Speedo signal from PCM

[JD1964]

Our LT1 swap into the 79 Malibu needs a solution for speedometer. We have the 4L60E with the swap so there is an electronic signal to and from the PCM that will be available. We dont want to hack up the original horizontal sweep speedo in the Malibu but since it normally works off a mechanical cable, I guess it wont be reading for us since the 4L60E has no cable drive. We were thinking of installing a stand alone GPS speedo and calling it a day.

I know we can buy expensive electronic cluster for the Malibu we're not loving that idea.

Do any of you have any other ideas or suggestions on speedo arrangement in a swap like this?

The GPS idea would probably be a 2" A pillar pod mount like this from AEM. > AEM GPS Speedometer (https://www.aemelectronics.com/products/gauges/digital-gauges/x-series/gpsspeed)

Thanks

[dave w]

Have you checked with JTR for the 4L60E cable driven speedometer options they offer? Rumor has it that some 700R4 tail housings that use cable speedometers will fit some 4L60E.

https://jagsthatrun.com/products/reluctor-ring-relocation-speedometer-clamp-for-4l60-e-4x4?_pos=1&_sid=b99275fa3&_ss=r

dave w

[JD1964]

Have you checked with JTR for the 4L60E cable driven speedometer options they offer? Rumor has it that some 700R4 tail housings that use cable speedometers will fit some 4L60E.

https://jagsthatrun.com/products/reluctor-ring-relocation-speedometer-clamp-for-4l60-e-4x4?_pos=1&_sid=b99275fa3&_ss=r

dave w

Won't I loose the electronic speed sensor from that location if I install a cable drive gear? I think that sensor is needed for transmission shifting control of the 4l60E via PCM. Is it not?

[dave w]

I recommend checking with JTR, they have a cake and icing solution!:thumbsup: (Both cable drive for the mechanical speedometer and the computer signal for shifting)

Not sure the solution is in the budget, but good cake and icing are rarely wallet friendly. :mad1:

dave w

[JD1964]

I recommend checking with JTR, they have a cake and icing solution!:thumbsup: (Both cable drive for the mechanical speedometer and the computer signal for shifting)

Not sure the solution is in the budget, but good cake and icing are rarely wallet friendly. :mad1:

dave w

Understood

[JD1964]

You talkin like this part is all I need?

https://jagsthatrun.com/collections/speed-sensors/products/copy-of-speedometer-gear-set-for-700-r4-or-4l60-e-with-4-pulse-integral-sleeve-it-just-drives-the-speedometer-cable

No wait...I bet I'd need a 700r4 tail housing and drive gear too.

Then there's this option, if I could splice into the VSS wiring for the signal without affecting its signal delivery to the PCM >

https://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=886/mode=prod/prd886.htm

[MQQN28]

15853
One of these or similar may be an option. Goes inline gives electronic pulse and mech cable attaches to end

[dave w]

I was thinking something like this for cake and icing: https://www.word-works.com/shiftworks/tailhousing.htm

The kit will convert your 1993-97 4L60E transmission to a factory mechanical speedometer while retaining a functional VSS capability. This is a simple 30 minute bolt-on installation.

The conversion kit includes the tail housing, new speedometer sleeve with new gear, new VSS sensor, new reluctor/drive gear bushing, and bolts.

$500

15855

Maybe DIY conversion would be less money?

dave w

[stew86MCSS396]

Chew on this but I can't seem to find any on Ebay or the wreckers...idk if it uses same reluctor/tone wheel though either.

http://www.montecarloss.com/community/ubbthreads.php?ubb=showflat&Number=1039065

Edit: Oops! I missed the part you said you have the long sweeping speedo! Move along, nothing to see here...



(http://www.montecarloss.com/community/ubbthreads.php?ubb=showflat&Number=1039065)

[tayto]

a standard 700r4 tailshaft will bolt providing the 4l60e has is pre 98. you can then swap a 700r4 output shaft or carefully measure and drill the hole for the speedo clip. then you can run a speedo cable. either run an inline vss or drill/tap or weld on a magnetic sensor and press on a 40 tooth reluctor behind in front of the speedo drive gear. the shift works is a nice piece but expensive. if you don't have the skill set to mod one probably worth it.

not my "thing" but pretty sure Dakota makes a digital dash for that era a-body....

[B52Bombardier1]

A 79 Malibu is not an "A-Body". That would be a 68-72 Chevelle, El Camino, Monte Carlo, etc. But yes, a Dakota Digital HDX cluster is my thing and it works well on my 70 El Camino using the VSS / speedometer signal from the PCM. And it is very accurate once calibrated along a precisely measured one mile length of road.

Rick

[tayto]

I was under the impression 78-80 was considered an a-body then in 81 they renamed to g-body and a-body turned into FWD.

[JD1964]

g-body was from 78-87

[stew86MCSS396]

https://gbodynation.com/g-body-not-g-body/ :rolleye:

[lionelhutz]

I'd say you're looking for one or more of these products. Top row of the search mostly.

https://jagsthatrun.com/search?type=product&q=4L60

I personally wouldn't run the PCM from an inline sensor. Any instability of the sensor signal will mess with the transmission operation. The sensor that plugs into the tailshaft and gives both is 4000 pules per mile. The 40 tooth reluctor ring is typically something like 50,000 or more pulses per mile. I don't know if the lower pulse signal would mess with the transmission operation or not.

Dakota Digital has a dash for $800. Their dashes give some really nice features and work well. I tried to figure out what you're trying to do for a 65 Impala, but finally just did the DD dash. They didn't have a dash for the car at the time so I modified the dash insert and made a universal cluster work . It ended up being a much, much cleaner installation. The advantages were well worth the extra cost vs trying to add both a cable and pulse output to the transmission.

I couldn't see the point at all of using one of those $500 cable driver boxes compared to what the DD dash at $800 gives. For me, that was not even worth a second though.

[tayto]

https://gbodynation.com/g-body-not-g-body/ :rolleye:
all the same thing, but not wrong to refer to them as "A-bodies". I recall having this debate in high school hah

[ScottP]

This is the solution I used in my '70 Bonneville:

https://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=886/mode=prod/prd886.htm

It accepts the VSS output from my 12200411 PCM and drives the stock mechanical speedo perfectly.
The box is easy to mount and hide behind the dash.

-Scott

[JD1964]

Allow me to revive this thread about speedometer options for the 94 LT1 in the 79 Malibu.

Does the 1994 Z28 PCM speed signal output deliver a square wave signal? If so i think this 2 1/16” gauge might be a solution for a low budget. Id mount it in a pillar pod. Do you think it will work? The install instructions are also available at the linked page.

https://www.glowshiftdirect.com/10-color-digital-speedometer-gauge/

[tayto]

the input to the PCM is analog (40 tooth reluctor wheel), the output is either 2000 ppm or 4000 ppm squarewave. I would just bite the bullet and buy the speedhut or Dakota digital mechanical converter and use the original speedometer.

why don't you just use a cellphone or gps for speed?

[JD1964]

the input to the PCM is analog (40 tooth reluctor wheel), the output is either 2000 ppm or 4000 ppm squarewave. I would just bite the bullet and buy the speedhut or Dakota digital mechanical converter and use the original speedometer.

why don't you just use a cellphone or gps for speed?

I dont like the lag time of gps sourced speedometer.

You are right however. I should bite the bullet and get the Dakota speedo driver. The factory speedometer is in good order and it would be nice to use it. Ill probably eventually pry $350 out of my wallet and do it that way.

[tayto]

I wish there was a cheaper alternative. there is thE diy route but i just don't have the time. hooking up an existing speedometer motor with gm stuff is actually fairly easy. However the deal breaker for me is a non-functional odometer. you need a unit that screws to the existing speedometer head. I have seen companies that offer to convert existing gauges, but they stick a digital odometer in place of the old mechanical one. it works but not for me.

I would check out the Speedbox from Speedhut, i have heard it is quieter than the Dakota unit and i think can be mounted under the hood. They are actually on sale right now, I might pull the trigger myself as I will need one for my project soon.

speedhut.com/categories/speedbox.html

[lionelhutz]

PCM output is 4000ppm assuming the PCM is calibrated. It's a transistor driver to ground, so it needs a pull-up resistor to work.