1980 Transmission Oil

[alternative]

Hey all, I wanted to do some maintenance on the car since I don't know the how old any fluids are, so I've been going around and doing this routinely. I can't for the life of me find out what type of oil I'm supposed to use or how much. I've been through all the manuals and the information is either misleading or is inaccurate. I saw another posting saying that GL-4 and 5 should not be used, GL-1 only. However the Fiat manual calls for SAE 90, which is a GL-4/5 oil to my research. Has anyone done a trans oil change recently that could help me out? Quantity and type is what I'm looking for to be specific.

[18Fiatsandcounting]

This is one of those questions where if you ask 5 different Fiat owners, you'll get 8 different answers.

The issue for the Fiat transmissions is that the synchros are brass, and GL-4 and GL-5 oils contain sulfur additives that are corrosive to the brass. Yes, some people use these oils and claim they work OK, but I'd personally be reluctant. GL-4 has less sulfur than GL-5, so you might be OK with GL-4 but again, I'm not recommending it.

Fiat specified GL-1 for the transmissions, which is simply not that readily available anymore. You can buy it online, and I've heard that Napa Auto Parts sells a mineral oil based transmission oil that is essentially GL-1 and what you need. Others have found tractor oil which is very similar, so if you live in an agricultural area, you might find it at a tractor supply place.

Other people use various oils by Redline, etc. Some might work just fine. SAE 90 weight oil would probably also work, but it's not ideal.

I'll have to check on the total capacity. Around a quart as I recall, but let me verify. I just buy two quarts and then add it until the transmission is full (oil at the lower lip of the fill plug on the side). By the way, I just pump it in with one of those cheap plastic hand pumps that screws into the neck of the oil jug/bottle, with a foot or so of clear tubing so I can watch it go in.

-Bryan
PS: I don't change the transmission oil like I do the engine oil. The transmission oil level gets checked and topped off as needed every few years, but I only drain and refill if I know there's an issue. Or the transmission is being rebuilt.

[Spider951]

I don't claim to be a transmission oil expert, but a recent experience I had with replacing my transmission (and therefore the need to fill 'er up with GL-1) led me to the following possible sources: NAPA GL-1; Warren Oil Co (their "Coastal" brand GL-1); Traveller brand GL-1; Chevron GL-1; Petroleum Service Co (their "Super S" brand) API GL-1. I ended up using the Traveller oil sold here locally by Tractor Supply Co; it was a bit confusing because it states on the gallon container that it is "Ford Tractor Transmission Fluid", but it seems to meet the requirements for basic mineral oil for our cars and states clearly that is SAE 90 GL-1. I'm sure there are other brands that will work. So far, my new transmission hasn't complained.

[Bagneaux]

I just ordered NAPA GL-1 on their website and picked it up at my local store. I have used this oil for three spiders and it worked great.