Running engine in Neutral with no transmission oil
 

Hey guys, Ive been working on a s5 tII engine swap into my 79sa. I have the engine t67 turbo, greddy FMIC, as well as the 1991 front crossmember and suspension all in. I have brought the whole 91 engine harness with the original ecu as well as the piggyback hks fcon and a greddy fuel controller into this car for now.

I finally got the car to crank today;however, because I have no driveshaft yet, there is no oil in the transmission. I ran the engine for about 10 seconds today and it is idling high, at about 3000rpm, but im assuming that will settle down. Is it okay to run the engine with the gearbox in neutral with no tranny fluid? its a 5spd manaul by the way, and there is a new clutch in it but I have not yet attached the lines...

Thank you guys!

i wouldn't recommend it, gears are still spinning in there

Don't do it....

This thread explains why you shouldn't.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/running-engine-neutral-no-transmission-oil-906040/

So you asked after you already ran it? Prepare to find metal shavings in the gearbox. With the clutch hydraulics disconnected, the engine and transmission will turn together.

http://auto.howstuffworks.com/transmission.htm

I know it's exciting to get a car up and running and all but do try and not fuck up stuff by doing amateur shit like spinning a dry transmission.

Uh oh, thats what i figured, it only ran for maybe five seconds before I shut it down. Thanks for your help guys!

Alright, sorry for the double post by the way, but now I know, right after I cranked it I thought of it. The engine only ran for 5 seconds. Now I guess I will go pump some fluid into it

While we are on the topic, what is the best fluid for this transmission? thanks for your help!

Even though the transmission is in neutral, the input shaft is still spinning and the gears in the transmission are always mated together - meaning the gears are always touching and turning. The only thing that disengages are the synchros. I guess theoretically it would be ok if the clutch was disengaged, but still wouldnt do it. 5 seconds - more than likely you're ok.

I run a mix of redline heavy shockproof and mt-90.

Trans won't turn if the clutch is depressed, and kept to the floor.

it actually will but not much.

It will turn a bit. Have you ever had the rear of your car jack up and ran the engine before? The wheels spin even in neutral.

If the gears have had fluid on them recently (not a fresh rebuild) that should provide enough lube to run the engine in neutral. I've done it a few times with no problems. I've even had to move a car from the driveway into the garage (about 20 feet) in a big pinch with no fluid and 30,000 miles later it still ran fine.

In neutral with the clutch engaged, the trans input shaft is spinning and in turn the motion can cause the wheels to turn, but with thedisc disengaged it better not be turning, that's what the pilot bearing is for.

If you put transmission fluid in your manual gearbox you are just as stupid as running a transmission that's bone dry.....

TII gearboxes are tough though. If it only ran for like 5 seconds, it shouldn't have hosed the gearbox much if at all considering there was virtually no load and there should have already been a thin coat of gear oil on all the gears. Wouldn't worry about it too much.

Transmissions are the weakest part of a dsm. I ran mine at 140whp bone dry for a year and for that year i beat the absolute shit out of the trans trying to break it because the synchros for 3rd was bad and the ones for fourth were on their way out. It didn't have any leaks, it was just dry when i got it and didn't notice until after it blew and i pulled it to swap a fresh-low mileage unit in. If it could take me drag launching my car like a retard from 6500rpms every chance i got being a ricer, your trans should take 5 seconds of low/no load run time.

thanks for the help guys. I filled it up today, It took 2.5 litres, that sounds about right hey?

On all of my cars I mix 2 quarts 80-90 and 1 quart ATF. All Royal Purple.

Should be fine...just don't do it again. :lol:

yup. sounds almost exactly right.

dont forget to put oil in where the shifter goes. dont fill it to the brim, just fill it enough to cover up the square thing.

there is enough friction there to turn the input shaft, not much but it moves