T5 trans fluid?????

[AV8Paul]

Flat Ernie mentioned in another thread that nwc T5's used 70 wt trans fluid and wc used dextron. This is the first I ever heard of that. True? I have my nwc T5 filled with Dex III and have been driving it around. What's the real story? I don't want to screw up a fresh rebuild.

[Cshabang]

I've always filled them with ATF Paul, when I was a tech at ford, and my own. I tried gear oil in one, shifted hard, and it got real bad when it was cold-for obvious reasons...my .02

[Bugman]

So will regular gear oil in a T5 cause any real problems, or is it just a drivability/shiftability concern?

[Kustm52]

Gear oil won't hurt it... I've added 90w to a really worn out one just to take up the slack.. A tran rebuilder here locally always used 20w50 in his rebuilds... he said the atf was just too thin.

Brian

[Cshabang]

no problems that I'm aware of.

[Flat Ernie]

Flat Ernie mentioned in another thread that nwc T5's used 70 wt trans fluid and wc used dextron. This is the first I ever heard of that. True? I have my nwc T5 filled with Dex III and have been driving it around. What's the real story? I don't want to screw up a fresh rebuild.

You can run ATF in a NWC T5 - I did it for years.

The reason for the change was the construction of the transmissions. The NWC trannys use bronze bushings & solid brass synchros - exactly like an early Ford trans & why they originally called for light gear oil (70 wt). An old Mustang racer's trick was to run 40 wt motor oil for quicker shifts - but these were gone through regularly & quickly abandoned when the WC trannys came out in '85...

The WC trannys use needle roller bearings & carbon-fiber blocking rings in the synchros - the gear oil is too thick to allow these to function properly - hence the change to ATF.

If you run ATF in a NWC tranny, it will probably wear prematurely, but the life of the tranny will still be measured in tens of thousands of miles, not hundreds or thousands.

One of the biggest killers of T5s is end play, however, & the materials used are identical in both WC/NWC (same shims), so those would be unaffected by type of lube.

The other big killer of T5s is overshifting - get a quality shifter with positive stops on it, adjust them per the shifter mfgr's recommendations.

I've had more than just one or two of these open & seen WC run with gear oil that ruined bearings & shafts & NWC run with ATF that suffered little trouble - mainly increased wear on bushings, but nothing extreme or excessive.

Because there are so many flavors of T5s, there is a lot of conflicting/confusing info out there & most do not understand the difference between WC & NWC...

[AV8Paul]

Thanks to all. I was worried about hurting the "new" trans I've waited so long to use. I have plans to put some mileage on this thing as soon as the tropical storm passes us by today. My mind is now at rest about the fluid.

[Flat Ernie]

So will regular gear oil in a T5 cause any real problems, or is it just a drivability/shiftability concern?
Gear oil won't hurt it...
Gear oil in a WC T5 will ruin it.

Gear oil in a NWC T5 is fine - all pre-'93 S10 T5 are NWC.

As for drivability/shiftability, running ATF (Dexron II is the recommended lube) will improve the "shiftability" of NWC T5 with a very slight increase in wear of bushings.

I've added 90w to a really worn out one just to take up the slack.. A tran rebuilder here locally always used 20w50 in his rebuilds... he said the atf was just too thin.

If you've got "slack" in a T5, it's a matter of time before it dies. If it's a WC T5 & you run gear oil in it, it will eat the needle bearings and shafts. It will also shift like crap.

Engine oils are not formulated for use in gear boxes & will result in gear wear. When I mentioned using 40 wt in race applications, remember these were torn down & inspected regularly - they often died because the early T5s were fairly weak.

If a thicker lube is required, I'd suggest Type-F ATF. But thinking ATF is "...just too thin" is little more than misperception. Viscosity has little to do with what type of friction packages are included or required. Automatic transmission gears operate under the same extreme pressures as modern manual transmissions - bottom line: use the type of lube the gearbox was designed for. WC T5 were designed to be used with ATF.

Of note, Tremec no longer recommends gear oil for the NWC, but stops short of specifying a specific lube & suggests following OEM guidance. This leaves a gap where OEM guidance is gear oil...

[392_hemi]

What about using Mobil 1 synthetic ATF in a NWC T5?

[chuckspeed]

Okay -

As the self-appointed king of blown transmissions, this is an area I know well.
Late model manual gearboxes are designed to run ATF - period. engine oil is not formulated to take gear pressure (tooth contact area) which means you'll subject your gears to galling and eventual failure.

Long B4 this happens, tho - you'll eat your synchros. Thick oil (or an overfilled trans) causes parasitic drag within the gearbox, thus increasing the time required to sync the gears between shifts. If you've been shifting the rig like it's still got one of Henry's old boxes - you'll never notice this, but if you ever try to speed shift on a 1/4 run, then you'll buzz the tips off the synchros and foul the blocking rings inna new york minute. Trust me on this - I just cooked a Tremec 3650 (upgraded T-5) racin' a blown cobra last month. One missed shift is all it takes.

On the same subject - synthetic is the ONLY way to go inna modern manual box. Synth does not have the same variations in viscosity due to temp that organic oil does - the result is smoother shifts.

I'm trying out a new synth right now that seems to work pretty good - Royal Purple Synchromax. This stuff turned a notchy box into a slick shifting outfit.