I know this question has been asked time and time again but I'm am extremely confused by the research I have done so here goes the question again tho I feel my case is a little different. My dad has owned this 89 Iroc T5 since 92. Was his DD then let it sit in the garage and eventually jus abandoned it. What I've gotten from the searches I've done is don't drain/flush because the old oil helps keep it together, to just top off. Well aware of the myth I'm sure but That applies if you don't know the Maintenance history of the car and is high mileage right? The maintenance obviously hasn't been done in over 8 years but it also hasn't been driven during that time and it only has 66k miles.

What should I do? Jus top off or drain and flush?

Also I wanted to do the same with the rear end, any advice/help there?

Last and final questions what fluid do I use for both? Diff additive? Weight and brand? I went to autozone and seen this Lucas transmission fix with ATF conditioner, recommended to mix or no? I see a lot of ppl saying go synthetic and many more saying not to. Any help is appreciated

 

Run it in the driveway and go thru the gears after changing the fluid with Lucas conditioner. Don't actually move it just keep your foot on the brake to circulate the oil. Since it has sat so long you may have a leaker. Seals dry up and tend to leak if they sit for long. Namely the front seal of the trans. Use what was recommended which is regular dexron. Skip synthetic if its gonna just be a daily. That's just my 2 cents. I've had the best luck that way.

 

The car is up and running already. I've been working on it for the past month and it's constantly being turned on. Thank god there are no leaks anywhere, really clean under the car, jus he usual spider webs and whatnot. I jus want to make sure the fluids are topped off so I won't have a disaster. So flush and mix with Lucas for the tranny? What's about for the rear? What fluid and posi additive? Is changing the fluid completely gonna have a negative effect later on like I've been reading on other threads? That's what's really been confusing me the most.

 

An 89 T5 doesn't benefit from leaving the fluid alone. Use cheap Dexron III and change it every 20k. It's cheap.

And the "leave it in so the bands and clutches work from the old clutch dust" is for the most part, an old wives tale.

 

Ok so looks like I will be flushing and filling with dexron III. How many qts should I buy? Would yu recommend adding the Lucas conditioner or no? Also I've been continuing my research and 80w90 with GM diff additive looks like the way to go. So Should I flush both out or jus transmission? And how many qts does the rear take?

 

Oh jeez my apologies. I didn't even see it was a t5. Throw my advice out the window. That was a automatic I was thinking of. The rear, use the recommended fluid. Whenever a car is put back in service from a non use state, all fluids should be serviced. Cheap insurance.

 

T5 is auto trans fluid, Dex III and the diff uses 80w90, the additive is only if you have limited slip, although i guess it wont hurt anything if you put it in an open diff.

I'd go through and change out all the fluids to avoid any sort of moisture contamination, even bleed the brakes. You dont want any sort of brake failure.

 

Thank yu all for your responses. I'm going to jus go ahead and change the fluids. 5 qts of dex III and 2 qts of 80w90 with GM additive. Lucas tranny fix, worth it or not? Have any of yu gents tried it? Also what's with 80w140? And any brands you guys would reccomend? I'm getting the autozone brand for ATF but what should I go for in the rear? I was eyeing Castro that has additive already, also RP was on the shelf, experiences and recommendation?

 

The Lucas is more for auto trans. No need for it in a manual.