I have a '96 LT1/Auto/2.59 that I'm about to get a 3.54 installed. I know that since it's OBD2, the speedo is calibrated through the ECM after the gear change.
My question: There's other things I want to do to the car before it finally goes to a tuner for speedo calibration and tuning. Will there be any driveability issues with the new gearing if I wait?

 

You need to make some phone calls ahead of time. The 96, being a 1 yr orphan as far as tuning goes, suffers from a lack of folks that have the software and equipment to tune them.

When I made calls, it was nope, nope, nope, "If you buy a Jet DST box, I can", nope, nope, maybe, etc.

With that said, with a Jet DST box, a laptop running XP (that is the safest OS to run) it is easy to reprogram for a gear change.

 

Thanks for the input. This?

Heck, it may be worth it just to do it myself and to have the ability to tune-as-I-go.

My main concern is if I get it re-geared, if it will set codes or run weird until it's tuned..

 

No. It will run fine.

 

i have done the same with my 96, i installed 3.07 s no problem, just remember your passing gear will cut out a lot sooner, i bought a hyperttech tuner but which was able to due limited adjustments, now its useless to me because i have now had it tuned by mark mcphail in costa mesa , ca so in order for anybody to use it i would have to reinstall it to reset it, therefore losing my tune, be very careful when playing with your computer.

 

yes, that is it

 

I installed a Dana 44 with 4.11 in my 1994 with 4L60E. Original was 3.07 Dana 36. Before I had the ECM reflashed, the shifts were way off with the 4.11. It shifted at extremely low rms. 3.54 probably wouldn't be as bad. PCM4less told me that my trans could be overheated and damaged if driven extensively without a reflash. IDK. I have an external trans cooler, and I only took it for a test drive before reflashing. Now it shifts like it should and speedometer is accurate.

 

I thought the 95 was the odd year. I see a lot of things listed as 95 being to odd year between OBDIand OBDII

 

I agree, the engine and transmission have no idea what gear you have. The speedometer will read slower then what you are going, but the car will run fine.

When you finally reprogram the car make sure you adjust the speedometer error first and make sure you have the program auto adjust the shift tables so all is adjsusted together.

 

95 has an OBDII port layout I believe, but still is OBDI. 1996 is the one and only C4 Corvette year that has to be programmed with a Jet DST interface, unless you spend big bucks to buy the interface from the guy who wrote the software/build the interface and subsequently sold the rights to Jet.

If you take the time and go look, tuning support ends at 1995 and picks up again at 1997. That is why some folks swap a 1995 ECM into a 1996 ( if you don't have EPA checks) that way there is more software and interfaces available.

 

This is all correct, and yes Jet DST 14005 is the only tuning suite now available to tune a 1996 C4. The 95 is odd in that it has the 16-pin port (like OBD2 vehicles) but still uses an OBD1 ECM. It can be tuned with Tunercat, which is a lot cheaper to buy. But Jet DST is literally Tunercat for OBD2 vehicles.

To the OP, if you had a manual car I'd say just don't worry about it until later if you can stand the speeo reading incorrectly. It wouldn't affect the running of the car at all, I think. But as others have noted, I do think that with the auto it may affect your shift points and the hardness of the shifts. With that big a change in gearing, I think it would be noticeable. I would recommend you just buy the Jet suite and start learning it if you plan more mods in the future. Even if you have someone else tune the car later, you will at least have the ability to read and store the stock calibrations and the revised ones, and then make any changes you want, any time you want.

 

And if you do buy the Jet interface, seriously consider sourcing an older 32 bit laptop running Windows XP, I would recommend XP Pro, but just XP would work.

I can pretty much crash the software on my Win 7 desktop, and it is still 32 bit. I wouldn't at all try to run it on a 64 bit machine, all considering the bad things that can happen if the you get a memory or other exception while applying the updates to the car.

 

I would second this advice. I use a dedicated old laptop running XP.

 

Well, yet another new twist.
I have my brother sourcing an old XP laptop from one of my nephews, so I think I have that covered.
Went to Amazon to pull the trigger on the Jet and what do you know!? They won't ship it to any CA address that I entered!
May have my truck driver buddy pick it up at a Reno address for me.
The joys of living here.....

 

If you go this route, check into and buy a new battery, if available. I read somewhere (don't remember where) that you don't want the laptop being powered by the adapter into a wall socket, and you don't want the battery to crap out in the middle of an update.

What is the price differential, if any, from buying from Summit Racing ?

https://www.summitracing.com/oh/part...model/corvette

 

For another Win XP only program I am using I created a Windows XP Pro virtual machine running under Windows 10. I purchased a Win XP Pro disk for very little money and now I do not need a dedicated XP machine.

 

However that software isn't attached to an interface (and original source code) written for XP that can potentially turn his PCM/ECM into a brick (bricking it). The OP would have to do extensive testing to make sure that the update software part of the Jet package will function while attached to the car/ECM. There is not way to test this without it being attached to a ECM and that is not the time to find out it took a memory fault (32 bit -vs- 64 bit) etc.

I made a living writing software on mainframes, building PCs and generally figuring out how to do things that couldn't/shouldn't have been done. The difference was, I was able to test what I did, except for software I wrote on a contract basis for the May Co and was assured the database they attached it to for testing was a test database, until I saw the manager keeping track of what emp nbrs we were testing with and going in and changing them back.

Here is a write up

https://www.howtogeek.com/228689/how...on-windows-10/

I could have figured out a solution that might have worked, but for the cost of a refurb'ed WinXp, 32-bit machine with a warranty it was just safer to have a dedicated machine. After all, there is no way to test the rewrite portion of the software until you actually try it.

Then you get an update successful message or you experience your own OhNoSecond. You know, the second of time where you go Oh No and realize how bad you just effed up.

Then you are scrambling to find out if someone can bring it back to life, or you start making phone calls to the junk yards/Corvette salvage businesses looking for a new unit.

 

All good points and the counterpoint is that XP hardware is notoriously old/unstable. At work I support numerous platforms in a virtual environment where getting good hardware is difficult if not impossible. When I considered what to do to run my Tech 2 software written for XP at home I figured for myself I felt much better creating a virtual machine and running XP under it. If I turn off the virtual machine all I have to do is copy the files that constitute the virtual machine to a USB hard drive and I have a backup. Trying to backup a Windows XP laptop is not so easy if you do not have the same hardware to restore to. It's too bad that there is no better backwards compatibility, but I understand that MS doesn't' want to support legacy 16 bit software. BTW, I am using VMWare to run the XP virtual machine.

 

Now you have my attention, where did you acquire Tech 2 software and is it bidirectional and still available ? I need a Tech 2 to be able to do some things with my Duramax (and a friends) such as command a relearn turbo VVT position switch (so the ECM/PCM knows where the variable vanes are in the turbo). It doesn't use the old traditional waste gate turbo.

Then:

The danger point is the updating of the CPU in the car, regardless of platform. There is just no real good solution for 1996's.

The laptop I bought has been refitted with a solid state drive (SSD) so, while laptops are supposed to be carried around/moved, it is safer to take in the car while doing data logging.

I can crash the editing software component of Jet DST pretty much at will on a Win 7 Pro machine running in XP compatibility mode service pack 3

Here are Jets instructions

http://jetchip.com/wp-content/upload...uick_Start.pdf

http://jetchip.com/wp-content/upload...structions.pdf

 

I purchased one of the Tech 2 clones as even a used Tech 2 is still very expensive. It came with the software for XP so that I can mirror the Tech 2 screen, playback captures and in theory update the CF card. XP Pro is running as a virtual machine in VMWare Workstation Player.

Does your SSD in your laptop support the trim function, I thought XP wouldn't support that.

I have been supporting Windows hardware mainly for many years and personally find it hard to trust hardware old enough to run Windows XP. Running it on a SSD is sure a good start. With VMWare running an XP virtual machine under Win 10 it supports serial ports and most USB devices. I have always considered MS virtualization a step or two behind VMWare based on using both, but in full disclosure more with VMWare. I was in charge of a project to move numerous Hyper-V VMs to VMWare.