Hey guys i'm new with this site so bare with me here. I'm in the middle of building a 355 for my 85 IROC. It has the t-5 trans, but i dont belive it's the world class transmission, even if it isnt, what kinda of power can it handle? Like whats the limit you would put to it? Also it still has the stock open rear with 3:23 gears. Now correct me if I'm wrong, but dont I have a 3 series carrier? And what spline axles do I have? Someone I know has a posi unit that will fit my rear, it's the GM eaton gov-loc, now i've herd alot of good things about this unit, but then i've herd alot of bad things about it.......Is it good to use? I plan on having my motor push out around 400- 450 horse, will that unit last? Will the posi unit from a 4th gen camaro fit in my rear? If so how good are they? I know they are probably 28 spline axles, can I just swap them out as well? Sorry for all the questions, But i'm sure I will have more. Thanks

 

if you search you will find all your answers, but i'll answer some, i have a world class t5 behind my supercharged 305, it made 381hp and 400ft/lbs at the rear wheels, i dont trust the transmission it's only rated at 300ft/lbs, yours is around 270ft/lb's, i just broke teeth off my ring gear cause i'm running drag radials, the posi units and the whole axle will change over but you have to change your axles, as yours are 26 spline.

 

Stay far away from the Eaton Gov-Lock. They've been nicknamed the "Grenade Lock" for a good reason. The way they engage by centrifugal force causes a major shock load to the unit and causes them to literally explode under decent power, especially on pavement. They work okay on trucks because being in the dirt softens the impact when they engage. If you have 3.23's, then you do have a 3 series carrier already. If you get set of axles from a 90-92 f-body ten bolt, you'll have the correct 28 spline axles to run a 4th gen posi unit. You can also find a used Auburn posi unit that's 26 spline from about 87-89 f-bodies, although they're not a whole lot more durable than the gov-lock units. Although they're expensive, the Eaton clutch style posi units or the Auburn Pro Series units both hold up really well. If you can locate a used Zexel-Toren unit from a 98-02 f-body, they also hold up pretty good and don't cost as much as the Eaton or Auburn units. Although the T-5's aren't known for being very durable, it heavily depends on your driving style. The best advice for getting a T-5 to last a while is no major clutch dumps from a standing start and no powershifting(i.e. shifting without the clutch). To beef up your ten bolt rear, I'd highly recommend using a solid pinion spacer instead of a crush sleeve, an aluminum rear support cover, and welding the axle tubes to the center housing. If you go with these guidelines, you should end up with a fairly durable drivetrain setup.

 

Wow, didnt realize that the Gov-lov was such junk. I will probably go with a 4th gen posi, if I cant find a really good one I will probably just buy one from eaton. The car will be my daily driver, so it's not like i'm going to be dumping the clutch 24/7. And when you say no MAJOR clutch dumps are you talking none at all or just not at a higher RPM? Beefing up the rear wont be a problem. Also I have a set of solid motor mounts laying around, can I use them on the street? Or will I be at risk of breaking somthing or cracking my tranny case? Also I was talking to someone that was running a t-5 in their 84 firebird pushing out a little over 400 horse, he told me that the tranny will live behind 450 horse but dont ever miss a gear if I decide to race it or it will blow to shreads. Thanks for the info guys!

 

Also about the trans, Mine has Borg Warner stamped on the side, Were all 5 speeds Borg Warners?? Thanks

 

All the factory five speeds in thirdgen f-bodies were made by Borg-Warner. The only difference is whether it's a world class unit or non-world class unit. Non-WC units were offered from 83-87, WC units were offered from 88-92. As far as your question about clutch dumps, the simplest way to explain the problem is that the T-5's don't handle shock loading very well at all. When you drop the clutch hard at a higher rpm when the car is standing still, it gives a major shock load to the drivetrain.