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Transmission additive

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This may be a dumb question, so forgive me if it is. Transmissions are probably my weakest area of knowledge. So I have a 4 speed with what I believe is a sticky or bad syncro gear on third. Its temperamental going into 3rd either from 2nd, or downshift from 4th. A guy I know who has owned older mustangs before told me I can add a Lucas additive to tranny to try to free it up. I realize the best fix is pull it and fix it right. Its summer and we only get 3 months or so and I hate to lose convertible weather. I'd love to try some Lucas. I dont think I have much to lose, if it doesnt help, then I pull it this fall. 

   So how can I add some? I'd have to drain a equal amount, say 1 quart, then add 1 quart of additive?  I assume there would be drain plug on very bottom and then a side fill via some small plug? I dont own a lift (another topic) so its frustrating.


Thanks in advance!

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I think the Lucas transmission additive comes in smaller bottles, maybe 8 ounces, or so. I like Lucas products, I use their fuel system conditioner all the time.


That said, I would guess that you have a bad synchro, but the additive might help short term.



“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein


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First, make sure your clutch free play and the shifter linkage are in good condition and adjusted properly.


Second, drain all the gear lube out and refill with a high quality GL-4 spec conventional gear oil. More toploader shift problems are caused by incorrect gear oil than anything else. You're not likely to find it at Walmart, but a good parts store. It has to be GL-4 spec, not a GL-5. The 5 will cause shift problems and absolutely no synthetic in a worn tranny.


I've used the Sta-lube GL-4 with good success. Amazon carries it, as does NAPA if you have one local.




Some toploaders have a drain plug in the bottom of the main case, but not all. If yours doesn't, pull the bottom very bolt in the tailhousing.  Fill plug is on passenger side of the main case. It's a square drive plug, so you need to use an open ended wrench. Fill the case until it dribbles out the hole, about 2 quarts.







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Shifter wear and adjustment can cause some shifting difficulty as well. I would go through the adjustment procedure before doing anything drastic like pulling the transmission



"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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