Lucas Transmission Additive...any good?

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Apr 11, 2009
My wife's 73 Buick has a Turbo 350 automatic transmission. The tranny has about 120,000 miles on it. It recently began slipping a little in second gear...when downshifting going up a hill, it occasionally has problems shifting into second gear. One of the guys at Advance Auto Parts told me that his truck tranny would not shift into high gear. He added a bottle of Lucas Transmission additive and after driving it for a short time, it resumed normal operation. So I bought some but haven't used it yet. I'd be interested in hearing from people who have had practical experience with this product.
I put it in a 1970 F100 that I used to own. Didn't do anything, but the trans was old. I've had better luck with Auto RX in the transmission.
What is the condition of the current fluid and what kind is in there? what type of service history does this unit have? Is it a rebuilt unit or the original? I have heard some very good results from folks who have used the Lucas trans additive, although I would tend to use it as a last resort to taking in for repair. Instead, you might consider Auto-RX for your issue. Check the website and look for trans application.

I think I remember that unit has a vacuum modulator. Make sure it is working correctly since it has an effect on system pressure, which affects shift quality. I cannot remember if that unit also has a throttle cable, (I think not) but if it does, that would affect kickdown and pressure increase for higher throttle operation.
Make sure that the ATF level is correct.

Bumps of the viscosity which leads to higher pressure. Very tacky/sticky and might help seal internal flow leaks increasing flow.

I would flush it out with a high mileage ATF.
The reason these kinds of things get sold is that everyone wants a quick fix, dump the bottle in and go back to drinking your Coors and watching the boob tube. When these things do work, it's mainly because the fluid was simply low, and the snake oil brought it back close to full.

What you really need to do is check the fluid/change the fluid to new ATF. Do a couple drain and refills with some OTC fluid, then stick in some good synthetic.

When someone at an auto parts store tells you how to fix something, do the opposite.
I don't think I would put it in a trans unless you were out of options and didn't have the means to rebuilt it.

Give it a try and see what happens!

I used a bottle of the stuff in my 850s power steering at around 100K miles. The spool valve was full of garbage and I had some nasty hard spots (eventually, no assist at all) and it cleared it up. Thing STILL works great.
I have used it in my U140F Lexus trans-axle,it seemed to work well.But I would not recommend a whole bottle.Try replacing your vacuum module on the r/h side of the trans,and drop the pan,investigate what it looks like in their,and change the filter.
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