tbear853

In another thread (dealing specifically with my install of a Hurst Billet shifter and modifications to that shifter and the addition of a "clutch pedal extension") I have made reference in several posts about how "old school" muscle car transmissions shifted smoother and with less effort.

January 1st the wife and I took the Mustang for a drive to Roanoke and then back home via Blue Ridge Parkway (dinner at Peaks of Otter) ... and I was enjoying the whole deal and was thinking about a bunch of threads I was reading the other night about shifting, knashing, grinding, nibbling, recommended lubes, etc .... and it occurred to me that really, our Mustang doesn't do any of that except when the trans is cold and a fairly quick (brisk like) 1-2 or 2-3 shift is attempted .... so we don't do that.

I did change the lube from factory fill to Mobil 1 ATF Synthetic back in the late Summer (car had maybe 23K) ...
... but I may try some Texaco Havoline Dex III/Merc conventional come Spring time. I've read where some at Tremec suggest that the lesser slipperiness is thought to aid the synchro rings.

Once warmed up even just a little, it really shifts OK, but as I have said before, not like those old muscle car 4 speeds. I got to thinking about the "why". I had long ago with my '74 Toyota Celica GT and later my wife's '76 Celica GT attributed it in part to the internal shift mechanisms ...
... and I am sure that is a part of it as the '84 Mustang 4 spd and '86 Mustang 5 spd GTs the state had for us to use back in the day were also some notchy.

I have this habit, almost a double clutching but very abbreviated, not all the way out with the clutch but just enough that as I pass through neutral I pause as I ease up and press it back as then the engine RPM has dropped because I let off and engine thus slows the clutch disc and input shaft, trans slips into gear. It is a habit I've had for over 40 years. I tried it after an older cousin had explained it to me and I found it greatly eased shifting in my school bus and mail truck driving jobs. I guess it's become so second nature that's why I still do it when just driving, even in my wife's Forester 5 spd. and it's not as notchy as this Mustang if you are just pressing the clutch and pulling the stick and letting out on the clutch (but it too is stiffer when cold). Other times when not in a hurry, I'll just let up off the throttle and ease the trans into neutral and then push in the clutch and go from neutral to the desired gear, all in one movement however.

That's not to say I didn't throw what we called "power shifts" when running them cars back in the day, that was fun too ... then. WOT, start preloading just before the shift, just fan the clutch in/out and the trans was in the next gear, no scrapes, no mechanical drama except tire slip (or so one hoped). But that was when I was a young toad and didn't mind yanking a trans to do a clutch change or replace a brass ring or maybe a U-joints on a Saturday afternoon. But those old muscle cars big 4 speeds were so buttery smooth even in everyday driving, just push in clutch and move stick (Hurst Comp+ in all mine) and you were in next gear, no notchiness that I ever felt. There was no need to pause in neutral, but when just cruising I still sometimes did after acquiring the habit I'm sure.

And those old transmissions had a shifter bolted on, three rods running up to the side cover and levers, and alignment was in neutral with a 1/4" L shaped pin (still have mine), and inside the side cover were forks that road on sliders ..... easy to work on they were! But as heavy (that Dart's NP A-833 4 speed was a monster, way heavier ... and stronger .... than a Muncie, and is still the heaviest 4 speed put in a pass car) as they were, as strong as they were, they shifted so sweetly. I never owned a Ford with a T&C top loader, but a buddy who had a couple 70 Torinos with 429 SCJs did and they likewise, shifted just great. The only car I drove back then that I recall shifting badly was a Chevelle with a OEM Muncie shifter .... but that was a crap shifter on a good day.

So .... to continue, I came home and did some math. Mustang's TR3650 ratios 3.38 / 2.00 / 1.32 / 1.00 / 0.62 so if you take it to say 6000 in each gear:
1-2 drops rpm to 3550,
2-3 drops rpm to 3960,
3-4 drops rpm to 4545,
4-5 drops rpm to 3720.

New Process A-833 4spd as in my '69 Dart Swinger 340 ratios: 2.66 / 1.91 / 1.39 / 1.00 so if you took that one to 6000 in each gear:
1-2 drops rpm to 4308,
2-3 drops rpm to 4366,
3-4 drops rpm to 4316.

M-21 or M-22 Muncies as in my GTO or Chevelle both had ratios 2.20 / 1.64 / 1.28 / 1.00 so if you took those to the same 6000 in each gear:
1-2 drops rpm to 4472,
2-3 drops rpm to 4682,
3-4 drops rpm to 4687.

Even the wider ratio M-20 with it's 2.52 / 1.88 / 1.46 / 1.00 ratios:
1-2 drops rpm to 4476,
2-3 drops rpm to 4659,
3-4 drops rpm to 4109.

So I see where this Mustang's TR3650 wider spaced ratios (I knew it was a wider ratio spread, just never done the math) would make life harder on the synchro's life as they are forced to slow that spinning "input gear train" (includes: input shaft / gear / countershaft gear set / any intermediate gears on MS / clutch disc / and any lube windage effects) at a much faster rate to drop those extra RPMs on an upshift .... especially on that 1-2 and 2-3 upshift .... and why it seems so that it likes my "abbreviated double clutch" upshifts.

Likewise, on downshifts, the synchros are asked to speed up the "input gear train" speed to match the higher flywheel speed that desired lower gear will call for, hence "heel and toing" (in a hurry) or simple double clutch with a throttle tap between gear selections (when not so much in a hurry or not braking at same time).

Getting back to upshifts, take my '69 Dart above at 6000 for example (I usually shifted it around 5500 if in "anger" in real life), those synchro had to scrub 1692 rpm off the "input gear train" speed on that fast 1-2 shift ...
... while this Mustang's synchro has to scrub some 2450 rpms off the "input gear train" speed in the same time frame if that same 1-2 WOT powershift is attempted.

That's a bit more work .... a "lot more" if one were to compute the change in the inertia involved with the whole "input gear train". It also occurred to me that besides all that, the 5 speed has even more mass associated with that extra gear included in that "input gear train".

I know and practice heel and toe in down shifting if doing so to slow in a hurry, but sometimes I just let up on the gas and gently apply the brakes and when road speed brings RPM down near 1K and I'll find a lower gear if making a turn or stopping, etc. If someone pulls out in front of me or an animal jumps out, I likely just clutch and brake hard and look for steering alternatives if viable and consider a lower gear selection.

So after having given all this some thought and putting it to paper (so to speak), I am hereby reconciled with the simple truth that these internal shift rail 5 speed and 6 speed transmissions with wide ratio spreads to chase higher MPG while still offering decent performance will never shift like the old Muscle cars did .... "no way and no how".

I am perfectly content to use the habit I learned so well driving that '71 Thomas 66 pass school bus (Chev C-60 / 366BBC / Clark 5 spd) in a city built on 7 hills known as "The Hill City" .... or those several "Dentside" Ford F-350 4 spd Fords my boss used in his U S Mail contracts and that seemed to work well with those two mid '70s Toyota Celica GT and mid '80s Mustang GT transmissions (and even seems to work well with wife's 5 spd Forester, even though it is lighter and some easier) ...
... and now with this Mustang's wide ratio 5 spd. ... that would be more akin to a truck transmission "back in the day" .... but I would not trade the TR3650 with it's slightly annoying (at first) notchiness for a old school T&C top loader or NP A-833 or Muncie considering the 16-19 mpg highway mileage that would come with it .... (but slip in an auxiliary .60 OD unit behind the transmission .... then you'ld have something.)

Andy13186

Quality post


I had a 3650 and didnt have much issues with it, it held up to 100k miles of beating. engine was stock though.

Now i have a getrag mt82 and its nice also imo, has held up fine but has a minor whine that I actually kind of like.

tbear853

Thank you Sir.
Oh, I don't doubt it's toughness.
And I know these can be shifted fast, but not as effortlessly as fast as those old ones,
Perhaps I was spoiled?