We had some 3.73s put into a car yesterday. From 2.73 to 3.73. To adjust the speedo the shop had us pay for a JET SC200 or 2000 that is supposed to change the speedo for gears and/or tires. The shop installed this as well and when we picked it up, we were told that the transmission will be a little funny for a while because the computer has to relearn everything due to the little speedo adjuster. The car takes FOREVER to shift and if you get on it hard enough (only did this once), around 65-70 the rpms max out and the car won't even shift just kind of cuts off right there. We were told to just drive normal for a week and if it didn't fix itself in a week to take the car back to the shop and they'd tweak it some. The shifts are also firm as hell, as if a shift kit had been installed with the gears, but not every shift like a shift kit, just mainly 1st-2nd and 2nd-3rd. If you get on it in first, it goes the same speed as accelerating slowly because the rpms build up the same before the car will actually shift. Maybe I'm just paranoid, but it seems kind of strange, like it shouldn't be like this. Anything we need to worry about, or just drive the car around and let it slowly work the kinks out on its own?

BTW, car isn't a C4, it's a 1996 Z28, but I had to post here because we all know in the f-body section I'll get like 1 reply every month. So respond before they move it please!

:flag

 

I would have the shop remove the Jet part and refund your money for it. The car should have no problem shifting. Hypertech makes a programmer that you can use to reprogram a number of things, including the gear ratio. I believe the programmer is available for '96 and up vehicles. If your ecm isn't programmable(I don't remember what year they changed it, but it's right around '96), a custom burned chip should solve the problem.
Good luck, and I used to be an F-body guy too, my last car before the Vettes was a '97 T/A.

Chris

 

I did this same mod on my 96 Impala SS, it has the same PCM as your Z28. As stated above, I'd get a refund on the Jet module and buy a used HyperTech. Another option is to use PCMforless.com. He can reprogram your computer for ~$100.

When the shop claimed "the transmission will be a little funny for a while because the computer has to relearn everything due to the little speedo adjuster" I knew they were full of it. I've done a gear change on two 96 LT1/4s, they both have the exact PCM as your 96 Z28 (with different software). One was a stick, one was an auto, both worked correctly immeadiatly, no "training" needed. I still use the HyperTech on the auto LT1. On my LT4 I used a HyperTech (worked fine), then I went with a local guy for a reprogram....

Eric

 

I'm pretty sure the '96 has a 4L60E (E for electronic) transmission, which is computer controlled. If that "Jet" thing is only a speedometer correction device, the ECM probably isn't getting the proper info. I think you are going to have to have your ECM, CPU, or whatever they're called in'96 "flashed" to reflect the gear change. Good luck, and...

RACE ON!!!

 

Can any of these things be had for $150 or less? This is how much we paid for the JET product. The shifts actually have improved today I was told, but I haven't gotten to drive it yet today. Should we wait it out a week and then confront them just in case? We can't really have the car out of commission any more, it's my g/fs only mode of transportation besides me taking her places and I've got school and other obligations.

A friend of mine who's an aspiring mechanic says he's heard of this, but all the computer had to do was relearn shift points?

Also, the guy at the shop told us that he has used one of these before and it did the same thing, but I dunnnooooooooo :skep:


[Modified by BowTieBlood, 3:55 PM 1/31/2004]

 

:iagree:
That's what I was getting at. You put it out a lot simpler.


Chris

 

OK, here's the information on the JET device:

JET SCU 2000

1996-1999 Camaro/Firebird 1996 IMpala SS w/ 4L60E

Here are the steps (summarized):

1. disconntect battery
2. locate fuse/relay center under the hood
3. mount the scu2000 on the fender well
4. attach black wire from scu2000 to a suitable ground
5. route wiring harness down to the underside of vehicle
6. disconnect vehicle speed sensor (VSS) harnes, located on the tailshaft of the tranny on passenger side
7. pluge stock harness into the scu2000 harness
8. connect other end of the scu2000 into the vss tailshaft connector
9. connect the red power lead, using the brass fuse adapter to right/left door headlamp fuse
10. recheck wiring
13. move on to "setting and adjusting"

note: if your vehicle came with a factory speed limiter, here's how to remove it... blah blah blah

then it shows you how to adjust it by choosing stock tire size according to the "switch position", then goes on to stock gear ratio, and then the modified settings... it has little switches you turn or flip to choose certain options

That's basically it.

 

Just went outside and checked all of the switches. They all appear to be right on, the tire one I'm not sure of as size in their calculations in the manual come out to 25.65 and the choices are 25 and 26, it's set on 26, but I don't think that would screw with the tranny :(

 

Spend the extra money and get the hypertech to flash the ecm. I've seen it work in several vehicles. I don't know anyone who used the Jet part.

I think the Hypertech goes for about 250 or 300 new. I guess maybe us Vette guys are a little jaded, being used to paying high prices for things, but we know that there's a right way and a cheaper wrong way to do stuff.


You could also find someone who's already got the hypertech programmer for your year and have them flash your computer. I don't think the program holds though if you disconnect your battery for any reason.
Chris

 

I've had a programmer before (on a '97 Trans Am), I will never buy one for my Corvette :D , but the thing is the Z28 is NOT my car, it's my girlfriends car and she can't afford a Hypertech at this time, the limit is basically $150. All we would use it for is the gear swap until we had engine work and custom programming done anyway. About the disconnecting thing. On my Trans Am everything worked fine, you just can't use programmers between cars without erasing the VIN, and even then it screws up sometimes. I sold it a while back to another forum member and it isn't/wasn't working right and Hypertech wouldn't do poopie to help us out.

 

Just go to a dealership and buy the technicians a 6 pack to fix the gearset program...they will flash it and you'll be out the door with a good running car.

(Thats what my friend with a 95 did...after he did gears/LT4 hot cam/exhaust work...basically, the car ran like crap when he drove it in...and after it was flashed it runs 12.8's and idles smooth)

I'm telling you...a 6 pack and some sweet talking to the tech will do it everytime.

 

OR! Simply humor the shop. Wait a week. When it doesn't straighten out, tell them. If they try to clip you for more money, explain that you bought, (from them, right?) everything they told you you needed. You paid their bill, right? "It's supposed to work!" After all, THEY'RE the experts. Right?

 

I like your idea.

Chris

 

yea, that jet module is crap. Either pick up a hypertech 2nd hand ($150 or so) or have a REAL shop do the tuning with a laptop.

btw, if you have more fbody questions.. http://www.camaroz28.com excellent site.

 

Well, I wrote JET an e-mail to see if they had a solution, and if that comes of nothing, guess I'll wait a few days then go complain to the shop. Any of you have a programmer for a '96 F-body you wanna give up cheap? :D

 

Sorry, I don't. I didn't have my '97 T/A long enough before going overseas to buy too many things for it.

Chris

 

It's all good, you keeping up with the post is more than enough help in my opinion, just figured I'd ask JUST IN CASE someone had one, might be my lucky day.

Also, I went to the JET site a little while ago, apparently the device messes with shift points or something as well :skep: but it doesn't have any adjustments for them, just says that it modifies them via everything else.

 

I had a 97 Camaro Z28 & I bought a Hyper-tech when I went to 4.10 gears, with the Hyper I was able to correct the speedo, but also turn on the fans for a 160 thermostat, & adjust shift points, I also could set it for FIRM shift or leave it stock..

I think Hyper-Tec is a good deal for these items, but if you do a cam change then you need to send the comp to be re programmed..

Oh.. BTW When I sold my 97 Camaro I removed the Hyper program, & installed in my 96 Vette. & it worked like a charm on both cars.