Lotus Elan Central
Changing Your Transaxle Oil

This procedure runs through changing the transaxle (transmission) oil on your Elan. Lotus recommends renewing the oil every 30,000 miles. The original specified oil is "Mobil 1 RTS 9775 fully synthetic SAE 5W/30"--However, the current Lotus recommended oil is "Castrol TAF-X 75W/90". Furthermore, "RedLine MTL" (Manual Transmission Lubricant) is a fully synthetic 70W80 GL-4 gear oil (SAE 5W30/10W30 engine oil viscosity) designed for use in manual transmissions and transaxles. The Transaxle Oil refill capacity is 1.9 US quarts.

So what's with the viscosity number differences? Yes, gear oil has different weight specifications than motor oil; but, in fact, "75W90 gear oil" has the same weight and viscosity properties as "5W30 motor oil"--go figure.

BTW, experience shows you will need exactly a few drops less than 2 quarts, so if you are a pessimist and might spill any you may want to order 3 quarts to be sure you have enough--I order 3 but got away using 2 both times.

The oil should be changed after driving, while it is still warm. This assures the impurities are held in suspension.

Parts / Tools Needed:

  • Socket wrenches (24mm [or 15/16" or 1 inch] and 10mm)
  • Screwdriver
  • Small Funnel
  • 3 ft of small diameter hose
  • 2.0 quarts of transmission oil
  • Penetrating Oil
  • Torque Wrench


The hard part of this procedure is getting the speedo gear screw out !

Just like the oil filter, the speedo gear assembly was located on the car for ease of access--NOT--actually I would like to ask the designers what they were thinking (or smoking perhaps) when they designed the location of this filler hole?! Why not just place a filler hole on the side above the drain hole like all other transmissions?!

The only way to access the speedo gear is to move/remove the coolant reservoir tank as well as the top section of the intake tubing just before the intake manifold. Only after these are removed will you be able to see down to where the speed gear lives. To locate this area look for the speedo cable, which is brownish in color, and follow it down to the top-rear of the transmission. The small bolt and cover plate need to be removed to withdraw the speedo gear assembly!

Important: I recommend accessing the speedo gear first during the procedure. This way if you find you cannot get the speedo gear out you can abort the procedure before draining the old oil!

Accessing Speedo Gear and Draining Old Oil:

  1. Warm up the engine. For best results, warm it up at high RPM on a fun backroad! Actually you want the engine warm but NOT hot as you will be reaching around a lot of metal parts to get to the speedo gear area!
  2. Park car on level ground!
  3. Remove Coolant reservoir tank--Be sure the car has cooled sufficiently before removing the radiator filler cap to avoid boiling water spray! You need a 10mm socket for the tank bolt and a screwdriver to remove the 2 coolant hose clamps on the hoses running to the tank. [Alternatively, you may be able to leave the reservoir hoses in place and just carefully move the tank out of your work area. Be careful because if you remove the bottom hose, the tank coolant will come out!]
    transaxle oil image 1
  4. Next remove the top section of the intake tubing just before the intake manifold--this is the pipe with the bypass valve for those of you so fortunate! [or "upper intercooler pipe"]
  5. Now peer down to where the speedo gear lives (see diagram). To locate this area look for the speedo cable, which is brownish in color, and follow it down to the top-rear of the transmission. Yes it took me a while to find it too! The small bolt (10mm socket) and cover plate need to be loosened and either rotated out of the way to withdraw the speedo gear assembly!
  6. You will likely need penetrating oil on this bolt to help you loosen it! It is a very difficult reach to get at this bolt. There is no real straight access to the bolt and not enough room for a socket wrench to loosen it--believe me I tried EVERYTHING !! You can see below the concoction I finally came up with after an hour or so of trying all else. This gave enough torque, length, and angle to loosen the bolt.
    transaxle oil image 2
    From left to right: flat screwdriver, 3/8" socket extension, 3/8" to 1/2" socket adaptor, 1" socket covering screwdriver head, another flat screwdriver, a dab of my auto detailing clay to hold the screwdriver at slight angle to a final 10mm socket!
    transaxle image 3
    FYI: Others have been able to access this bolt with the use of multiple extension bars and universal joint fittings--just be sure you have the right tools and an 'attack plan' before you get the car apart!!
  7. Carefully loosen the bolt with your fingers once loose, and rotate the cover plate around backwards. Then tighten the bolt down with the plate backwards to keep it in place. Then pull up gently on the speedo gear assembly--it can take a bit of patience to gently break the rubber seal and lift the assembly up. Be very careful not to drop these small parts if you remove them! Rather than removing these parts, you can just rotate the cover plate around, leaving the screw in place, and then remove the speedo gear.
  8. Clean the grit off the gasket and dry the assembly--don't let the dirt get into the tranny hole!

Now you can safely move on to draining the old transaxle oil!

  1. Place catch pan under tranny.
  2. Jack the left front of the car up to allow access to the bottom of the transmission.
  3. Get yourself under the car just enough to remove the drain plug (24mm socket, or 15/16" or 1" socket will work too) from the left hand side of the final drive housing, beneath the output shaft (see illustration).
    transaxle image 4
  4. Frantically reposition the catch pan to where the oil actually goes. It comes out fast through this big hole--so be ready!
  5. Make sure car is then level to drain the oil properly. You may even want to lower it back down to fully drain it.
  6. Allow the oil to drain thoroughly before cleaning and replacing the plug, and tighten to 29 ft-lbs. (39 Nm). There is no washer on this drain plug, so be sure the end seal is clean for refitting.

Adding New Oil:

To check the tranny oil level or to add oil, the speedo gear assembly must be removed, and the oil level indication on the bushing inspected (see top diagram above). Check the oil level with the engine off and the transmission cool enough to touch. The speedo gear is located at the rear of the differential housing and is accessible from above.

  1. Withdraw the speedo driven gear assembly with the cable attached, after releasing the single screw securing the retaining plate.
  2. Add the new oil until the level is midway between the high and low marks on the bushing (about 1.9 qts.).
  3. Replace the speedo gear and be sure to push it firmly down into its proper seating position!
  4. Replace the retaining plate and tighten the bolt to 4.5 ft-lbs. (6Nm).

You will have to fill the tranny up mostly and then fiddle with adding bit by bit of the oil while checking the level frequently between additions.


The biggest problem is coming up with a hose/funnel to put the oil in with. The filler hole is a bit bigger than the girth of your thumb, so your hose can be a decent size but not any bigger than that. Don't go to an automotive store, because all the hose they have there usually is black rubber and has a large amount of insulation--meaning the inner diameter is smaller than you think. Instead go to a hardware/home store that has cheap, thin-walled clear vinyl tubing. Then find a small funnel that will fit the hose you just bought.

Must've been some good ju-ju floating around last night. I hit the garage late last night with the intention of removing everything I would need to get to the tranny plug/speedo cable, spray the bolt with WD-40 and let it sit until today. I'll be if the lil' 10mm guy didn't give it up and come loose without a fuss, so I did the whole thing. I used a 10mm 1/4" drive socket + 1/4" drive flex joint + 6" extension + 3/8" to 1/4" drive adaptor + 6" extension + 3" extension + 3/8" socket wrench to get to the bugger. Whoever suggested to loosen the bolt and plate but not take them out had a good idea. The plate swings out of the way easily to access the gear. Also, Doug, you may want to update the write up to use a 15/16" socket to loosen the drain bolt (actually, whatever the metric equivalent is [24mm] ). The 1" was a bit too big and started to shear the corners of the bolt (it needed assistance from a BFH to come off). And you were right, there is no washer. The drain plug has a small o-ring that just needs to be cleaned. - Dave M

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