M5R2 Fluid upgrade (for brass synchros)

JT15601

Registered User
Ok so I'm going on my 4th, yes 4th, transmission rebuild on my 1989 sc (full bolt ons and some extras) and I am going to all brass synchros since my 3rd is going bad (fiber blocker ring). I personally like the feel of the brass synchros on 1st 2nd and 5th gear. So I'm replacing the 2 fiber ones with brass again. I blew the original brass ones (after 1st rebuild) on 3rd and 4th out racing because of a bearing failure. Had to replace with my old fiber ones. At any rate. I'm going full brass synchros.I read a lot of back and forth talk about what fluid to use. I run atf 4+ from Carquest with about 4oz of Lucas oil additive. (Just my personal mixture. What's the optimum combo of fluid for all brass synchros?
 
A good quality synthetic ATF, forget the Lucas stuff. One bottle of stinks like hell Ford friction modifier.

As far as I know this has been the recipe for M5R2's. Correct me anyone if I am wrong your input is welcome.
 
What type of ford friction modifier? The same stuff that goes in the differential? Because that's all they said they have
 
Yes it's the same stuff, just beware the smell is something GAWD awful. It can be used in the diff as well when you change the oil for the posi-track clutch packs.
 
Note that the specialized FM used in manual transmissions is NOT the same FM used in Limited Slip Differentials. It is important to understand that there are different FM compounds for different automotive applications. Some modify to add slippery-ness/reduce grab and some modify to add grab, based on the materials in the unit. If you go back to brass, use the same fluid that the trans came with from the factory.
 
I know the friction modifier from ford is to add grab to the clutches in the rear diff. I just swapped over to a 3.27 center section I rebuilt and went through all that. So the idea I'm getting is shoot for just plain synthetic atf. No additives? And just a thought, since the FM helps the clutches grab I'm the diff wouldnt that carry over the the brass blockers grabbing too? I'm trying to set this car up for 1st to 2nd and 2nd to 3rd power shifts because it takes those a lot. I need it to go into gear under stress quickly every time. I'm in no way worried about casual driving feel. And I don't really believe in short throws because they reduce leverage. My stock shifter is shimmed perfectly instead
 
A great way to crack a brass syncro is for it to grab too quickly.

A syncro has two jobs. One is to engage the outer cut teeth with the teeth on the driven gear and brass needs all the help it can get to do that smoothly, etc. - the other is to use the inner cone surface to spin up the target gear...what makes you think it needs more help in both/either of those tasks than originally designed?

If you want different performance in that example, use a different material instead of brass, then use the appropriate fluid/additive(s). Sorry if I missed it, but have you tried CF syncros yet? If you're back to brass because of money, then use them as intended, sans 'grippy' additives, and don't hurry shifts, etc.
 
My bad I never had brass synchros and as far as I knew from Fast Ed who works at Ford they carried only one type of friction modifier. I put well over 60-70K kms on that tranny and pounded it at the track, when I dumped it because of a rotten body the tranny was still perfect.
 
I haven't tried cf synchros yet. I'm trying to budget out the bird because I also have a lot of other projects as well. And I've never had a brass synchro crack and I've beat them up pretty good. Only the stock fiber ones I have problems with
 
no brass syncro probs here, with NO FM, 500+ rwhp and driven hard. I crack gears before blocker rings.....
 
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I just rebuilt my m5r2 and decided to try mercon ATF like it called for. No friction modifier. Replaced some blockers with brass ones and reused some of the originals that looked ok. Shifts better than it ever has before. I have used gm synchromesh oil in the past. From now on, I think I will continue to use ATF. My recent rebuild is the happiest I've ever been with how my trans performs. Other than the napa output seal that leaks slightly, nothing ever seems to go perfect. Should have grabbed a ford one instead I guess.

Chris
 
I have no idea what synchros are in mine, but I use Mobil1 ATF and it was a big improvement over whatever was in there previously (Syncromesh, maybe).
 
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