Thread: 1997 Grand Prix GT- L67 Swap question(s)

New guy here so take it easy on me. I have searched google over and over for what I'm looking for, but I haven't answered all my own questions so here goes!

My GT has a bad motor and trans, but since I got it cheap I figured its worth putting my spare L67 in it. I know they are the worst year b/c of the older style wiring that was used and also because of the vacuum controlled tranny. Honestly though, this doesn't seem to be that big of a deal. I'll lay out my plan, you guys tell me why its not going to work!

Step 1 is getting the spare motor back together. The crank and block are at the machine shop right now getting work done. There was some water in the cylinders so we will be going .010 to get it fresh again. Next up will be the heads. I'd like for this motor to last 100k+ miles lol... jk! I'd like to keep the motor itself relatively stock, ie heads and cam. This will probably be my daily for a while!

Step 2 will be getting the fresh L67 in the engine bay. This is where I run into some problems. The L67 is basically the same as the L36 that was in there from an outward appearance. If I'm wrong then please let me know. I'm assuming that the stock harness and computer will run the motor once the computer has been flashed with a tune. I'll more than likely use ZZP or another shop that can do canned tunes to get it running. Later on I plan on finding a local shop to do the final tune or maybe get an HP tuner and attempt it myself. Also, I know that the MAP sensor won't work, but I happen to have a spare GTP sensor so that can be wired in. I'm not really worried about the trac control since apparently there are issues with the 97 computers controlling it anyways. All other things considered we should be good... right?

Step 3 will be tackling the transmission. Instead of doing a complete GTP swap, I've been looking at options for transmission upgrades. I think a 4T60E-HD will fit the bill and there are a couple of junkyard units available locally. I emailed ZZP and was told that a 60E-HD can easily support my goal of a daily driven 300 whp tranny. Since I own a towing company, I have a couple of transmission shops that we do business with. One of them does performance builds also. I talked to this shop about building me a 4T60E-HD for performance and the owner said its no problem. So besides a better built tranny, axles, and a one way check valve to the modulator, what am I missing here?

So there it all is. What do you guys think? Will it work or won't it? I've been trying to do as much homework on it as possible, but I'm just not convinced that I have covered everything. I know it won't be as simple as it seems and I'll run into issues here and there. I've been working on cars all my life and have been a tech off and on for the last 8 or 9 years so I feel this is something that is more than in my range of doing. I want some opinions and help from guys that have actually done this just to cover all my bases.

I just did an l67 swap on my 99 gt and it wasnt bad at all but for the best info I would use John at intense racing. They always answer the phone and if they dont they call you back when you leave a message plus I havnt heard anything good AT ALL specifically about ZZP's tunes. The other thing that I forgot about was the wiring when I did my swap just make sure you order the l67 swap kit from one of the vendors its a little over 40 bucks shipped. Also on the tranny I would look for a 4t65e with 3.29 gears out of a 98 or newer gt or a 4t65 e hd out of a gtp. John can program the pcm for pretty much anything you need. Also make sure and pull all of the sensors out of your old engine with all of the wiring so you have everything to put back in the l67.

I've considered the 4T65E-HD swap many times over. I know many guys sing their praises, but I don't see anything necessarily wrong with just going with a 4T60E-HD.

I have heard they are junk and you dont really need the hd thats just more parts like the bigger axle on the passenger side. The only thing that is hd is the dif not the tranny, think about it they only used it for one year?

Only using it for a year doesn't mean it was junk. It sounds like they had something better waiting in the wings. I read some where that there was only a 5 ft lbs increase in the torque rating of the 4T65E-HD vs the 4T60E-HD. Chances are good that if you break one, then its going to break the other lol.

I can see where being electronically controlled is a big plus for GM, but it doesn't mean the vacuum stuff was garbage. Hopefully some others will chime in too!

Many sets of headers will not work with the 4t60. ZZP's as an example.