Well I have a 89 IROC that was converted to a T5 from a 83 Z28 or some 83 V8 f-body before I got the car (let me tell ya, it is a nice hack job!). The crackhead mechanics that did the swap used gear oil instead of ATF. Sometime before the nationals this weekend I'm going to make an effort to change the fulid. My question is... Since you cant posiblly get out all the gear oil without taking the trany apart, will there be any ill effects of the residual gear oil mixed with the ATF? Thanks. Kat

Works fine. I have run that combination in may transmissions before, half & half gear lube and ATF.

If it's a 83 T-5, it's supposed to have gear lube anyway, although either will work.

i'd run gear oil and not atf in it, i use amsoil or M1 gear oil with no problems in wct5s

RB83

you seem to know alot about the T-5's so heres a question, the one in my 82 is from a 1987 Z-28, or so the seller said, its a second gen case, and is NWC this I know for sure, many have said gear oil many have said atf, I used ATF, tranny is a little notchy going into gears, but doesn't grind or anything like that, been a long time since Ive driven a T-5 f-body, does this sound normal or should it be real smooth going through the gears, but thats not as much of a concern as the proper lube in it, Ive heard gear oil in a atf recommended tranny can wipe out the syc's and vice versa, any truth to this, so what should mine take, I used I believe dextron 3

What weight do you reccomend? I have a 91 WC T5.

i'd have to look to be sure, but i think my amsoil and M1 are the same, 85w-90

I look at these threads pertaining to what fluid to use in the older non-WC t-5's, and I first started out using 80w-90 lube in mine.
If the weather was cooler than 50 degrees outside, My tranny would be difficult to shift in every gear until around 30 minutes of driving. Then it would slowly start shifting smoother.

Before I say anything else, I should say this:
Both ede and RB from what I've seen and read on the board, are very knowledgable on the topic of third gens, and cars in general, and they have given me great advice in the past. And I appreciate thier help.

On my tranny, (original BW) I tried every Z-bar adjustment, changed oil twice, etc... and it still would not shift correctly when cold. I finally got fed up and called Gearzone.net on the phone to order an overhaul kit. Once the guy found out I was using gear oil, he recommended not buying the kit and putting the right oil in it first.

I said, what do you mean "Right oil"?? He said ALL T-5's should use Dextron III, whether it's a NWC or WC. Well, I doubted him due to what I've read here, and asked him if he could look it up and I gave him the numbers on my tranny. He called back and said "Yep, should be Dextron III!"

I now use it, and it made a world of difference. Now it shifts smoothly whether hot or cold, and the only grinding I have now is from a P.O.S. throwout bearing I have to replace. But that didn't start till way after this. Maybe either oils will work, but not in my case. Just my experience. Hope this helps!

BTW.....as RB says, matbe the right combo of gear oil and ATF would work better. Haven't tried that yet. The viscosity of straight gear oil though, didn't work for me.

like i've said all i've ever used is synthetic gear oil, which looks a lot like 20w motor oil. i've never had a problem, nor have i had trouble shifting due to the cold thick oil. i know my experience is limited to just a few transmissions, but i'm slod on amsoil or M1 gear oil for manuals.

Yeah ede, that makes sense. If it's a thinner oil I think it would work fine.

I've heard Amsoil is top of the line stuff. I forgot to mention that they highly recommended Mobil-1 synthetic, which he says is even better than Dextron III. Still quite a bit pricier though...especially if your speedo to tranny connection leaks like mine.

OK, I looked on the Amsoil website at their gear oil. Would the AGL 80W90 synthetic be the one I want?

I would use GM 80w90 gear oil. I wouldn't recommend any synthetics.

Talk about back from the dead! Check the first T5 thread at the top of the page for more info.

JamesC

You are right jamesc this thread is 5 years old, but it appeared under the "NEW POSTS" section... weird.

ATF. If you had gear oil in it before change it a couple of times. It'll shift better.

And BTW how'd that work out? It's been a few years so I guess you got some miles on it by now, lol...

holy crap this is a old post..

That was two t5's two t56's, 700 and another car ago. lol And yes it worked well for the few months the t5 lasted before it commited suicide