I have everything complete on my T56 swap in my 93 Camaro except for the manual PROM chip. When I hooked up the VSS to the speed sensor and drive the car down the road, I get a ridiculous value at the speedometer. When I am moving at say 10 mph, the car says I am moving at 100 mph. I still have the 2.73 gears in the car until I get my 3.42 rear axle swapped in, but that should have the opposite affect and read a lower than actual speed. Does this mean anything to any of you guys that have done this swap in a 93??

 

You answered your own question. Change out the PROM chip for a manual PROM. My 93 Camaro did the exact same thing when I did my T-56 swap.

 

FuryZ28, I picked up a BDLD PROM for a M6 car, installed it, and now the car is running VERY rich. Did you replace just the PROM or did you also replace the harness and or ECM?

 

Not that I recall...it's been awhile (like 6+ years). I'll have to open up my ECM, but if I remember correctly, I had an aftermarket chip, which I think might be piggybacked onto the OE PROM. I'll get back with you on it...

 

Don't forget the 93 uses a plastic gear in the tranny tail housing that matches to the chip and gives the car its speed (as well as the speedo).

Make sure you have the correct gear. Lots of teeth.....I think the light green one is the one you need for 3.73s.

Perry

 

I guess the 93 A4 still had a speedo-gear driven VSS, neighbour Perry?

93 T56 has a reluctor ring & magnetic pickup VSS
11 tooth in the wide ratio trans.
17 tooth in the 2.97 first gear trans.

 

It does. Really a 700R4 rebadged a 4L60.

The E came out in 94.

Perry

 

Thanks for the reminder. The trans I put in is from a 94, so I have the matching 3.42 gears in a rear end that I am swapping in. I am running stock tire height on my SS wheels so I am hoping that the speedo will be exact or very close. I will save the tweaking for when I go to 3.73's

 

That is correct. I had nearly forgotten the 93 M6 had the close ratio gearbox (same ratios as subsequently used the the Z06 and the Viper, I believe) and given its lower 5th gear used 3.23 gears.

I was able to use any 4th gen as sold rear axle so was able to mate that close ratio M6 to a 3.42 rear gear.

Because of that I was significantly faster than cars with trannies from other years on the banking at California Speedway. We ran the ALMS course and you used about half of the banking on that 1.5 mile track and entered it from before the hot pits at about 100 mph. With only 230 rwhp and 3250 lbs (wet and with driver) the acceleration was at best..."deliberate" but I was much better off than the later 4th gens once they had to grab 5th (about the start/finish) line).

Don't recall the exact numbers but the 93 tranny had about 70% of the previous gears rpm every shift from 1st to 6th. The later M6s had about a 40-50% drop in rpm from 4th to 5th.




Perry

 

My speedometer stopped working after my T56 swap and some previous mods so instead of figuring out how to fix all that I put a Garmin Nuvi GPS that has it's own digital speedo right over the factory speedometer using the suction cup pivot mount on a large disc 2 way taped to the cluster.
Wired it in to turn on and off with the car.
I like it better than the factory speedo with the GPS 3D view