Started up the Vert for the first time since completing the 5-speed tranny swap. Let it warm up, pulled it out the garage and.... OMG, then I remembered I forgot to fill the transmission with gear oil!!! I shut it off and pushed it back into the garage. Did I do any major damage by letting it run for 10 minutes and driving it 20 ft out of the garage?

 

i drove 2 miles daily for 6 months before finding the drain plug missing., you're good.

 

Thanks.

 

i wouldn't say that, but you may be alright.

 

I drove 230mi with an empty trans.

I did similar with an empty diff, too... that was less happy than the trans was Hypoid gears make a lot of heat.

If you want scary, a friend of mine dolly towed his Miata (same transmission) for 800+ miles each way. No splash lube with the engine off, just the output shaft spinning in the gears and the driveshaft running on the already-fragile output bushing... Somehow the trans is fine but I know if I tried that I wouldn't be so lucky.

 

there's nothing wrong with towing these cars if it is filled. i dolly towed my TII 2500 miles and it was perfectly fine.

a friend dolly towed his FB 20 miles with the diff unknowingly empty and it promptly seized up.


but even idling a manual transmission without oil can be a crap shoot, if it survived then you should be good but it only takes a sloppy bearing or debris left over to cause major damage when running dry.

 

What lubes the bushings? When I pull my driveshaft, no fluid comes out, so the fluid level is below the bushing height let alone shaft height. The only thing turning will be the shaft in an ever-dwindling oil film on the gear bushings left over from the last time the engine ran.

Mazda recommends no more than 50mi/50mph, for what that's worth.

Flat towing is half the reason I wanted to go with a floating rearend. Pop the axles out and it's good to go.

 

i have tried dropping transmissions without draining them at the same angle i tow on a dolly. what happens? i have a half quart of stinky *** smelling oil running down my arm into my armpit.

no, they do not run dry unless you are towing the vehicle with a tow bar, which is something i would not recommend for more reasons than just the bushing issue.

 

i tow dollied mine as well 700 miles. not dry this time.

 

Why yall hijack my topic?

 

i thought the topic was about what possible damage there was in running the tranny dry

 

Thats funny.

 

The gears don't like it much but they manage, the synchronizers also don't like it much but oddly enough they seem to work better after refilling, like the glaze gets broken. The bearings deal okay, the bushings that the driven gears ride on tolerate it but they get a little loose.

The tailshaft bushing hates it. When the tailshaft bushing goes loose, there's not much holding the driveshaft "square" and you can get weird driveline vibrations that go away if you lift throttle and reapply.

AFAIK the only way to get RX-7 tailshaft bushings anymore is from a good used trans. In theory the Miata part may work but I haven't tried. Usually when I fry one of those bushings, the rest of the trans is also pretty worn if not actually broken.

Bad tailshaft bushings also can damage the driveshaft yoke, which will hurt the new trans. Check it for grooving and wear (wasp-waisting).


You probably didn't hurt a thing driving it only 20 miles.