I'm seeing conflicting opinions on if a VSS is needed or not for a TBI Swap. Thought it would be interesting to see the results of a POLL.
CK5
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Vss poll!!!
- Thread starter Wicked Wolf Auto
- Start date
dave w
1/2 ton status
My experiece has shown me, the correct answer is both Yes / No. If you have a trail vehicle / only sometimes is used for daily driver use, then No the VSS is not needed. If you have a daily driver, that you'd be proud to let an elder family member use to visit the doctor, go do some shopping around town, then HELL YES you want the VSS!!!!!!!!!!!!!
Just depends on who is going to be driving, and the way the vehicle is going to be driven.
dave w
Last edited:
The correct answer is no! You do not need VSS with C3 type ECM> It is needed for C4 tpye PCM or the familar 16197427 ECM swap and it's also needed for TPI.
But my experiance has been stronger idle and better running with it.
I didn't vote cause I'm confused...
But my experiance has been stronger idle and better running with it.
I didn't vote cause I'm confused...
got both for ya.
87 cab swaped on my 79k30 with tbi 350.
speedo hooked up and all stock tbi wiring in place.
but speedo dosnt work. bad speedo head.
drives just fine last 4 years give or take . plowin snow/rail ridin/highway/intown and anything else i ask of it.
87 cab swaped on my 79k30 with tbi 350.
speedo hooked up and all stock tbi wiring in place.
but speedo dosnt work. bad speedo head.
drives just fine last 4 years give or take . plowin snow/rail ridin/highway/intown and anything else i ask of it.
MIKESMONZA
Registered Member
Vss
My 87 F.S. GMC "Jimmy 4X4",,Factory TBI
5.7, 700 R4 has the rear end 10 bolt
swapped from a stock 4:10 to a 3:42
It has the stock height tires 31''x10.25
and after market rims 15x10.xx ?
it has The VSS pick up is at the back of odometer cable driven!
and is driven by the output drive cable on the transfer case!
I will also replace the tranfercase speedometer output gears
4:10's to 3:42's to make the computer VSS Imput info
work for,
Rural Highway Driving and Ocasional dry, off road excursions,
For my application it works,,
where others might find it affect's:
Timing Advance , Power and FI Fuel Economy
I voted it positive!
My 87 F.S. GMC "Jimmy 4X4",,Factory TBI
5.7, 700 R4 has the rear end 10 bolt
swapped from a stock 4:10 to a 3:42
It has the stock height tires 31''x10.25
and after market rims 15x10.xx ?
it has The VSS pick up is at the back of odometer cable driven!
and is driven by the output drive cable on the transfer case!
I will also replace the tranfercase speedometer output gears
4:10's to 3:42's to make the computer VSS Imput info
work for,
Rural Highway Driving and Ocasional dry, off road excursions,
For my application it works,,
where others might find it affect's:
Timing Advance , Power and FI Fuel Economy
I voted it positive!
Doesn't that vehicle have a DRAC or VSSB? White box just off the ECM. You can make adjustments (soldering) in there to make your speedometer correct. I install a Dip Switch instead of all the little wires so you can dial in your speedo, or change again with next tire change.
The VSS for that reads the back of the speedo "magwheel" so if the cable is not broke and it turns then the VSS is still working even if the speeo is not. The speedo works on the other side of the magwheel and could still be dead and the VSS still work.
My vote is yes because i've had a FI swap where I forgot to hook up the VSS and there were idle issues when coming off of cruise and also stumble issues as well, once I plugged it in those problems went away. Also if you are running a later rig with cruise control the VSS is required in order for the cruise to work.
MIKESMONZA
Registered Member
EagleMark;
As I never noticed and have never seen a white box near the ECM on the TBI intake manifold bracket! (may be on other years later?)
Can you give me a drawing or picture of it?
> of a "VSSB" or a DRAC unit!
my hayes repair manual has general Pictures in black and white!
Will you please also give me the full skinny VSSB,,DRAC,,
!is there a acronim chart!
and yes a Adjustable "device"
would be really nice with pin switch"s!
And thanks for asking these questions!
As we all learn from the small to big things we might have missed!
Mike
As I never noticed and have never seen a white box near the ECM on the TBI intake manifold bracket! (may be on other years later?)
Can you give me a drawing or picture of it?
> of a "VSSB" or a DRAC unit!
my hayes repair manual has general Pictures in black and white!
Will you please also give me the full skinny VSSB,,DRAC,,
!is there a acronim chart!
and yes a Adjustable "device"
would be really nice with pin switch"s!
And thanks for asking these questions!
As we all learn from the small to big things we might have missed!
Mike
dave w
1/2 ton status
MIKESMONZA
Registered Member
Thanks that cleared that up !
,maybe it is not on this Model
87 F.S.GMC Jimmy TBI 5.7,,700 R4, 4X4,Tilt ,Cruise control,
Power everything,,
I had removed the dash bezel /instrument cluster,
and relaced it with another, (a milage trip odometer),,and made sure,,
that I swaped the original VSS green box back to the unit,,
I have 2 of the Hayes books some where in the Barn ,
,,,,,Have not found them yet, but will keep me busy looking!
,maybe it is not on this Model
87 F.S.GMC Jimmy TBI 5.7,,700 R4, 4X4,Tilt ,Cruise control,Power everything,,
I had removed the dash bezel /instrument cluster,
and relaced it with another, (a milage trip odometer),,and made sure,,
that I swaped the original VSS green box back to the unit,,
I have 2 of the Hayes books some where in the Barn ,
,,,,,Have not found them yet, but will keep me busy looking!
The DRAC system was used on 1990-later.
Finally found time to go hunt one down. Found one that had the little green box. I thought it would have been connected to the cluster but it was wired into the back of the speedo so it should work awesome in my existing cluster
It was GMs way of using same ECM on many trucks and cars and have same optical sensor to put in all speedometers and have same DRAC?VSSB for all that could be adjusted for gears and tires and end up with accutraate speedometers.
