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Tremec Magnum XL Fluid Discussion

67GTA

TMO Race
264
248
SoCal
I just read an article that says Tremec recommends ONLY Dextron3 ATF in the Magnum.
I had Amzoil in my wide ratio magnum and it shifted fine, my new Close ratio Magnum will have ATF so we'll see how that goes.
https://www.streetmusclemag.com/news/are-you-using-the-correct-fluid-in-your-tremec-transmission/
agnum (and I didn't realize my shot of the bent pan above had the magnum), I had the following experiences with fluid:

Mobil1 ATF - D3 fluid - Way too thin when its hot, @BillyJRacing (Billy Johnson) recommended it as it was what was ran in the IMSA cars
With a cooler its better, but still warmer races I felt that it wore down the synchronizer rings more quickly than other options

Currently in the magnum is the BG (from OPM of course):
BG Products Multi-Gear Concentrate - MGC
BG Products Syncro Shift II Synthetic Gear Oil 75W80 API GL4 (which isn't a D3 fluid) - " BG Syncro Shift® II may be effectively used in all domestic and foreign vehicles where engine oil, ATF or GL-4 gear oil is specified as “service fill” for manual transmissions. Also suitable for use where GM PN 12345349 (specification 9985648) FORD PN D80Z19C547A, PN ESRY19C547A and MERCEDES-BENZ PN 900260315 are specified. "

This fluid works much better for me, slight increase in shift effort when its cold, but usually by the end of the warmup lap that's over and done with. Much better protection and shifting characteristics it seems even when hot, especially when the idiot driver forgets to turn on the transmission cooler (plumbing an automated circuit for that soon). My magnumXL is setup with a number of brass and carbon parts, not many organic lining parts in it so that may impact fluid selections for some. (I believe most magnums are that way but a TR6060 might be pickier about fluids)
Decided to start a new thread dedicated to this discussion on fluids for the Tremec to keep the oil pan thread from drifting.

Quick backstory: Converted to the Magnum XL in December 2019 after the MT-82 gave up. The conversion kit I used from Modern Driveline included the Tremec HP-MTF, which is now their spec fluid for the Magnums. Ran the HP-MTF for 8 track days from January-May, in which time the transmission performed really well. A bit notchy when cold, but seemed to be very much in line with everything I had read about the Magnums and never had any gear clash whatsoever.

Decided to change the transmission fluid early June, at which time the HP-MTF wasn't in stock anywhere. I run Royal Purple throughout the car, so decided to make the switch and give the Synchromax a try. I've since read that Tremec's can be finicky with fluids, but would never imagine how drastic the issue can be. On that first track day, it started to have gear clash on 4-3 downshifts. What's strange is it's only when cold, then by the end of warm up lap it downshifts fine. Still not believing that a fluid change could cause this, I bled the clutch, verified the clutch was disengaging properly, etc., which all checked out OK. Ran one more day at Buttonwillow, and exact same thing - gear clash when cold - good to go once warmed up.

Switched to Mobil 1 ATF, ran a few heat cycles (same gear clash), drained and refilled again with Mobil 1 ATF. Still the same. Tremec finally had the HP-MTF back in stock, but it wouldn't arrive before the next track day. Switched to TORCO MTF, based on the viscosities being the closest I could find to the Tremec HP-MTF. Marginally better, but still clashes when cold. Now that I have the HP-MTF here, I plan to change back before Auto Club 2-day on Oct 3&4. As you can imagine, my confidence isn't very high that this will magically remedy the problem. I'm concerned that the fluid change actually damaged the 3rd gear synchro, and I fear that I'll have a fight on my hands trying to pursue a warranty claim with Tremec since the RP Synchromax is not one of their "approved" fluids. Again, hard for me to imagine that a fluid can (or should) have this much impact. Bowler Transmissions spec'd the Royal Purple Synchromax for their Magnum kits. Maybe if you start with that and stay with it, everything is fine? Beyond frustrating having this type of issue when the whole rationale of dropping $6K on the conversion was to eliminate the worries about the transmission.....

The chart below is the cold and hot viscosities of several different ATF's and MTF's for reference

1600400973224.png

IMG_5139.PNG
 

JAJ

TMO Addict
791
734
In the V6L
This is a friction-modifier problem, not a viscosity or spec problem. The TR3160 in my GT350 was very notchy and clashed a lot, so I ran a test with every fluid I could think of. Result is that I'm running Motorcraft DCT fluid (the MT82 fill) with XL-18 friction modifier. Shifting is excellent and it runs way cooler on the track
 

67GTA

TMO Race
264
248
SoCal
The TR3160 in my GT350 was very notchy and clashed a lot
Was this primarily during start-up temps, or consistent through the range of operating temps? Clash on up shifts, downshifts or both?

Appreciate the insight on the Motorcraft MT-82 blend - haven’t seen anyone else recommend that, but I agree completely it has to be a friction modifier issue, especially since the viscosities vary so greatly across the “approved” fluids.
 

JAJ

TMO Addict
791
734
In the V6L
Was this primarily during start-up temps, or consistent through the range of operating temps? Clash on up shifts, downshifts or both?

Appreciate the insight on the Motorcraft MT-82 blend - haven’t seen anyone else recommend that, but I agree completely it has to be a friction modifier issue, especially since the viscosities vary so greatly across the “approved” fluids.
It was worse when it was cold - 1 to 2 the first time on a trip always ground - but it never really went away either. Every once in a while I'd get a reminder. I've been driving standard gearboxes for decades and this one was good on any shift that didn't involve second or sixth. With the MC DCT+XL18 fill, it's stiff when it's cold, but it never grinds. BTW, I tried DCT without XL-18 and it wasn't as good. It needs the FM.

On the temperature thing, I did two track days last week. Engine oil was 250F, diff was 220F and the gearbox was 175F.
 

Fabman

Epic Contributor
2,975
1,957
Pleasanton: 1/2 way between Sonoma and Laguna Seca
W2W Racing
20+ Years
This is what I ran in mine and shifting was really good.
I would prefer that reverse was located in a different spot but other than that its a premo transmission.

 

Equinsu

TMO Intermediate
17
20
Bay Area CA
Bought my T56 from MDL as well and back then they supplied the Amsoil ATF fluid which gave me no problems. By the time a change was due I saw Tremec came out with their own fluid and figured why not since they make the transmission. So far I’ve noticed no difference between the two meaning I haven’t had any issues with either. Anytime I do any type of oil change I order my next change to have on hand as who knows when stock will get low.
 

67GTA

TMO Race
264
248
SoCal
Wasn’t able to make the Oct 3&4 track days, so no definitive update if the Tremec HP-MTF remedied the 3rd gear clash or not. Couple short test drives and it was still doing it, but not really heat cycled yet. Confidence is still very low on this being the “fix”. According to one of the tech guys I spoke with, the synchro rings will glaze with certain fluids, and it’s hit or miss if they come out of it with another fluid change.

While researching all of this, I’ve learned some interesting facts about the Magnum XL’s, and differences that exist between the 2.97 and 2.66 boxes. Both use an advanced tooth gear and synchro design on 2nd gear, paired with upgraded carbon fiber blocker rings. This is an “upgrade” from the earlier design Magnum’s which used only symmetrical gears and bronze rings. The “upgrade” was intended to improve cold weather 2nd gear shifts, however the advanced tooth is not the best performance option.

Where the two boxes differ is 3rd gear. The 2.66 box uses an advanced tooth design on 3rd, while the 2.97 uses a symmetrical type gear and synchro. Again, the advanced tooth design is a carry-over from the OE TR-6060, where the priority was placed on smooth shifting in all climates, rather than best design for optimum performance. The owner of Modern Driveline, Bruce, mentioned this on a call when I was describing the issues I’m having. He said that the Tremec Elite distributors have been trying to convince Tremec to use only symmetrical gears in the Magnum and Magnum XL’s, as most of the aftermarket sales are for performance oriented vehicles.

Magnum XL (2.97 first):
1- Symmetrical, Bronze
2- Advanced, CF
3- Symmetrical, Bronze
4- Symmetrical, Bronze

Magnum XL (2.66 first):
1- Symmetrical, Bronze
2- Advanced, CF
3- Advanced, Bronze
4- Symmetrical, Bronze

As mentioned above, my confidence is very low on the Tremec fluid eliminating the gear clash, and after learning about the advanced tooth gears, I’ve decided that an upgrade is in my near future. I have to say that I’m not thrilled about pulling the trans again and disassembling a gear box with 2,000 miles on it, but I’m done with the gear clash. I plan to convert 2nd & 3rd gears to symmetrical, upgrade the 1-4 blocker rings to full carbon fiber, 5-6 to hybrid and replace the 1-6 shift pads with bronze. What the hell, another $1,000 in parts & $500 in specialty tools on top of the $6,000 already spent to get here. In hind sight, maybe I should have ordered an upgraded Magnum XL from Liberty Gears from the start - would be money ahead and one less time pulling the trans. I guess there’s some comfort in having the right tools and the know-how to tackle any future issues without having to wait on the long turnaround times from a Tremec dealer. Still just baffles me that all of this came from using the “wrong” fluid.
 

67GTA

TMO Race
264
248
SoCal
^^^ so what you're telling me is that with lower amounts of power in a car that will see year-round street driving, there's no reason not to want the advanced tooth design in 2nd and 3rd.


Norm
From what I understand, it has less to do with power and more to do with higher RPM applications. I would guess you’re shifting your 3v well under 7k, so should be fine. The advanced tooth was OE in a lot of very capable cars (although most are far lower redlines than the Coyote’s).

Just be VERY selective with your fluid and stick to Tremec’s recommendations. I swear by Royal Purple, however based on this whole experience, steer clear of their Synchromax for the Magnum.
 

Norm Peterson

Corner Barstool Sitter
I'm shifting well under 7000, that's for sure. There really isn't any point in taking it much past 6000 with only the FRPP cold air & tune for roughly the same 315 HP claimed for the 2008 Bullitt and 2010 GT. With it being a street car in NJ, there isn't a whole lot more I can do that won't risk running afoul of emissions inspection.


I don't need anywhere near Magnum XL strength, but I really do want to get away from the 3650 with its rather wide 2-3 and 4-5 gear spacings. The only other potential option I've found so far is the close ratio TKO (2.87/1.89/1.28/1.00/0.82), which while the 2nd - 3rd doesn't change much would at least give me a decent 5th and slightly better 1st and 2nd gears than the close-ratio XL for around town. That would come at the expense of losing the more relaxed 0.68 top gear in the 3650 or the 0.63 in the XL. The 2.97-low XL is not an option.

Years ago I was running a Tremec 3550 in a different car that worked flawlessly with GM Synchromesh.


Norm
 
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