For those running the “Old School” T10’s etc. and having shifting issues that “increase” when the tranny warms up… and the hotter it gets, the worse it gets, I may have the answer. I have a 1965 Mustang with Ford/Warner designed T10 ultra-close ratio 4 speed. The car was my mom's since new (special order) and been in our family since then. I learned to drive in this car as well, and in 1986 I bought it from them, did a ground up rebuild and have about 10k miles on the car to date. The tranny was rebuilt by guys in downtown Los Angeles who were very well known and been around since the 50’s, replacing the bushings and synchro’s as the gears, etc. were in really good shape. When I reinstalled it, I filled it with Valvoline 90w gear oil…. The same tried and true tested gear oil my dad (engineer and racer) used for decades and myself as well. The tranny always worked very well! About 2 years ago, I needed to top of the tranny with about 1.5 ounces…. Was out of the 90w so made a trip to slep boys and bought a quart of Valvoline 75-90w gear oil, which stated on the label it was compatible with GL-4 spec oil (which is what our tranny’s call for). I also called Valvoline tech support and verified that the compatibility was a non-issue, which they affirmed. Over the next 2 years I slowly began noticing that at times it was becoming increasingly difficult to downshift into 2nd gear… no grinding, just acting overly firm. As the tranny warmed up higher, this occurred in 1st gear as well. Finally got to the point where, as soon as the tranny warmed up, it was difficult to downshift into 1st or 2nd gear without bringing the car to a complete stop. Ok, so since I am old school, and still trouble shoot by seeing, listening and feeling, I checked out the tranny……shift linkage was dead on, clutch seemed good but I added a little more reach (1/4”) for it, gear oil looked good, visually through fill hole- the internals looked good as well. Took her for a drive, and still the same. At this point I’m sitting back in my chair giving this some deep thought since it doesn’t make any sense…… and I come to the conclusion that this didn’t start until after I added oil…… checked around and found that over 100 people online are griping about the same thing, most are dropping their tranny’s and rebuilding them finding excessive parts wear (bushings, synchro’s). Although I am now thinking about pulling the tranny to see what’s going on inside, I just can’t convince myself that this is mechanical related….. it has to be chemical related especially since it appears to be temperature related. So out of mere “Gut Instinct”, I did a little R&D and found Brad-Penn makes a GL-4 specific gear oil…. Called and spoke to an engineer… he was great and after going through everything, he also agreed that although there was nothing else to indicate, he agreed, the chemistry issue was a real potential…. And he offered me a free oil analysis. I let “Betsy” sit for 1 month allowing all the oil and particulates to settle. I bought 4 quarts of BP GL-4 and dumped the oil…. The 1st 8 ounces I drained into a bottle for analysis…. This would also show the highest contamination but would give us the best idea of what was going on. I flushed the tranny with 1 quart of the GL4, then filled her up. The oil analysis came back that indicated early signs of bushing specific wear….. just what I thought was happening…. The Valvoline oil was reacting improperly and instead of transferring heat away, it was increasing the heat causing the bushings to swell and in essence being way too big forcing the synchro’s way out of alignment……. In short, what a way to destroy a tranny!!!! With the BP GL-4 oil in her, I took her out and immediately noticed a difference…even just the feel, vibrations, sound. I ran the freeway at 70+ mph, downshifting through the all the gears and can only describe it as “Silky-Smooth”. On my return trip I did the same thing, but when I exited the freeway and downshifted through the gears, I used no throttle- just merely pushing in the clutch and shifting the tranny….. same result….. absolutely “Silky Smooth”! Honestly the tranny has never ran quieter (although it was quiet before)……. and Valvoline gear oils will never touch any vehicle I ever own again! BTW, when I called the Vavoline tech support line and advised them on what had happened, the 20 something young lady, reading the PC said I must have bought the wrong oil. So much for consumer/product support. Anyway, I hope this helps those in need!
I looked at the Valvoline VV820 and VV831 when I had to fill my Muncie back up. I was gun shy with the GL4 and GL5 compatible on the label. I opted for Richmond GL4 from a local speed shop, I'm happy with the way it shifts.
Well that’s one of the best testimonies for oils I’ve heard. I was going to suggest the pilot bearing/bushing was getting dry and binding. I did use valvoline motor oil a long time ago and it foamed so bad I took it out. Never used valvoline anything again.
Tha is what I was considering as well, but because it shifted so fine when cold I just couldn't buy off on that fully....and why I just didn't get in a rush to pull the tranny. Glad I let patience over-ride my typical do it attitude! HA!
What is a Ford/Warner designed T10 ultra-close ratio 4 speed. How close are the ratios? I can't beleive that 1.5oz of anything in how many ozs total could hurt.
The T10's came in 2 general styles...Top Loader & Side Loader.... I have the Top Loader, now Borg Warner actually designed these for Ford but Ford Built them, that is why they are referred to as the Warner Designed Ford T10. I was very lucky and about 15 years ago i got to meet one the T10 engineers... I still have the original purchase papers, showed them to him and he knew exactly what I had. He advised me that over the years of production, there were 235 combinations of those tranny's that could be ordered. IIRR, and I talking off my memory, the gear ratios are.... 2.64 first, 1.61 second, 1.23 third, and 1.00 fourth. I can tell you that with my specific diff gears, 1st is a little slow off the line but 2nd is absolutely brutal in acceleration. It is really best in a road course/racing type environment. IIRR, the standard T10 1st gear was a 2.88.
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