Thread: When is the Non-HD to HD Trans Upgrade Needed

On a car that will never see slicks, a burn out, or a 1/4mile run, but gets driven pretty hard? Talking L32 top swap not turbo here so instant torque. Maybe 275WPH when all done.

There are plenty of guys out there not using the HD diff but you have to be careful with how you drive the car with that much power as any wheel spinning will but a lot of stress on it. The HD diff is just added insurance against failure which even in itself wont keep problems from occuring and common sense is the best advice with any diff in these transmissions. I have seen stock non-HD differentials fail without any hard driving but with a ton of miles on them. Good service habbits and driving manors keep things alive longer. There is no real good answer to your question though, but if it was in my own car I would go with the HD diff if you are looking for those kind of numbers to the tire.

I was hoping you would reply.

So you recommend a complete HD upgrade?

Is a reluctor wheel going to be needed after the PCM reprogram to utilize the stock gears properly?

What year/model car is this for? The differentials both have the same ratio if your current trans has a 3.29 gear, the HD trans changes the ratio in the drive/driven sprockets to accomplish the 2.93 overall ratio and there is nothing special needed tuning wise to swap from one diff to the other. You will need an HD diff, diff housing, bearing and spacer for end of diff, HD output shaft as it is longer, and an HD passanger side axle. I have all the parts for the trans end of it unless you have something lined up already and for an axle you can either ask Ed Morad or buy a new one as they have recently been available in the aftermarket world as brand new-no core charge pieces for around $100

An '01 GT
I just thought the PCM basically gets replaced with a GTP PCM and will have the 2.93 programmed into it, hence needing the reluctor wheel.

Can you PM me a quote for parts please if you don't want to post them here?

I sell the diff and required bearing and shim, housing, output shaft for $250 plus $25 shipping so $275 to your door. Now that I know what you are working with I can give you some suggestions. The reluctor wheels are aftermarket only pieces available from Intense and ZZP if I am not mistaken. They are custom made parts and I have no suppliers for trans parts that deal with them as they are specialty items to this community. Using a GTP pcm is certainly the best route to go with for doing a top-swap and you are correct that the gear ratio will be different and if not compensated your you WILL have trans problems! If custom tuning is out of the question for you I will reprogram a pcm making gear ratio changes only-no engine tweaks for a fee of $50 plus shipping. The reluctor wheel setup is fine to fix the incorrect gear ratio code problem that will be present but I think that leaves you with the speedo being off a bit, so $60 for a custom reluctor and $100 for a speedo recalibrator adds up fast and tuning is the best route to correct the problem.

It will be getting a custom dyno tune by INTENSE so I better get with them and figure out how they do their top swap tunes.

So we're looking at $275 + a pass side axle and thats all that would be needed if the PCM is programmed for those gears? And if not, I'll need to add reluctor wheel to diff and get a speedo recalibrator right?

I just want to make sure we're on the same page here. This is my forst top swap and it's not my car, I'm just doing the research and the install.

never mind i had a stupid moment

Man, and I thought I was the only one thats going to atempt a Gen V top swap on to a L36......When are you doing the swap, cause I may have some Questions for you when you finish

Hoping for it to be in about a month or so. I think I have everything I need but we'll see after it all goes together.

Gen V Eaton M90 blower is what came on the 3800 Series III Supercharged (L32). Gen III Eaton M90 blower is what came on the 3800 Series II Supercharged (L67).