Anyone with some technical data of the older style cruise on our trucks

[Russell]

Ok, as some of you guys may know, I'm installing a TPI setup in my truck. What I'm trying to figure out is how I am gonna rig up the VSS (Vehicle Speed Sensor) Now, I have that cruise setup with the speedo cable going into a box on my driver's side fender, then out and up to my speedo, does anyone know if I can possibly use that VSS to supply my ECM with the vehicle speed info it needs rather than trying to mess around with my TH400?

What I need to know is what kind of frequency it puts out, and which wires have that information in them...

[Grim Reaper]

Not sure the pulse rate is correct. I use to know what the pulse rate was but slips my mond right now. It's worth a try though. Just hook a VOM to the wires till you can read a pulse. Cross check the voltage.

Now if it were me what I would do is go to the junk yard and find a Sub with a TH400 built 87-89 maybe 90. The VSS is in the back of the speedometer. Grab the fuse box, wring and cluster and it should all be a bolt on 78 up with blade fuses in and get you the correct VSS...nevermind that might be too much trouble. You have to change the colum if you were trying to retain the Crusie. I bet you could wire in the cluster though to get the VSS.

Option #2 is there is a through drive VSS that will let you hook a VSS into the standard Speedo drive and it will still let you drive a standard Speedo. I think that's available from Jegs and Summit.

If you go to www.ck5.com and hit the 73-91 Forum I have a links post at the top. A bunch of FI sites listed there. Go to the F body sites they have some good info on VSS options.

[Grim Reaper]

Rattle in my brain says your looking for 2 pulses per second at 60mph.

[Russell]

Originally Posted by Grim Reaper

Rattle in my brain says your looking for 2 pulses per second at 60mph.

That would be the one or 2000 pulses a mile.

This cruise module won't work for that, it'd only put out 1000 pulses a mile. I gotta figure out what kind of a car and or truck I could get the 2 pulse setup off of, or if I should just go and buy one...

[Jonboy]

Check out the Jaguars that run site, I think it is www.jagsthatrun.com . There is a whole chapter in his book relating to the VSS, and most of that is on their website as well.

[RockHQ]

I don't have GM shop manuals at home, but at work we've got most of them for ~1983-2004 GM passenger cars/light duty trucks, time permitting i can look for any information you'll need. Also a few different EPCs if you need GM part numbers.

Although i can't remember when the old body style light duty trucks got electronic (not cable driven) speedometers, i think you should be looking at a 89-91 2500 Suburban, or a 2500/3500 pickup. As long as it's a th400 truck, with no speedo drive cable. I do know that my blazer has an electronic speedo.

[Russell]

Can you check to see what the pulse rate for one of those VSS modules on the back of the later speedometers is?

[Captkaos]

I thought the VSS on the Cruise for the pickups had a 2000 pulse VSS. I didn't know GM used a 1000 pulse, are you sure about this? Or just guessing. I am pretty sure the carb computer controlled vehicles used a 2000 pulse (square-wave) setup

I have a TPI I plan to put on the Jimmy, also.

[Russell]

The thing I was looking at was the cruise module thing sitting on my driver's side inner fender, I took it apart and saw that the way it would work would only produce 1 pulse per rotation of the speedo cable.

If the VSS for the pickups that is attached to the back of the speedo is a 2 pulse setup, then we can use that speedo for the TPI. I dunno if it needs a special module or if it can be directly attached to the ecm though...

[RockHQ]

R/V/P series light duty trucks used a DRAC, or digital ratio adapter controller to convert the analog signal suplied by the VSS (which is really a permanent magnet signal generator) located in the transmission output shaft to a digital signal, which is then fed to the speedo. Different DRACs are (were) available to compensate for different rear end gearing, tire size changes etc, so that the speedometer remained accurate. I think i can get the part numbers for the different DRACs.

[Grim Reaper]

Originally Posted by RockHQ

R/V/P series light duty trucks used a DRAC, or digital ratio adapter controller to convert the analog signal suplied by the VSS (which is really a permanent magnet signal generator) located in the transmission output shaft to a digital signal, which is then fed to the speedo. Different DRACs are (were) available to compensate for different rear end gearing, tire size changes etc, so that the speedometer remained accurate. I think i can get the part numbers for the different DRACs.

I don't think the 87-89 454 Subs use the drac. I have a complete 454 TH400 89 FI system with all the sensors on the shelf including the VSS without the rest of the cluster. It's the same VSS used for the cruise. In those years the FI for the 454 was just about a bolt on to a 86. The Throttle body will bolt onto a standard 4bb spreadbor intake.
On the VSS on those vehciels It's a optical pickup so it should work fine. You have to get the whole cluster though because the VSS on that style mounts to the back of the cluster over a hole that has a spinning disc on the speedometer that has the trigger. You might be able to swap the speedo over and retain the rest of the older gages. Not sure.

[Russell]

Hmm... I like the sounds of that... How much would a DRAC cost?

[RockHQ]

Well my friend, that's something i would not have any idea of. I do know that were i to buy one, with employee discounts it'd still be twice the retail price in the US

[Captkaos]

Grim is correct. It uses optical VSS on the speedo. I don't think Drac was used on the "old style" trucks until ABS came into play.

I believe you can keep the current cluster and just pull the Speedo. You would just need to tap into the signal on the VSS wires to get it to the ECM. I have one at home that has the VSS I will pull it apart and see if you need the cluster or just the speedo.

[RockHQ]

Grim, it seems what you have is the "early version", which was replaced by a transmission mounted permanent magnet generator VSS. 1989 to 1991 are troublesome years, since two different model lines C/K vs. R/V were produced with two different chassis electrical configurations on both model lines. I do know, and i can quote a GM shop manual, that 1990 the speedometer was not cable driven nor does it have any sort of optical VSS provisions. I do know that the same configuration was used late 1989 (have worked on trucks of that MY) to 1991 (own a truck of MY 1990, or VIN L). I did not have time to really look into it today (too many customers+a 1990 cadillac fleetwood with electrical problems like that's anything new ) but the 1990 R/V/P shop manual i was looking at made no mention of a cable driven optical VSS. Sometime during 1991, the 4L80E became the replacement for TH400, however i have not verified if it ever was available to the old body style trucks (73-91).

To get back on topic, Russell if you want to keep your original gauge cluster then an aftermarket VSS mounted to the transmission or whereever could be the best choice. Or perhaps you could use the output signal of your current VSS. It's not out of the question to make your own VSS, either. Most VSS sensors produce alternating current (AC), which can be verified with a voltmeter set to the AC mode with a 200 volt range. You only need the pick-up and a slotted wheel with the correct amount of slots in it.

Good luck,

-Axle


[edit]

Capt, GM magnetic VSS generators predate ABS.

[Captkaos]

Originally Posted by RockHQ

[edit]
Capt, GM magnetic VSS generators predate ABS.

I was speaking of the 87-91 trucks only and mainly 1/2T. I believe the switchover to the tranny mounted VSS started in 1990 on the 1973-1991 bodystyle. These models were not offered with the 4L80E as far as 1/2T goes. On the 91-later 3/4T trucks with the new bodystyle it was an option though. 1/2T's in the old bodystyle only had the 700R4/4L60. The dual lines created alot of confusion here, so.....

As for using an aftermarket VSS, Dakota Digital has one here:
http://www.dakotadigital.com/Detail....rtNumber=SGI-5
If interested in this let me know and I will see if I can get a better price.

AND www.jagsthatrun.com have a few here:
http://www.jagsthatrun.com/Pages/Spe...eedometer.html

[Grim Reaper]

Originally Posted by RockHQ

Grim, it seems what you have is the "early version", which was replaced by a transmission mounted permanent magnet generator VSS. 1989 to 1991 are troublesome years, since two different model lines C/K vs. R/V were produced with two different chassis electrical configurations on both model lines. I do know, and i can quote a GM shop manual, that 1990 the speedometer was not cable driven nor does it have any sort of optical VSS provisions. I do know that the same configuration was used late 1989 (have worked on trucks of that MY) to 1991 (own a truck of MY 1990, or VIN L). I did not have time to really look into it today (too many customers+a 1990 cadillac fleetwood with electrical problems like that's anything new ) but the 1990 R/V/P shop manual i was looking at made no mention of a cable driven optical VSS. Sometime during 1991, the 4L80E became the replacement for TH400, however i have not verified if it ever was available to the old body style trucks (73-91).

To get back on topic, Russell if you want to keep your original gauge cluster then an aftermarket VSS mounted to the transmission or whereever could be the best choice. Or perhaps you could use the output signal of your current VSS. It's not out of the question to make your own VSS, either. Most VSS sensors produce alternating current (AC), which can be verified with a voltmeter set to the AC mode with a 200 volt range. You only need the pick-up and a slotted wheel with the correct amount of slots in it.

Good luck,

-Axle


[edit]

Capt, GM magnetic VSS generators predate ABS.

4L80 was avialble in the R/V series 91 Subs and Maybe the 90. In 1990 on the 454 powered burbs there was some changes to the FI and I think that's the year the electronic speedo showed up as well. It would make sinse that change came with the 4l80. The intake was changed from the spreadbore to the style that acepted the throttle body with out the adaptor to the spreadbore.

It was 88 When the confusion started with the C/K vs R/V. Just nuts. Then in 90 and 91 they adoped the new trannies and cases EXCEPT the new body trucks has a driverside drop. So you bust a GM version NP241 with a passengerside drop your hosed! That case was like 1-1.5 years only. Right now people are having problems with getting the rubber mounts for those and nobody makes a aftermarket Poly for it.

Steve at www.ck5.com had a hell of a time with getting his stuff to all work when he started having problems with the 241. He went to a doubler and had to have a NP205 tail housing and tone ring custome made/machined to drive the VSS for his FI and so his speedometer would work.

[Russell]

Hey, I emailed a couple of speedo shops, and they all agree that the green box is a 2 pulse setup, which means that we could probally just put a later speedo into our dash bezels and have our VSS right there in a factory position

Just need to find out if the signal needs to be amplified or if we can just hook the VSS straight to the ECM...

[1972C10]

I installed cruise in my 85 that never had it I used the speedo Vss it hooked up with three wires one ground hot IGN Hot and the output V.S.S i dont know how many pulses but i wondered if i could run FI off it.

91 blazers have electric speedos and you can get a sender off a 88up th375 or th400 I may have one if i strip a truck i have I wont be needing the elec speedo.

[Russell]

Wicked, that sounds perfect... If the VSS box has a hot, ground and output wire, it can be directly connected to the ECM -- What a perfect solution...

[1972C10]

Yeah i just got the vss and the harness that hooks to it with about 12" leads i think the wires were yellow red blk yellow was sensor blk ground and red ign hot
I soldered mine up with some factory ends that plug into the fuse panel

I figure since your doing it might as well do it right.

[red450ih]

Not trying to steal a post, but you fellas sound knowledgeable on the cruise control in these trucks. Does anyone know of a website or a book that I could get to diagnose and repair a cruise unit in an '89 V1500 Suburban with 6.2? The PO said the column switch was the problem. Don't know where to start with the diagnoses.

Also, I want to install a factory cruise set up on my '83 K20 with 6.2 from an '84 Suburban with a 6.2. From what I have read the '83s had two different kinds of cruise units.

Thanks,
Keith

[Jonboy]

Since you have an 80 model truck with the newer style script on it, why not run the 87-up speedo in your housing, or get the whole cluster. IIRC, you should be able to get a trip odometer after 88.

[1972C10]

The switch is pretty simple 12 volt ign switchec input when its On 12 v out and whe you tap accel 12 volt momentary and when you tap coast 12 volt momentary i dont recall the color code but I may have a diagram out in the shop if so ill post what color wire does what its only four wires on the switch

[Russell]

The only reason why I want to run the old style housing is that I'll have a tach dash with the blue outline -- So I'll look funny to put an 85 mph / 140 km/h red outlined gauge in with it...