HOTROD | How-To - Transmission

Mopar Quick Tech - Fluid For Your Four

A quick bit of tech so your car won't wreck.

We enjoy all Mopar muscle cars, but particularly enjoy driving vehicles equipped with manual transmissions. There's just something about the synchronized performance of the arms, legs, mind, and automobile that results in the perfect power shift, which simply cannot be duplicated by an automatic transmission. So if you're lucky enough to get to row through the gears of your Mopar, you certainly don't want to miss that feeling because your car has transmission problems. And although the A-833-especially the early big-bearing and 18-spline Hemi units-are pretty tough, choosing the proper fluid can have a definite impact on the life of your transmission.

We've recently had a couple of letters and several questions on our web forums regarding running automatic transmission fluid (ATF) in the A-833 manual transmission, so we decided to give you the facts about this subject and let you decide what lubricant is correct for your application. From the factory, the majority of early Dodge, Plymouth, and Chrysler products equipped with the A-833 transmission had hypoid gear oil installed. And though we've heard a rumor that some late-'70s trucks had ATF installed from the factory, we have a feeling this is based on a technical service bulletin issued by Chrysler instructing that dealer mechanics try ATF if a truck owner was experiencing hard shifts.

While automatic transmission fluid does act as a lubricant, you must remember that it is a hydraulic fluid as well and lacks the additives required by the shearing (hypoid) action of helically cut gears like those in the A-833. ATF is also thinner than gear oil, and we've seen it find leaks anywhere a seal or tolerance is marginal. We called Jamie Passon over at Passon Performance who verified that ATF lacks the cushioning effect of hypoid gear oil and would cause premature wear of the synchronizers.

We agree with Passon's recommendation that good 80W90 weight gear oil is the lubricant of choice for most A-833 applications, and we've also had good luck with synthetic lubricants like AMSOIL Severe Gear. Engine lubricants and ATF may seem to offer an advantage, but you'll end up damaging the internals of the transmission, which can get expensive quick. So while it can be tempting to use the next trick someone tells you about, like using ATF in your four-speed, it's definitely not worth the risk of potential damage.

2a Many popular Mopars were equipped with the A-833 four-speed, and we’ve heard of several tricks to make them shift better like running ATF or even motor oil in the transmission...