Ferrari Testarossa Gearbox Oil Change (DIY)

Hello FChatters,

Next up in our how-to/DIY series is a complete list of all the steps we used (and worked for us) to perform a gearbox oil change on our 1987 Ferrari Testarossa. Again, there is a better formatted (with more pictures) version on TrueDriversCar.com/guides.

Overview

It is definitely helpful to have the car lifted enough such that you can get under the middle of the car to reach the drain plugs on the bottom of the pan. Before draining any oil, we opened the two filler plugs - just in case they were seized or if some other issue occurred we wouldn't be stuck with an immobile car. If you have never changed differential oil before, beware that it does contain sulfur which smells quite bad. Having roughly 9L of oil definitely smells bad - it is normal. Before starting, it should be noted that you will need to either have a special 12 mm hex key or modify a 12 mm hex key to be able to fit in the tight space to undue the filler plug. The details of how we modified the 12 mm hex key is shown in step one.

Parts Used (with links)

• 2 x Drain Plug Crush Washers, Ferrai #10265160
• 1-4 oz x Limited Slip Additive,
• ~9.5L of oil**, Mobil-1 75w-90 OR Royal Purple-1 75w-90

* We added some limited slip additive to insure there is no undue stress or extra friction put on the differential given the known issues on the Testarossa. Our experience is that this has worked well, with smooth shifting and excellent corner feel (no skipping, jitters, etc.). The differential on the Testarossa is a highly debated topic with many opinions...
** We use and have good results with Mobil-1 75w-90.

Tools Used (with links)

• Quick Jack BL-5000XL portable lift
• Jack Stands
• Large Oil Pan
• Funnel
• Funnel Hose
• 12 mm Hex Key (Modified) ****
• 10 mm Hex Key Socket, 3/8" Drive
• 42 mm 6-Point Socket, 3/4" Drive
• 12 mm 6-Point Socket, 1/2" Drive
• 1/2" Drive Extension
• 1/2" Drive Ratchet
• 1/2" Drive Torque Wrench
• 1/2" Female to 3/4" Male Drive Adapter
• 3/4" Drive Breaker Bar
• 3/4" Drive Ratchet

*** We purchased the 299 piece socket set from Craftsman a while ago. We became tired of purchasing smaller sets and always missing the socket sizes in between - they get you in an endless loop of buying small sets!
**** This hex key was cut/modified, as described in step one below.
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Procedure Used
1. To remove the filler plug on the oil sump, a 12 mm hex key had to be modified to be small enough to remove the plug without hitting the subframe. This is well documented on FerrariChat.com. 18 mm was cut off the short end of the hex key, as illustrated in the image to the right. To do this, we used a Dremel tool with a cutting wheel and then ground/sanded any imperfections to make the surfaces flat.
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2. Next, we warmed the car to operating temperature. We like to take the car for a short (~15 min) drive to get the oil circulating and evenly heated.

3. With the engine warm, we lifted the car off the ground - enough for us to get under the middle of the car. We used a QuickJack along with a few jack stands to be on the safe side while under the car.

4. Before removing any oil, we opened/removed the filler plug near the top right side of the clutch bell housing with a 12 mm hex key. A 1/2" drive extension was needed to be able to reach the plug without hitting the engine.

5. Next we found the second filler plug on the oil sump, located at the lower centre rear part of the transmission. Then we opened/removed the filler plug with the modified 12 mm hex key from step one. This modified 12 mm hex key made it possible to clear the subframe. To get enough torque to loosen the filler plug, we attached a 12 mm socket and 1/2" drive extension to the end of the hex key.
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6. With a large oil pan immediately under the plugs to catch the fluid, we removed both drain plugs [3] using a 42 mm socket. We opted to empty the large oil pan between opening each plug to prevent the fluid from overflowing. We drained roughly 9L of fluid.

7. After most of the oil had drained, we removed the drain plug [1] located on the bottom of the clutch bell housing with a 10 mm hex key socket. Again, we had a large oil pan pan ready to catch the fluid.

8. With all of the oil drained, we then installed each of the drain plugs with new crush washers to form a tight seal. After hand tightening drain plugs, we used a 1/2" drive torque wrench to tighten each of the plugs accordingly. We were mindful not to over tighten the drain plugs to prevent stripping the threads. Since the owner's and workshop manual do not specify the amount to torque each plug, we made sure not to tighten the two 42 mm drain plugs [3] more than 45 lbs ∙ ft.

9. To be able to add the transmission oil, we attached a ~1m long hose to the end of a funnel, while putting the other end of the hose into the filler [2] on the oil sump (the plug removed in Step 5.).

10. New transmission oil was added until the oil was level with the bottom part of the filler [2] (or oil was just coming out of the hole). For us, this ended up being roughly 9L of oil. It was extremely helpful to put the bottles of new transmission oil in a warm place beforehand to help the oil flow faster when filling.

11. Filler [2] was closed and tightened using the modified 12 mm hex key created in Step 1.

12. The workshop manual states to add an additional 100g of oil through the filler plug located on the clutch bell cover [4]. For the oil we used, this was roughly 400mL of oil. Again, we used the funnel with the attached hose to make it easier to access the filler.

13. After all of the oil was added, we tightened the filler plug with a 12 mm hex key.

14. Finally, while still on the lift, we ran the car to get it up to operating temperature while periodically checking all of the filler and drain plugs for any leaks. We also tested that all of the gears shifted smoothly before moving. We continue to pay attention to how the gears shift, the handling feel of the rear end in corners and any of the plugs for leaks.

 

Sorry for the delayed response, I have been away.

Thanks for catching my mistakes/typos! I like things to be as near perfect as possible, so the input is much appreciated.

It seems I missed the window to edit my post - maybe a mod could help so I can fix the mistakes???

• Yes, you guys are correct, the drain plugs are 41 mm.
• Also need to include the seal washer for the small drain plug.
• Like rpissm, we ordered the copper crush washer from Ricambi for $2 - probably could find cheaper... Plus, the guys at Ricambi are great, so we don't mind supporting them.
• 25 lbs•ft wasn't enough pressure on the copper crush washer and leaked. We incremented the torque by 5 lbs•ft until the washer was tight and didn't leak. This probably varies a bit per car, so just our experience.
• We used the Mobil-1 differential fluid, the Royal Purple was our next choice if we weren't happy with it. Mobil-1 says it has some additive in it; however, we know others (although on other cars) who used it without any additional additives, but had chattering and poor cornering. From our understanding of the differential on the Testarossa, the worse case if we used too much additive, it would slip too much and act like an open differential. From that point of view, we wanted to error on the side of too much additive than too little.
• We can't see a problem with adding fluid only through the filler hole on the clutch bell housing. However, we defaulted to following the workshop manual since there may be a reason unknown to me... With a hose attached to a funnel, it wasn't too difficult to fill through the lower filler hole.