need the following tools: 17-mm wrench and 17-mm socket with ratchet and extensions (trany and transfer case), 24-mm (or 15/16") socket and ratchet (rear diff), torque wrench, two fluid pumps (the Valvoline model shown below cost $3.99 at Checker Auto Parts), a container to catch drained fluid, and either a breaker bar or extension for the ratchet handle. The "gasket", or metal o-rings, used on the drain and fill plugs are not the compressible type. So you probably do not have to replace them. Dealers often do not stock these gaskets, so plan ahead if you want to use new ones. Be sure to dispose of the used gear oil properly. Many auto parts stores will recycle the oil for you for free.

I suggest using two fluid pumps to add oil; one for the GL-5 oil for the rear differential, and one for the GL-4 oil for the transaxle and transfer case. You could of course use one pump and clean it between uses. It is probably not a good idea to "contaminate" the GL-4 oil with GL-5 oil compounds. I store each pump inside marked heavy-duty plastic bags for future use.

Valvoline Fluid Lubricant Pump part no. 818

For the transaxle and transfer case, I used a 50/50 mixture of Red Line MT-90 and MTL gear oils. MT-90 is 75W90 GL-4 and MTL is 75W-80W GL-4. I talked to Red Line about why they recommend a mixture of MTL and MT-90 for our gear boxes. They said that MTL and MT-90 are essentially the same product with different viscosity ratings. Because Mitusbishi recommends 75W-85W weight GL-4 for our transaxle and transfer cases, adding some MTL to MT-90 provides a lower-viscosity mixture than straight MT-90. A 50/50 mixture is not required; two parts of one and one part of the other is satisfactory. You could also just use MTL or MT-90. I used a clean 1/2-gallon glass jar to mix the two oils together, then returned the oil to the original containers that were remarked to reflect the mixture ratio.

For 1993 and newer models, all cases are filled to the bottom of the filler plug or level check plug opening and exact volume measurements are not required if the car is sitting level. For 1991 to 1992 transfer cases only, the fluid is filled to about 1/2-inch below the filler plug opening (0.27 L or 0.29 qts). If a graduated beaker is not handy, you can use common kitchen measuring devices. One cup equals 0.25 quart. One cup also equals 0.24 L (240 ml). One teaspoon equals 0.005 L (5 ml). One tablespoon equals 0.015 L (15 ml). So one cup plus two tablespoons will measure out 270 ml or 0.27 L, just what you need to put in the 1991-1992 transfer case.

Mixing MTL and MT-90

Transaxle and transfer case drain and filler plugs     Transaxle and transfer case fill levels

6-speed transfer case

Transfer case
Loosen the fill plug first. Position your container to catch the fluid (I add some cardboard and newspaper on the floor also), then remove the drain plug. Remove the fill plug. While the oil is draining, clean off the drain plug. There is a magnet in its center that collects metal shavings and particles. After the oil has drained out, replace the drain plug (tighten to 22-25 ft-lb or 30-35 Nm). Use a fluid pump or similar method to add the new gear oil. For 1991-1992 models, I use the transfer case oil level tool I made out of a thin copper strip (pictured below) to check the fluid level. For 1993 5-speed models, remove the oil level check plug on the side of the transfer case. Add fluid till it starts to dribble out the oil level check hole. For 6-speed models, add fluid till it starts to dribble out the fill-plug hole. Be sure the car is level when checking the fluid level. Replace the fill plug (tighten to 18-22 ft-lb or 25-30 Nm), and the level check plug for 1993 5-speed models. Clean the case around the plugs to make it easier to check for oil leaks.

1993+ Transfer case oil level check plug

Transfer case drian plug
Adding fluid to the transfer case
Transfer case oil level tool

The transaxle drain plug is located in the front right wheel well. Remove the wheel for easy access. Loosen the fill plug. Position your container to catch the fluid, then remove the drain plug. Remove the fill plug to allow better fluid flow. While the oil is draining, clean off the magnetic drain plug. After the oil has drained out, replace the drain plug (tighten to 22-25 ft-lb or 30-35 Nm). Use a fluid pump or similar method to add the new gear oil. Add fluid till it starts to dribble out the opening (be sure the car is level). Replace the fill plug (tighten to 18-22 ft-lb or 25-30 Nm). Clean the case around the plugs to make it easier to check for oil leaks.

Transaxle drain plug

Adding oil to the transaxle 2     Adding oil to the transaxle 2

Rear differential
The plugs on the rear differential require a 24-mm or 15/16" socket. Loosen the fill plug. Position your container to catch the fluid, then remove the drain plug. Remove the fill plug to allow better fluid flow. While the oil is draining, clean off the magnetic drain plug. After the oil has drained out, replace the drain plug (tighten to 43-51 ft-lb or 60-70 Nm). Use a fluid pump or similar method to add the new gear oil. Add fluid till it starts to dribble out the opening (be sure the car is level). Replace the fill plug (tighten to 36 ft-lb or 50 Nm). Clean the case around the plugs to make it easier to check for oil leaks.

Rear differential drain and filler plugs     Adding oil to the rear differential

I have heard much good and not any bad about Red Line synthetic oil products. Many people report improved and smoother shifting after switching to Red Line gear oil in the transaxle. I did not notice much difference with my 1992 Stealth. But this may be because I had BG Synchro Shift in there before, another popular gear oil. However, I did notice a very dramatic improvement in shifting in my 1987 Mitsubishi Pickup after switching to Red Line gear oil.

Below is a letter that Chris Radley wrote to Red Line (also posted at their site). I thank Chris for allowing me to post his letter here. If you have a testimonial you would like to share regarding your experience with gear lubricants in our drivetrains, please email me at

Chris Radley
465 Diamond Crest Court
Christiansburg, VA 24073-5887
December 28, 1999

Red Line Synthetic Oil Corporation
6100 Egret Ct.
Benicia, CA 94510

Attention: Dave Granquist
Dear Mr. Granquist:

I wanted to send you a letter describing the terrific results I have obtained using Red Line products. I purchased a 1994 Mitsubishi 3000 GT VR4 in July of 1999. I had always wanted one of these all wheel drive, 4 wheel steering, and twin turbocharged V6 cars. The one I found had low mileage and was in excellent condition. I wanted to be sure I was maintaining it with the best products possible. After doing some research I settled on Red Line as the best choice for fluids.

In September I changed the oil to Red Line 10W30, the transmission and transfer case to a 50/50 blend of Red Line MTL/MT-90, the differential oil to Red Line 75W90 Gear Oil and I added Water Wetter to the cooling system. At this time I was having other work done on the car (tune-up, filter changes, etc.) and the mechanics reported that the intake ports were fouled. They recommended I try Red Line S1-1 Complete Fuel System Cleaner as a first step to clearing up the problem. Here are my results:

  • I had a bottle of Red Line Sl-2 Injector and Valve Detergent so I put this in and ordered a case of Sl-1. I added the SI-1 at my next fill up. I ran this tank of gas and then took the car back to the mechanic. The check of the intake ports showed they were completely clean. Everything else in the fuel and injection system looked great too. l'm glad I bought a case of SI-1 because now I use it regularly at the maintenance dose. The results here were just great.

  • One disconcerting thing about this car when I bought it was the shifting feel. It is often referred to as "notchy". This is the awkward feeling that you can't smoothly transition from one gear to another. I also found that downshifting could be difficult, particularly from 4 th to 3 rd . Most people say that this is just the nature of the all wheel drive, six speed transmission. When the transmission/transfer case fluid was changed there was a very slight improvement in shifting ease. After about 1000 miles the improvement became quite noticeable and by 2000 miles the shifting was virtually perfect, as good as any sports/performance car I have ever owned. I had a chance to compare shifting ease with my brother in laws brand new BMW, and my car is now better. He drove the car and said it shifts better than his 1998 Porsche Boxster. I consider the results phenomenal given that this is an all wheel drive car.

  • Since adding Water Wetter I've noticed that the engine temperature reading holds rock steady regardless of the type of driving I do. Neither stop and go or sustained high speed driving will result in any change in engine temperature. Once the temperature rises from a cold start to a stable reading it just stays there. Consider how remarkable this stability is in light of the fact that this engine supports two turbochargers and even when pushed hard (sustained boost pressure over extended run intervals) it stays put.

  • I can't say that the Red Line engine oil and/or gear oil has done anything obvious for me. At the same time l'm so pleased with the results from your other products that I feel much better using Red Line whenever and wherever I can. I'll be changing the power steering fluid to Red Line at my next planned service.

Please accept my thanks for making great products. Also, please accept my thanks for your prompt and personal e-mail replies on my questions concerning which products to use, change intervals and your general advice.

I am very impressed with Red Line products and service. I am definitely a devoted user and vocal proponent of Red Line. From my point of view no one who owns a performance car should even think of using anything else.

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Page last updated December 14, 2003.