anywereiroam

I bought a 95 z28 with a blown lt1. So I decided to rebuild it with forged rods, forged pistons, ported heads, lt headers with intentions of a power adder.

I finally got the car running and the transmission is crapping out. It does not shift at wot. Revvs up high and the fluid smells burnt.

So it is in need of a rebuild. Now my concern is if i plan on a power adder am I better of switching over to a th350? one of the reasons is it's a lot cheaper to build and reliability. I drive the car to work which is 5miles round trip. Other then that I would just be using it to attend car shows, track, and those late night highway runs. I am shooting for more then 400whp.

Am I better of switching over to a th350 that is properly built. I know I'll lose over drive and kill my mpg but I did not build this car for fuel economy. The car will be driven hard!

Or save up some more and stick with the 4l60 and have it rebuilt?

93M6Formula

If you want to go with a 3-speed, I would much rather do a TH400.

SwampWS6

iTrader: (7)

IMHO a TH400 will eat up a considerable amount of HP. Especially because his goal is around 400rwhp. To me a 350 will be a lot better if you are doing track more than street. a 350 eats less hp than a 4L60e too. 350 has pretty gearing as well. But as far as highway runs you should stick 4L60e

anywereiroam

I also thought maybe it would be cheaper to rebuild the 4l60 myself? Download a step by step guide and try it. I've never rebuilt a transmission but I figured I have to learn eventually. Unless I should just send it out.

96capricemgr

iTrader: (1)

With only 400rwhp at the dragstrip you are still going to need gearing for a hard launch, with a TH350 you get less first gear multiplication and no lockup meaning you are going to probably keep the stall lower again hurting launch.

For a 5mile commute I wouldn't worry about OD but the lack of lockup causing conservative stall selection is going to suck.

If aiming for enough power that the 3.06 first gear of the 4L60E is not an advantage then I would be quicker to consider a TH350.

My car would not be anywhere near as quick with a TH350 because the 3.06first/4.10axle /3800stall are what make the 1.5 60ft happen. With a TH350 I would have a lesser first gear and likely run less stall, endup with 1.7 60ft times and barely be in the 11s rather than being at the point where I have to consider a rollbar to go any faster.

People focus on the OD being the only major difference with the TH350, I just want to point out the other two big factors so you make a decision on more complete picture on the potential minuses.

If I were building a fast NA primarily track car I definitely would consider the TH350, easier rebuilds lots of trick liteweight parts etc. the first to second ratio difference of the TH350 makes it easier to keep the engine in the powerband too. With a 4L60E you endup overrevving first a little to keep the rpm up going into second.

bowtienut

iTrader: (1)

I'm reading this as you want something to cover a power adder setup which should be FAR in excess of 400 whp. Keeping a 4L60E behind that won't be cheap nor trouble-free.
So, then it depends on priorities. Are you willing to spend the money every season or two to keep a TH350 behind a healthy power adder setup just to go .1 sec quicker, or would you be okay with giving up that tenth and going with the extra durability of a TH400 that almost anyone can build?
I don't see anybody going really fast with a TH350 and doing it cheaply.

If only 400 rwhp is your target, then I'd just get a QUALITY-built 4L60E.

I agree with 96caprice; for any converter you would choose to run good ET's, the loss of lockup is a bigger deal than loss of the overdrive ratio.
What rear gear ratio will you run?

anywereiroam

Right now I currently have 3.27. But I think the 400 is going to be my choice. I'd rather have the durability. I'm not a serious racer I just want to have some weekend fun. I'm going to assume that cost wise it will cost me as much as it did when I went from the 700r4 to the th400 in my third gen.

bowtienut

iTrader: (1)

It just dawned on me that you're probably running the little 7.6" rearend. Any plans to change that? If not, then I don't think the 4L60E would be your weak link.
3.27 gears and non-lockup are gonna suck; and until you get a power adder on there, will also be slow without the deep 3.06 gear of the 4L60E

anywereiroam

Yes the 10 bolt will be replaced for an aftermarket. My plan was to start from engine, to trans to rear end before any power adders, unless I'm looking at it the wrong way. I've never built a car for this sort of thing so I'm sort of trying to see if I'm headed in the right track.

Shownomercy

iTrader: (1)

Put a glide in it.