budofbama31313

My car is a 91 Z28 with the L98 that I have bored and stroked out to a 383 and kept the TPI on it. Replaced the 700R4 with a T56 and installed a dash from a 97 Z28. Okay my problem is that my speedometer is at 150mph by the time I'm doing 20mph and the tach is at 2500 at idle and 3500+ while cruising. My question is; do I still need the dakota digital box to fix this problem or have I not hooked somthing up like a stray ground. I've searched and read and read some more but yet to find somebody with the same setup as mine, but that is very hard for me to believe. I've used a 97 V-6 cluster from a Camaro and a 95 V-8 cluster from a firebird and had the same out come. Somebody please help me out. Thanks in advance.

budofbama31313

The amount of responses and type of help that I see people get on this board I thought I'd get alittle but guess not. anyway, I spent all day digging through the wiring under the dash and looking for lose or unattached grounds to come up empty handed. Any help here would be helpful, but won't be working on it till January.

87transGTA

id love to help ya dude but im confused about it also i was thinkin grounds to but since u came up empty handed idk what to tell you but good luck and if you need any wiring diagrams id be glad to send you them

Toyota h8r

only thing i can come up with is that the speed reading sensor (VSS) is wrong unit for dash....or wiring issue. you try a different VSS unit?


and for the tach thing.....97 dash = lt1....lt1's used optical sensors to obtain the rpm counts on the motor. Where as you have a distributor and its giving the dash a different reading and the tach isnt showing a correct reading.

budofbama31313

After Christmas I may hit you up, thanks man

Yeah I thought about the VSS, but it is the correct kind for my cluster because the trans came from a 95 and the cluster from a 97. And being that a t56 isn't easy to find in thr jy I can only hope it is good.
I haven't thought about how the LT1's sent the signal to the cluster, I may have been chasing my tail on that one.

Hey thanks guys for ur help.

Toyota h8r

all i can do is try

about the vss....maybe the wiring is different and the vss is right?


i wonder somewhere in the conversion a wire got crossed? that or used wrong wire?

i assume that its a wiring issue.....try using the old vss if its the same design?

mcgarnicle

iTrader: (14)

Is your VSS signal going through the ECM first or straight to the speedo? As your original setup would have been that way, your computer is still expecting a 2000-4000ppm where as the T56 sends somewhere in the area of 40,000ppm. If that is the case then you would need a SGI-5c box and calibrate your speedo with that.

As for the tach reading off I'm not sure I'm understanding what your saying. At idle it is at 2500 and cruising at 3500+. Do you mean it is off by a percentage that through acceleration the reading is more and more off? Or just sits around 3500 while driving around?

budofbama31313

The VSS still sends the signal through the same route as before. Only difference is now it comes from a T-56 instead of a 700R4 and goes through the wiring harness to a 97Z28 cluster instead of a 91Z28 cluster.
As for the tach while the car is idling the tach is bouncing from 2000rpm to 2500rpm, while I'm going down the road it is anywhere from 3500rpm to pegged out redline. Very unperdicable.

mcgarnicle

iTrader: (14)

Well I think we found out why your speedo reads off by so much. An SGI5c box will correct this but you will still need to manually adjust it usually done by matching someone elses speed. I'm not sure but since your car originally used an electric signal if you could just switch out the vss from say like a 5 speed car? IDK I never looked around for that answer since my car was cable driven, something to think about though.

as for your tach I have no idea, it's getting a signal and the signal seems to increase while in motion (or revving the engine?). This is a sticky in the body section (for whatever reason) but it is all the wiring for a 93 dash into an 85 tpi car.

https://www.thirdgen.org/forums/body...ring-good.html

Probably not exact to your situation but does have a pinout on his 4th gen dash that you can reference against your wiring.
Hope this helps and good luck.

mcgarnicle

iTrader: (14)

did you ever get this sorted out?

budofbama31313

No sadly not. I just got back in town lastnight and will be looking into it this week. Will be borrowing a buddy's ecm to see if it corrects any of the problem. I'll post my results.

JTNKTZ

iTrader: (10)

Correct me if I am wrong but doesn't the VSS run off ratios? Maybe you should look into that. Maybe you have the wrong speed drive gear? That's all I can think of.

mcgarnicle

iTrader: (14)

The speedo drive gears don't really have anything to do with his speedo being off by how much it is. The problem isn't that the ecm is bad or wrong. The problem is is that your computer sends it's readings from the vss to the speedo, when it is getting a huge reading, like the normal reading from a t56 vss, it sends that to the speedo and you have happen what is happening, doing 5 mph and getting a reading of around 120mph.

The solution is the SGI-5c box. Or you can drop in a LT1 and run it's computer and the speedo will run correctly.

budofbama31313

I think this is my solution also (SGI-5C) but just want to rule out the ecm since I'm having some other issues.
As for the other, well the 383 may have 1000 miles on it, I haven't enjoyed the 383 much yet, and MONEY. As tempting as this may be, kinda like putting a tornique at the shoulder for a paper cut on the finger. Made me laugh none the less.

BrOdBaNd

iTrader: (8)

Well.. With my 4th gen dash and 97 cluster with my 700r4 and 350, my tach reads off also... I read about this and from what I have heard the tach signal goes through the LT1 computer, so unless you get an LT1 computer it will never read right... Someone please make sure that this is correct information? What about running straight from the coil?

monte-ss

Any luck so far? Im looking at doing pretty much the same thing have an 89 TPI and planning to do a T56 conversion with a mid 90's cluster Supposedly cheaper than paying the 550 to have the tail shaft modded to accept a mechanical speedo cable.

budofbama31313

I thought this thread died, so that is why I haven't checked it. But here is where I stand. I swapped out my ECM from my buddy's car and same problem and with my ecm in his car it run and idled fine (so ecm checked out). Ordered the SGI-5C box on Feb 17, recieved Feb 26, installed Feb 28. Between the 17th and the 26 is where "MY" luck kicked in. On Feb 23 I idled off from a red light coming home and it wouldn't shift into 2nd, 3rd but I was able to musle it into 4th and limp it home. Yesterday I drop the tranny to find two of the four clutch springs where dislodged from their proper location and just rolling around in the clutch kit. I called the parts house I got it from to find out that it was still under warranty. Thought I was dreaming at first. They got the new kit in today and as soon as he pulled it out I thought was for a 5speed because it had five sets of springs instead of four. We rechecked the part #, # of splines, diameter, bolt holes and even the aglinement tool. All things matched except for the extra spring set. The guy told me the company must have corrected a flaw in the way they made them. I will be reinstalling the tranny this weekend and will post my results. It seems to never end.

budofbama31313

Finally oh finally!!! Rehung my trans and back in motion now. After driving up and down the road and searching high and low on here I figured out that I couldn't use the orange w/black strip wire and black wire that used to hook up to the auto shifter for the power and ground source for the SGI-5 box. I still don't understand why, the orange one checked out to have juice with the key on and the black one ohm'ed out to a known ground. After wiring it up to a constant power and ground the speedo works properly.

As for the tach, well I'll just live with it for now. Got to focus on moving soon.

monte-ss

Glad you got it all set up and running, so to make sure your using the stock VSS on the T56, the dakota SGI-5 and the 97 gauges? Enjoy it hopefully I will be in the near future!

budofbama31313

Yes the trans is all stock including the VSS hooked up to a SGI-5C box run through the wiring harness then on to the 97 cluster. It's good to finally see the speedo needle work like it's supposed to and not peg out at 150mph while doing 15mph.

mcgarnicle

iTrader: (14)

That's good you got it straightened out. As for your tach I'm sure that it isn't anything too serious, enough people on this board have done that dash swap and seem to have everything working. I would look for other members who have done it and ask if they have any problems with their tach and if not ask how they wired it up.