Hey CFI-EFI u have helped so many people on speedometer stuff.

Mine is a 85 vette, Auto, Changed Rear Gears from 2.59 to 3.54,
Front tires: 275/40/17 and Rear Tires: 315/35/17.

I already installed Electronic Ratio adapter bought from Zip products at the time when bought 3.54 gears on GP sale.
My mechanic installed this two wire spliced and connected to ECM wires going to tranny.

I also changed red drive gear to grey 15 tooth, 41 yellow driven and vss gear ratio which is 4 pulse but with no help. Reads 100-105 mph for 80-85 mph.

Do u want me to disable Electronic Ratio adapter? and just leave 15 tooth grey and 41 yellow color?

Also what is speedo caliberation ? is that any thing they hook up some scanner and do caliberation on speedo dash.

Thanks for ur help iam sure u will chime in as i have some free time tommorrow will take care of this problem.

Thanks once again helping me out. sami.

 

You seem to have quite a mess on your hands. It is my opinion that you go with the stock pieces/parts where ever possible. It uses proved engineered parts, and is usually cheaper. To me, the BEST way is with the grey, 15 tooth drive gear, the purple, 43 tooth driven gear and the 25007308 VSS. That older, 2 pulse per revolution VSS, is obsolete and no longer available. Since the 2.59 gears were not stock for your 1985, I have no idea if the VSS you removed was proper for these gears, or not. Can you tell me the number of teeth on the driven gear that came out of the original set up?

Since you bought the electronic ratio compensator, you didn't need to change out any of the stock pieces. Now you have a pair of speedo gears, for I don't know what ratio, spinning a VSS that neither your IP or ECM can interpret properly, funneled through a black box, that we have no idea what it is set to compensate from or to.

If you can go with the part numbers I've listed, it will the simplest and cheapest route. You can return the black box. Otherwise, I think you will need a 2 pulse per rotation VSS and calibrate the black box to convert from the ratio the speedo gears say they work for, to the 3.54's you are using.

RACE ON!!!

PS. Upon rereading this I see a couple of points that should be clarified. First, the purple 43 tooth driven gear is part number 25513050. Second, the 25007308, VSS listed above is the obsolete, 2 pulse per revolution, older style VSS that your car needs. Depending on the driven gear you removed, originally, you might have this VSS.

 

Thanks CFI for taking ur time and cleared those doubts i had,

The original gears came from my car was RED color probably 17 tooth and driven gear was green color.

Probably my rear gears were 2.73 (2.59 was just guestimate) and first without changing drive , driven and VSS i installed that black box than my mph was off little bit, changed jumper settings on Blk Box but still did not effect and again mph was off by 5 miles reading 30 mph instead of original 25 mph, than i bought these 15 grey, 42 green and VSS from transmissioncenter.com but this VSS (4 pulse) again dont know the diff in 4 and 2 pulse but clearly this(4 pulse) VSS is different than my original VSS (2 pulse).

Now i will disconnect Blk Box and install these 15 grey, 43 purple and most definetly i have to go with my original VSS i still saved that one in case if i could not find that rare VSS 2 pulse.

Sound like a deal to me and oh thanks a lot for letting me know the diff in 2 & 4 pulse stuff and thanks a lot again for those parts and thier corresponding part numbers. Damn i should not have listen to thier (zip products) blah blah blah........heck they r making money by selling thier blk box fake stuff for friggin 165 bucks, i will try sending back to them.

Thanks again CFI-EFI ur knowledge and help r outstanding.
sami.

 

Your red/green coloe conbination tells me your car was set up for 3.07 gears. The green driven gear is 42 teeth and your old, original, VSS for the green gear is just what you need to work with the purple gear. Too bad you blew all that dough on the black box when all you really needed was $30.00 or so, worth of gears.

RACE ON!!!

 

What can i say when i bought 3.54 gears as GP from zip products, almost i guess everyone bought this blk box so i thought it is required i wish i would have more knowledge about this, these things happen when u hotrod ur car mistakes mistakes ....... so on.

i just have to compromise my self as i saved 150 bucks in GP sale but spent 165 bucks in this fake blk box well u figure, anyway no regrets my mistake lack of info leads to these disasters.

Its thier (Zip) profession to sell products.

There's a good saying:
As long as fools r there, clevers never go hungry.

thanks a lot again to enlighten me of those 3.07 gears again wish i knew this never would have purchased 3.54 gears not much diff but instead went for 3.73's. sami.

 

CFI-EFI,
I too bought the 3.54 rear end during the Zip GP and the Abbott ratio adapter. I am going to install this weekend on my 91 with auto tran. They told me to make sure it is spliced in within 6" of the VSS but need to mount in a better location. I can splice in and run wires to mount in passenger console. I can run the wires in existing loom to get there but need to know where the best place would be to tap into ignition on hot wire. Also, do you think I should hook up and test first. I can run the wires up through the shifter console for test. Are these adapter really that bad? Thanks in advance for the input.

 

Me too me too. Jumps on the band wagon. I had a 3.07 original gears. Have not seen the color of my internal speedo gears on my automatic 700r4. I changed to a D44 with 3.55 gears. I bought an electronic gizmo to alter but have yet to get smart enough to figure it out. (wires, dip switches, etc.) Almost ready to take my car to tranny shop and ask them to Just do it with plastic gears.

 

I put a 3.73 in mine and used the Dakoda Digital electronic thingy.
I taped the VSS off the cluster. You set dip switches to calibrate for your ratio. Works great. Very easy.

 

Dave would u please explain more how u taped off the cluster.

what's the cluster means?.

I select those dip switches but still no effect reads 10 miles more than actual.

sami.

 

Sami,
scorp508 posted a reply to an electronic ratio adapter that was pretty good but I think the thread has been closed. It went something like this: 2.59 divided by 3.54 equals .731 so you need to knock the speedo down by .731. For the Abbott that means the dip switches would look like this 010001000111 Abbott told me I need to tap the VSS wires within 6" of the VSS on the tranny. I think dave is saying that he tapped power and ground off the intrument panel. I am trying to figure out which wire is in and which is out from VSS to feed to the Abbott adapter. Abbott also said be not to install box near anything that would create electronic interference like the radio.

 

Just to add. DO an advanced search using "Speedometer Gear Calibrator". Make sure to check archive and C4. There is a good post by SuperL98 that explains installation.

 

It's good that it is so easy, because it costs about 5 times the stock parts.


I don't know that there is anything wrong with the "adapter", but I can't imagine why anyone would fool with a finicky "black box" when Chevy has the parts you need available. For your 1991, automatic with 3.54 gears, use a grey, 15 tooth, drive gear, part number 8642620; a purple, 43 tooth, driven gear, part number 25513050, and a 10456091 VSS.


Or do it at home, yourself. The drive gear CAN be a bit of a project, however. You will need the same 8642620 drive gear and 25513050 driven gear as Rtremain (above), but because I know that you had a 3.07, I know that you can reuse your VSS. These gears shouldn't cost over $30.00. Return the $150.00++ black box.

RACE ON!!!

 

[QUOTE=CFI-EFI]It's good that it is so easy, because it costs about 5 times the stock parts.


I have a 4+3 trans and I put in a 3.73. You have to change both gears
to make it work and for a 3.73 the only gears I found were 2 times the cost of the box. Even if the gears were free I would still go with the
electronic box because on a 4+3 you have to pull the trans to get to one of the gears in. So there

 

I got power and ground from the radio. I installed an aftermarket radio
so it was easy to get to but all you need is switched power. The VSS signal goes to the Instrument Panel. I cut that wire to drive the Dakota Digital SGI-3 (I checked there web site and it's no longer available). I don't remember what color wire I used. I will have to look in my manual. Then you take the output of the SGI-3 and connect it to the other end of the wire you cut. To set the dip switches you need the ratio of real speed to speedometer speed.

55/65 =.846 So from the chart switch 1-8 on the SGI-3 is 11101001.

 

This might be your problem. I think the path of the VSS signal goes to the instrument panel then to the ECM. If your mech. spliced the signal after the IP the ECM will know the correct speed but the speedometer
will still be wrong. Can you scan you car and see what the ECM's speed is.

 

Thanks to everyone the problem solved:

Thanks CFI-EFI for letting me know my previous rear gear ratio was 3.07 and for the drive and driven gears (grey and purple).

Thanks to Dave: I recheck wiring today called Zip-products and justin gave excellent info on rewire and which wire goes to which one and solved the problem without changing gears.

I did this cuz my blk box (abott) already paid for and just had to play with wiring, and oh my tranny shift points changed too with new and correct speed.

Thanks a lot again to everyone especially CFI-EFI and dave.

 

Too bad you got stuck with that over priced black box, but at least it's done.

RACE ON!!!

 

I know iam stuck with blk box but my blk box already paid for what can i do. I would have take ur suggestion before i bought this blk box.

sami.

 

 

Do you still have that black box sami? I might need it. I'll do some research and start a thread first tho.