327_TPI_77_Maro

iTrader: (8)

I just regeared my 1989 trans am 305 TPI car to 3.73 gears. Still running 245/50/16 tires...the ideal, correct speedo gear combo now is 15T drive 44T driven. I put a 15T drive in the trans and i bought the closest you can get to a 44T driven vss style gear which is the 42T. Now the problem begins:

1990+ 4 pulse vss are available in 2 models, one for up to 39T, one for 40T on up driven gears. I first made the mistake of buying a 90+ 40T+ VSS then quickly realized its 4 pulse and I need 2 pulse...$70 wasted, next idea

I can't find that a 40T on up model 2 pulse VSS exists, does it? Or can I put the 42T driven gear on the 1989 stock vss (doubt it since i know even mechanical gears have 2 housings for driven gears depending on tooth count)

I see the Dakota digital conversion box and am currently reading the directions trying to understand if I can use this to send corrected signals to all of the dash, cruise, and ECM. Can I? Since I need the cruise, ECM, and speedo outputs to all be corrected, can I use the Dakota in between the VSS and the buffer? It does not look like the factory VSS uses one wire ground one wire signal though...is it a permantent magnet type output? Can the Dakota box then only convert the pulsed outputs after the buffer, and since I have separate outputs to the dash, cruise and ECM how would I correct all 3?

Help! I had no idea putting 3.73s in a pre 1990 tpi car was going to be such a problem getting the speed signal corrected. Thanks! Steven

vetteoz

iTrader: (13)

Not actually proven by me ,
but said trick is to rotate the VSS 180 degrees.
The difference between the two versions of a given type being the shaft offset to accommodate the different size driven gears
Have to mod the hold down bracket to suit

327_TPI_77_Maro

iTrader: (8)

Hey thanks for the idea! I have both the 39 and under and 40+ tooth vss so I will measure them and see if that makes sense, if so that would be far easier than some other options.

327_TPI_77_Maro

iTrader: (8)

Can anyone else comment on or confirm that to use a 40+ tooth gear on the 2 pulse original VSS that came with a 38 tooth gear in my 89 trans am that I can rotate the VSS 180 degrees? I searched on this board but could not find any other info on this. I found reference to the 40+ tooth 10456089 GM VSS but that is what I accidentally already purchased, and that is a 4 pulse sensor that you can not use with a 2 pulse car. I just don't want to do this wrong and tear up the 42 tooth vss driven gear, which was not easy to find. Thanks, STeven

vetteoz

iTrader: (13)

http://forums.corvetteforum.com/1554128332-post41.html

327_TPI_77_Maro

iTrader: (8)

I just measured the housings tonight using a fixture and a dial. Flipping the housing is NOT going to work. The 39 and down tooth housing has .075 eccentricity relative to the axis of the gear, and the 40+ tooth housing has .095". I checked both VSS and mechanical housings and came up with the same numbers. The high and low points for the 39 and down and 40+ housings are in the same place...flipping the housing is going to put the gear mesh way off. The guy in that link sounds like he has no idea what he is doing. Thank you for the link, at least I know where that came from (someone trying to shove a gear into a hole until it "fit". Yikes!)

John in RI

iTrader: (167)

I couldn't find a 40 tooth 'electric' gear in the 87 and down parts book. I did find a black 40 tooth in 82 & 83 ( PN 1362048 and sleeve PN25512339. It was used in cars with 2.93 gears.

327_TPI_77_Maro

iTrader: (8)

Those are mechanical gear and housing part #s, this is a 1989 electric VSS setup, totally different setup. I already have the gear, but it doesnt' look like there was a VSS for 40+ tooth gear in 89 is the problem, with the 2 pulse/rev VSS. 90+ had two vss, one for 39 and one for 40+ tooth gears, but those are 4 pulse/rev

John in RI

iTrader: (167)

Yup - no electric stuff in 82-83,.... I posted the part numbers so anyone hitting this thread in the future could use them.

The 89 electric is the same as my stock 84 system,... here's a pic of the tooth count for those that don't already know where to look:




Your situation is similar to T5 owners that have swapped to 3.73 gears and need an early electric sending unit,...... No one makes the proper tooth count T5 speedo gear !

Can't the digital dakota be used ?? I completely removed the stock VSS buffer in my 84 and installed the DD in it's place. I didn't need a signal to the ECM but I did hook it up to the cruise. ( but never installed the cruise throttle cable ! ) The factory speedo and an aftermarket digital speedo was hooked up the the converter and worked fine. (I had to use the DD converter because of a T56 swap......... ) I also used another DD box to convert the 4 pulse V8 distrib signal to a 3 pulse signal for use with a V6 tach. There's GOTTA' be a way that the DD box will work !

The only other option I can come up with in your case is to use a mech VSS with the proper speedo gears in the tranny and use an aftermerket converter to change the signal to electric.

327_TPI_77_Maro

iTrader: (8)

I already tried using an aftermarket VSS converter w/ mechanical gears. No dice. The aftermarket VSS converters use a reed switch, which is not compatible with the factory buffer, you get nada out the other end, it's expecting a magnetic VSS pickup.

Looks like I have to go w/ the Dakota digital. I can't believe putting 3.73s in this car caused this big of a problem, oh well thanks!