How to Change Manual Transmission Fluid
This tutorial will walk you through the process of changing manual transmission fluid on your Fiat 124 Spider. According to FIAT, this is a long life fluid with no service interval listed, but I didn't like that my transmission would occasionally get notchy. After missing 3rd gear twice due to that inconsistency (especially when hot), I decided to try something different, and I was dying to try out our 75W-90 GL-4 MTF in this car. My car had 1,450 miles when I drained the transmission fluid for this tutorial.
- 24mm or 15/16" wrench (I was unable to fit a 24mm socket between the transmission and the subframe to remove the fill plug)
- Shop towels
- 12mm socket and ratchet
- Oil pan
- Optional: ft-lb Torque Wrench.
- 3 Quarts of Synthetic 75W-90 GL-4 or your favorite manual transmission fluid.
- A fluid pump
I've personally used AMSOIL 75W-90 GL-4 MTF and AMSOIL Synchromesh and had great experiences with both in the past. In the 124 Spider, I'm using the 75W-90 GL-4 MTF. At the time of this edit, I've been using the fluid for two years and am pleased with its performance.
The 75W-90 GL-4 can be a bit stiff on cold mornings below ~40F in freezing temperatures for the first mile or two, but works well in hot conditions and with severe driving. The Synchromesh fluids can be a bit more notchy when very hot but will shift better on colder mornings than the 75W-90 will, at least until the transmission warms up a bit, and will be better suited for normal driving conditions. However, Synchromesh fluids mighit have lower EP additive concentrations and as a result, may not be well suited for exceptionally severe driving, frequent racing, and modified cars where hard launching and shock loading are the norm. I personally use the 75W-90 since I only drive the vehicle in warmer weather and it stays in the garage over winter.
Some people have also reported good experiences with the Ford XT-MS-Q5 fluid, which seems to work well but is a tad more expensive. Other synchromesh fluids may work as well. Choose the fluid that's best suited for your driving conditions. Note that this same transmission in the NC Miata used a 75W-90 GL-4 MTF, so that's what I'd recommend sticking to.
- For ease of filling, I used the AMSOIL Bottle Hand Pump, which screws onto the quart and gallon bottles. This made filling the transmission a breeze.
- FCA does not list a service interval for this fluid, but I don't like keeping break-in fluid in gear boxes for very long. A picture further down explains why.
- There are crush washers on both the drain and fill plug. You may change these if you want to, but I did not feel it necessary to do so. If you want to change them, pick some up at your dealer prior to starting this service. I typically change them every other service interval if they look damaged.
1. Lift the car securely. If you can only lift one side of the car, lift the front, as the drain plug is toward the rear of the transmission.
2. Once underneath the car, use a 12mm socket to remove the 4 bolts holding the cross brace on.
3. The fill plug and the drain plug are shown here, facing the driver's side of the car. Make sure you can remove the fill plug before you remove the drain plug.
4. Using a 24mm or 15/16" wrench, first remove the fill plug, then the drain plug.
5. For the first transmission fluid change, you'll find a substantial amount of metal shavings stuck to the magnet on the drain plug. This is normal, do not be alarmed. This is all break-in metal. Simply wipe it off on a towel.
6. The oil will most likely have metallic swirls. Note that this is also break-in metal, do not be alarmed unless you find chunks of metal (I found none).
Obligatory AMSOIL promo shot
7. Reinstall the drain plug and torque to ~29-42 ft-lb.
8. Fill the transmission to 2.2 quarts (2 quarts + 6.4oz). If using the AMSOIL bottles and fluid pump, the AMSOIL bottles are marked on the side with a bar visible to show remaining fluid. Fill the full two quarts until empty, then pump the 3rd bottle until the level shows 20 ounces still remaining in the bottle. I know what you're thinking here...if the trans holds 2 quarts and 6.4oz, why is he filling 2 quarts and 12oz? The reason is simple: there are a few ounces of oil still left in the pump and the hose. Alternately, you can just keep filling until fluid starts to trickle out of the fill hole, which should bring you to about the same point.
9. All in all, you should have filled 2 full quarts and ~6.5oz. If you pour the remaining oil from the two empty bottles, and empty the pump into the 3rd bottle, you should have ~25.5 ounces (or just over the 24oz mark), validating that the transmission was filled to the correct capacity.
10. Reinstall the fill plug and torque to ~19-28 ft-lb.
11. Reinstall the cross brace and torque bolts to ~22 ft-lb.
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