so im gonna do a L43 4sp to L52 5sp swap on my 80 yota.has anyone ever flushed out,just to clean out,a manual trans and transfer case before putting all new fluids in? what would you use? trying to do as much preventative maint as possible BEFORE the swap,marlin shifter socket and ball,clutch,all rubber boots and powerwash the whole thing.PO said it has 5k on rebuild,everything feels really good as far as play.all suggestions welcome!!

 

Hopefully someone else will speak up, but I took something like brake cleaner, sprayed as much as I could inside the case, let it dry completely, then filled it up with gear oil. I don't remember if it was brake cleaner or something else like it...but I feel like it was brake cleaner.

 

I would not clean it with anything. Drain the transmission and fill it with Mobil 1 gear oil and add an additive such as B&G brand or other reputable brand of additive. I have had my truck since new (156,000 miles), I use Mobil 1 gear oil and B&G additive, I have no gear noise, problems shifting including reverse, sloppiness or bearing problems including the main input bearing (which was famous for failure until 1983). I change my gear oil every 5 years.