Using an electronic speedo with TBI and 700R4?

[clinebarger]

Originally Posted by mcbassin

Any ideas of what wires beside ground, cluster and vss signal that must be connected?

Here is the 91 Suburban diagram from my good friend Cableguy:

C11 of the DRAC will go to the A10 terminal on the 24 pin connector of the ECM (curcuit #437, wire color-brown), This is needed for TCC, EGR & IAC functions.

C9 of the DRAC will need to be hooked to a ignition hot (curcuit #50, wire color-brown)

[ChevyTech]

Great photo of the DRAC jumpers mcbassin.

This looks to me to be a DRAC from a vehicle with a 3.42 axle ratio and P225/75R15 tires.

A 3.42 axle ratio would have an RPO code of GU6

If you find out what axle ratio the truck has, or get me the PRO code from the truck, I can tell you which jumpers to change.

[mcbassin]

Originally Posted by ChevyTech

Great photo of the DRAC jumpers mcbassin.

This looks to me to be a DRAC from a vehicle with a 3.42 axle ratio and P225/75R15 tires.

A 3.42 axle ratio would have an RPO code of GU6

If you find out what axle ratio the truck has, or get me the PRO code from the truck, I can tell you which jumpers to change.

Is there any way to tell from the vin# what axle gears it has?
Vin: 1GCDC14HXGF432259

[raycow]

Originally Posted by mcbassin

Is there any way to tell from the vin# what axle gears it has?
Vin: 1GCDC14HXGF432259

Finding out what axle ratio you have is the easiest part of the whole job.

Put matching marks on the pinion yoke and differential housing. Jack one rear wheel off the ground, put the transmission in neutral, and the parking brake off. Turn the wheel exactly TWO revolutions and count how many times the driveshaft turns, estimating any fractional turn as closely as possible. That number is your axle ratio.

If the wheel is difficult or impossible to turn, you may have posi. In that case, jack both rear wheels off the ground and turn either of them only ONE revolution. Count the driveshaft turns the same way as for an open rear.

Ray

[mcbassin]

Originally Posted by raycow

Finding out what axle ratio you have is the easiest part of the whole job.

Put matching marks on the pinion yoke and differential housing. Jack one rear wheel off the ground, put the transmission in neutral, and the parking brake off. Turn the wheel exactly TWO revolutions and count how many times the driveshaft turns, estimating any fractional turn as closely as possible. That number is your axle ratio.

If the wheel is difficult or impossible to turn, you may have posi. In that case, jack both rear wheels off the ground and turn either of them only ONE revolution. Count the driveshaft turns the same way as for an open rear.

Ray

I assume I have to turn it 2 turns because it is a non-posi diff?

[cableguy0]

Just pop the diff cover off and count the teeth. The fluid likely needs changed anyhow.

[mcbassin]

Originally Posted by cableguy0

Just pop the diff cover off and count the teeth. The fluid likely needs changed anyhow.

Good call! who knows how long its been since it's been changed?

[cableguy0]

Its most likely the fluid it came from the factory with 25 years ago.

[mcbassin]

Update:
I finally got a little time to install the DRAC module. Still no working speedo. I really don't understand what's going on. I'm pretty certain I wired it like the 91 suburb diagram. I'm wondering if this setup may not be compatable with the 700r4 out of the Buick roadmaster? The wire colors are different and the diagram doesn't show a DRAC module or maybe I don't have the diagram that shows it? Take a look at the attached diagram and see what you think.

Cableguy, can you look at the 1992 Buick diagram and see if it shows a DRAC module? I sure appreciate all the help! this is very frustrating!

[cableguy0]

The setup from the roadmaster is completely different. The speed sensor signal goes into a vss and from there feeds into ecm,cruise,cluster,audio alarm etc etc etc.You might end up having to go yank a speed sensor out of a suburban to get the proper reading. Im assuming the buick had digital dash and all? The wiring is completely different than a truck would be. I would try grabbing the speed sensor out of a 700r4 from a truck or suburban.

[mcbassin]

Originally Posted by cableguy0

The setup from the roadmaster is completely different. The speed sensor signal goes into a vss and from there feeds into ecm,cruise,cluster,audio alarm etc etc etc.You might end up having to go yank a speed sensor out of a suburban to get the proper reading. Im assuming the buick had digital dash and all? The wiring is completely different than a truck would be. I would try grabbing the speed sensor out of a 700r4 from a truck or suburban.

Thanks! that's what I was afraid of. I guess I will trek out to the pull a part again this weekend. I wonder if the burb has a two wire setup on the vss?

[cableguy0]

Its looks like they are both 2 wire off the trans but the buick hooks up to like 6 extra things and uses a completely different style module under the dash. The speed sensor signal goes to half the damn car in the buick.

[mcbassin]

I hooked everything up just like the diagrams and the speedo doesn't work. I did notice for the first time yesterday that the needle moves just a little when the key is turned over. Also, since my son has been driving it the trip odometer has accumulated 15 miles. So, is it safe to assume, I have a bad speedo or wrong signal from the DRAC? any help?