GM Synchromesh Friction Modified

[72MetallicMalaga]

I see that redline MTL is the go to tranny fluid for many FAQers, but has anyone tried GM Synchromesh FM in the Getrag 245? I don't see any threads on it.

 

I used to use it in a lot of my cars, and wanted to see if anyone has first hand experience before I try it this weekend...

 

 

[TobyB]

Nope.  But if it's used on the B-W cone style synchros, it'll work fine.

With the MTL, if it feels a bit light, you can mix it with MT90 to give more

synchronizer action...

 

The 245's not too picky-  after Getrag gave up on the PorSha style, things became 

downright predictable.

 

That said, I can't think of many manual transmissions actually built by GM after the Muncies.

And while the Muncies have positive attributes, I don't recall the shifting being one of them...

 

t

[rstclark]

While I’m not clear on the product you are asking about. GM Synchromesh FM

I have used ACDelco Synchromesh Transmission Fluid  with great success 

It works like a transmission rebuild Some people blend it with standard 90w gear oil but I use it full strength

Maybe someone can comment about this for use for Porsche syncros and BW syncros

 

[TobyB]

I did, above.  

I will do so, one more time:

 

GM uses B-W style syncro cones, so their products ought to work,

generically, with the B-W style Getrags.

Specifically, the tolerances may vary,  and so may your mileage.

 

t

[rstclark]

Thanks Toby   Good info

I don't think I will use it with a 235 dog leg  CL  since I think it has the older Porsche synchros   Yes ???

What is the preferred long term lubricant for a 235-5 ?

[rstclark]

Oh  Who really cares about mileage ??   LOL  

[72MetallicMalaga]

Alright small update, replaced Getrag 245 tranny fluid with the GM Syncromesh Friction Modified, and it's great so far, i've put about 100 miles on the vehicle already.

 

Ill try Redline MTL next.

 

@rstclark, the stuff you have pictured is the non "Friction Modified" version, but glad to hear you like that as well. Prob a little less expensive too, the FM version is $24 a quart.

 

Edited November 17, 2022 by 72MetallicMalaga

[conkitchen]

This is rather apropos, I just got off the phone with Jim at Metric Mechanic about my limited slip diff he built for me.  Prior to today's call I was speaking with him about using ATF in the 245 CR dogleg he also built for me.  

 

1) The trans has the Borg Warner syncros and tapered bearings. He was 100% on using just straight ATF. He even went and said to use the cheap stuff.  Have to say the trans does shift better than any 245 I have driven.  Albeit it's rebuilt.  

 

2) The diff. After installing and filling with gear lube, it would make a groaning noise as it rolled.  I called and he asked did we give you any limited slip additive? I said no, he said go buy the AC Delco Limited Slip additive. I did and it made a difference. What's funny is while asking him about using ATF in the trans I asked what type of lube for the diff. His reply was it really won't matter what you put in there.  

 

Moral here kids. Use ATF in your 245 and GM LSD additive in your diff.  

Edited November 17, 2022 by conkitchen

[jimk]

Be careful of the "cheap ATF".  It may have poor "4-ball wear" (ASTM D4172) characteristics. Test scars ~> 0.40 mm are bummers.  The input shaft gear to layshaft takes load in all gears except "direct" and when it's worn out, you're done.

Edited November 18, 2022 by jimk

[M3M3]

separate LSD additive is NOT needed in an LSD if the oil you use already has friction modifier in it.  like redline 75w90.  the more friction modifier you use in an LSD, the less "limited" the slip is.  more is NOT better.  just use the right oil up front and do not add additives. 

 

race oils like redline Shockproof have less friction modifier than their regular gear oils for more clutch lockup.  redline oils with "NS" in the name have no modifier.

 

new LSD's need to be broken in.  after installation the car should be driven figure 8's to get the clutch disks burnished in and the oil with modifier spread around.  "groaning" of a new diff is normal before break in.

 

moral here...do not just dump LSD additive in your diff.

Edited November 18, 2022 by M3M3M3