I just bought an 85 IROC-Z with an original T-5 and a replacement 350.

The T-5 works fine under normal driving conditions and even under full throttle if i dont engage the clutch too harshly. If I try to power shift it though, it acts like the clutch doesnt engage at all. I have to shift it back to N and re-engage 2nd and it grabs fine.

Now i apologize ahead of time for my lack of experience. All my hot rods to this point have been autos so im learning.

Any suggestions? Im sure its something obvious to someone with more experience than me


On another note, if the trans needs rebuilt, will a NV3500 fit? I have one i have been sitting on for a V8 s10 project i havent gotten around to.

 

anyone know if the NV3500 will fit?

I know its the same size from bellhousing to tailshaft as the t5 in s10 trucks, and the shifter is in the same location.

 

If you do manage to fit the NV3500 in, it's not designed for a car or race shifting. It's a med-strength truck trans with gearing to match. Rebuild the T5, or complete a T56 swap..

My $0.02

 

Id love to do a t56 swap, the trouble is finding one cheap

 

First, you cannot powershift a T5. All it will accomplish is a broken trans. You will mostly likely blow 3rd gear and/or break one of your shift forks. It sounds like something is already half fragged.

I agree that the NV3500 is not a viable option for several reasons. No readily available crossmember and not TA provisions are two that come immediately to mind. As stated, this is a truck trans, and even if you could get it in there the result would be lackluster.

You've got a couple options, the cheapest of which is to pull your T5 and get it back into tip top shape. It will be fine as long as you do not abuse it (read: no powershifting). Your other option would be to swap to another trans like a Tremec or a T56, the T56 is the darling of the dance (and the reputation is deserved).

You just have to redefine your definition of cheap. You're not going to find a T56 for under $800, and $1,200-$1,500 is more like it. However, you have to consider your alternatives. A Tremec TKO500 is going to cost you about $2,750 once you add in all of the other required swap parts (TA, etc.). A T56 swap can be done for maybe a little less, say $2,500 depending on exactly which parts you use. The bottom line is that a tough manual trans is not going to come cheap. The old hot rodders addage will always apply: "Speed costs money. How fast do you want to go?"

 

First off thanks for the advice.

No powershifting a T5 huh? Its gone!

So T56 then... i have read up on this swap here. Looks like an LT1 T56 is my best bet since ill probably be using an old school 350 w/ a 2 piece rear main seal (Just because i already happen to have an early casting in my garage and the high nickle will be a great plus when i put nitrous to it)

How much can a T56 take? Im planning 450-500lbs before a 150-200 nitrous shot.

Also, i might be scoring a 94 LTI car. Is the rearend a direct swap to our 3rd gens?

 

The LT1 T56 is officially rated to 450 lbs/ft. by Tremec. My experience is that they can take a bit more. If you want to be safe there are several upgrades that you can make to a T56 to get even more power handling ability. They can be built up to 800 lbs/ft. If you plan to drive hard I would advise doing billet synchro keys, brass fork pads, and a steel 3/4 fork as the bare minimum of upgrades.

For your 2-peice RMS engine you will need a custom flywheel. Prepare to spend about $370 for that part alone. McLeod and Centerforce both make them.

A 4th gen LT1 car's rear is the same 7.625" 10-bolt design found under our 2rd gens. It is a bolt in, with one but. But, the rear is about 3-4" wider than a 3rd gen rear and if you use the stock 3rd gen wheels it will push the tires out past the wheel wells. This looks bad, and is also illegal in every state to the best of my knowledge. The solution is to use wheels with a different backspacing.

 

wow, thats a pricey flywheel. I might just be better putting the LT1 in, since it is complete and the 2 piece RMS engine is in parts.

Hmm time to research the computer headaches of an LT swap..... i wonder how much nitrous i can pump into an LT1 before stuff starts breaking

Getting this plan down before i start the work is really gonna cut down on the headaches later, thanks for the help.

 

My guess is no more than a 100HP shot. The LT1s have hyperuetectic pistons and they do not like spray. If you really want to run the giggle juice upgrade to forged slugs and gap the rings accordingly. Otherwise you'll just end up with a very fast grenade with an unpredictable fuse.

 

Thanks alot for the input TKO, i have alot to think about before i tear this car apart hehe

 

That's always the best course of action. Remember that a failure to plan is a plan for failure : )