Redline MT-90 Manual Transmission Oil

Introduction

Presumably because the mk2 MR2 has a comparatively long cable-operated gearshift linkage, the shift action is somewhat notchy. In addition, early (1990-1992) mk2 MR2s suffered from fragile synchronizers, giving crunchy shifts in high-mileage cars. Many people on the MR2 Mailing List have reported that replacing the factory-supplied manual transmission oil with one of Redline's synthetic transmission oils improves the shift action and helps to alleviate synchonizer problems in higher-mileage early model units in particular.

I tried Redline MT-90 in my 93T, even though I don't have any gearbox problems and the car had only 35,000 miles on it at the time. I'm happy to report that it did improve the gearshift action. It wasn't a night-and-day difference, but the shift action is now noticeably smoother. I'd recommend this modification.

You probably won't find Redline's products in your local auto parts store. I ordered mine over the Web from Performance Products and Supply. Their service was great and I'd recommend them. If you order through them on their web site you can enter the dealer code ‘675421’ to obtain an extra 10% discount. The total cost for my order after shipping was $28.88 for four quarts. Thanks to PP&S for offering this discount.

Applicability

I have a 1993 Turbo, so these directions are biased toward that particular model. Your vehicle may be different, so please research any possible differences before attempting this procedure. In particular, please check out my Transmission Oil Mysterypage, which contains scans from Toyota's official repair manuals for various model years.

Tools/Parts Required

Four quarts of Redline MT-90. Note that four quarts was enough for my 93T with LSD, since it only takes 4.1 quarts when dry. If you don't have an LSD you might want to buy five quarts, since the BGB says the transmission takes 4.4 quarts when dry.
24mm six-point socket and long-handled ratchet. The transmission drain and fill plugs are probably quite tight, so try to get a six-point socket to avoid rounding the heads.
At least four feet of clear plastic tubing, the largest diameter you can get and still fit it into the transmission fill hole. I would guess about ½-inch outside diameter.
A device from your local auto parts store that screws onto the oil bottle so you can attach the plastic tubing, as shown in Photo 1.
Two new aluminum crush washers from your local Toyota dealer's friendly parts department. The part number is 90430-18008. Please don't try to save a couple of bucks by reusing the old washers.
Oil drain pan with enough capacity for five quarts of the old oil.

Everything that you'll need... Photo 1

Directions

A word of caution: make sure you start this procedure with the engine cold, unless you like the feel of hot gearbox oil burning your hands.

1. Firstly, you need to make sure that you can get the transmission fill plug off before you remove the drain plug. If you remove the drain plug only to find that the fill plug won't budge you'll be stuck with an MR2 with no gearbox oil. So the fill plug comes first. The fill plug is located on the front side of the gearbox casing, as shown in Photo 2. Use the 24mm six-point socket to break it loose. Mine still had a sticker on it saying something like “consult owner’s manual before removing” which I thought was remarkable considering that it had been under the car for eight years.

The location of the drain and fill plugs Photo 2

2. Assuming the fill plug came out without a problem, you now need to remove the drain plug and drain out the old gearbox oil. Jack up the back of the car only if it is necessary, since you'll need it level when you refill the gearbox later. Position your drain pan under the drain plug and remove the plug with the same 24mm socket you used for the fill plug.

3. Wait for the old oil to stop dripping out of the gearbox. I left it for at least an hour at this point.

4. Clean up any spilled oil and find the drain plug that probably fell into the drain pan. Figure out if the old aluminum crush washer is around the drain plug or if it is still attached to the transmission housing. Remove the old crush washer and throw it away. Clean around the drain hole and replace the drain plug, using a new crush washer. The BGB does not specify a torque setting for the drain plug, it merely says “reinstall securely.” General wisdom on the list suggests that 36 ft-lbs is suitable.

5. If you had to jack the rear of the car up in order to drain the old oil, you now need to lower it back down, since it is important for the car to be level for the fill procedure.

6. Drop one end of the clear plastic tube down through the engine compartment in the area of the air filter. If you look under the car you should see it appear somewhere in the region of the gearbox. Grab the end of the tube and insert it into the fill hole. I managed to insert about five or six inches of the tube until I hit anything inside the gearbox.

7. Now attach your oil-bottle device to the tube and pour in the Redline oil. If the tube is quite narrow this will take a long time, which is why I suggested as wide a tube as will fit in the fill hole. Keep pouring in the new oil until it begins to drip out of the fill hole. This is why the BGB refers to this as the “fill/level hole”. See Photo 3.

Filling the transmission Photo 3

8. Remove the plastic tube and replace the fill plug, using a new crush washer. Torque to 36 ft-lbs.

9. Clean up and go for a drive. Check periodically after installation that there are no leaks and that neither plug is working its way loose. Enjoy the nice improvement in shift feel.

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