4l80e Speedometer Options

[Doppleganger]

I have looked and any similar posts either were never answered or (on other sites) the pics or associated links were hosted on Photofcket or the companies sites are gone.

My truck is 4wd. The 4l80e I have is from a 2WD. Best way to go from what I've found. Output shafts and the adapters for 4wd are cheap and the 2wd's are guaranteed to have the VSS ring in them.

My question involves the speedometer. I have heard of guys using the single VSS signal for both, but say its not recommended or they have issues. Dunno. I fully intend on going aftermarket with the gauges but was hoping not to HAVE to do that just yet. Trying to pace my trip to bankruptcy. lol

Someone on another board had a link to a company that made an adapter to use the cable, but that site (and the company?) is gone....not surprising - the reviews were terrible.

What did you fellas use or do here? I'm going to use the OE PCM to drive the 4l80e.

TIA.

 

[Matt69olds]

If your going aftermarket gauges get a speedo that’s compatible with the VSS of the 4l80. Another option is a custom extension housing that accepts the old 400 speedo gears.

 

[Matt69olds]

I just noticed your truck is a 4wd, you won’t need the speedo in the trans. The speedo will need to be driven from the transfer case. That’s outside my area of expertise, I have no idea what options are available for transfercases

 

[Doppleganger]

I dont think the speedo cable goes to my 208C - ?! The 4wd 4l80's are in the transfer case, but have the boss for the sensor in the trans - which is added if swapped into an older truck. The 2wd's already have them, so no need to spend the $ to get it. Same difference (what I am told 10x over by everyone that builds transmissions).

What I have also read is that if I use the factory PCM, it will have a signal out to an electronic speedo that runs it too. Again.....dunno. And who would I get to program or make the harness for the PCM?

My Plan B is to get a GPS speedo that wouldn't need a VSS signal. Would like to have my cruise back but no idea how that would work either. Further I get into this the bigger the mess it is.

 

[RoryH19]

My k5 had the mechanical speedo in the NP208c. When I swapped I went with the NP241c. A stronger T-case and it has the vss.

If I recall one wire for ground the other for signal.
The cable/wire connects to the PCM then from the PCM to the gauge cluster, one wire.
This of course controls the shifts of the trans and tells the speed.
Mine is always within 1 MPH compared to my phone's GPS if not the same.

I recall Dakota digital makes an adaptor to convert from mechanical to vss.
4k pulse

I also have cruise control.
Since mine is DBW TB, I was able to use the stock 4 wire cruise control lever (83+).

 

[TubeTruck]

The problem with running off the VSS ring in the transmission is when you put it in 4wd low your transmission doesn't shift right. Depending on your transfer case there are several options. Like @RoryH19 said, you can use the NP241c and run off the VSS in that, or if you have an NP205 ORD makes a "kit" to put the VSS in place of the speedo gear. You have to mail them the tail housing and they machine it and send you the new ring, sensor, and wiring.


From another site but seems to be very accurate:
Early 4l80's have the two Speed sensors in the transmission case. They are ISS & OSS. The one on the transfer case is for your speedo, it is VSS. Later 4L80's used only an ISS & used the VSS in the transfer case for the output speed sensor.

To use the 4L80's output speed sensor for a VSS would require some DRAC modification to run a speedometer. Also your speedo would not be correct in low range. You would also get a speedometer reading with the t-case in neutral & the transmission in gear.


What year is your 4L80E? What t-case are you using?


https://www.offroaddesign.com/catalog/product/view/id/488/category/515/

 

[Doppleganger]

At the moment, all I have is the 208C that came with the truck (85 K20). The trans is a 2000 - from a van so a bell housing actually for the 5.7.

I just have no idea what to collect (as its back breaking to try and pay it all forward at once) for when the motor comes back in the Spring.

And NO ONE knows anything about it around here.

 

[RoryH19]

The problem with running off the VSS ring in the transmission is when you put it in 4wd low your transmission doesn't shift right. Depending on your transfer case there are several options. Like @RoryH19 said, you can use the NP241c and run off the VSS in that, or if you have an NP205 ORD makes a "kit" to put the VSS in place of the speedo gear. You have to mail them the tail housing and they machine it and send you the new ring, sensor, and wiring.


From another site but seems to be very accurate:
Early 4l80's have the two Speed sensors in the transmission case. They are ISS & OSS. The one on the transfer case is for your speedo, it is VSS. Later 4L80's used only an ISS & used the VSS in the transfer case for the output speed sensor.

To use the 4L80's output speed sensor for a VSS would require some DRAC modification to run a speedometer. Also your speedo would not be correct in low range. You would also get a speedometer reading with the t-case in neutral & the transmission in gear.


What year is your 4L80E? What t-case are you using?


https://www.offroaddesign.com/catalog/product/view/id/488/category/515/

Good point on the 4 low of the T-case. You reminded me there is an additional wire that needs to be set to ground when in 4 low. Can be done by micro switch in the lever or just a simple toggle.

 

[TubeTruck]

Forgot to add that you can run the transmission off the VSS and use a gps speedo. That way you can change tire size, gear ratio, whatever you want and your speedo will always be correct.

 

[JoeR Jr]

For driving the speedometer there are a couple of choices.
This is one: https://www.jegs.com/i/JEGS/555/418...ErlEs_JPb8VRRFkW8iMjx0kzJ4yOXx4EaAkxLEALw_wcB

Of this one: https://www.summitracing.com/parts/...flfXhXT2TmcDWiYLbxVoFDCNe06V_LbEaApm7EALw_wcB

I prefer the second one. It's easy to calibrate and works when there's no GPS signal.

Joe

 

[4WDKC]

you need both as the ecm has to be able to read the speed in 4lo or it rev till the engien blows in 1st thinking its to slow for 2nd gear. The 91 3/4 &1 ton truck had an electirc speedo try to find one or buy from ebay. Another option is find a convertor from the output of the ecm to a cable driven for the speedo.

Others have swapped in thrid gen camaro speedo and or go aftermarket.

 

[Doppleganger]

Thanks fellas. I think I'm going to bail on the whole 4l80 swap. Too complex and expensive and I need a usable truck ASAP. Someone put 100k on this truck with a stock TH400....can do that - maybe just have it gone through. Even it needs all new linkage as the PO's fk-up son destroyed it too and no idea where to find that either. This truck is becoming a boat with the hole-money thing. Bummer.

The thought of selling off everything else (EFI, heads, etc) is starting to cross my mind too.

 

[Doppleganger]

Local trans rebuilder is a good friend of a good friend of mine. He's done these 'monster' 700's - has a couple that are in Vettes that are drag raced every weekend in the summer. Said they've been in them for 3-5 yrs with no issue.

Offered me one - a 92 (GM designated 4l60 - but last year for no electronics). Sounds promising - would at least make the truck usable without big $$$ for the time being. Dunno.