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Sweet K30 or MEK5 please check in - VSS on 4L80e with NP205

Engineered Vintage

Engineered Vintage

IGOR
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So -

Bought a used 4L80E with driver side drop NP241 this weekend out of 3/4 ton '94 Suburban.

I know next to nothing about the 4L80E to date - all my experience is with older GM trannies (T350 & SM465) and what I've learned from reading on the internet

Question is:

This 4L80E has the two VSS sensors - similar to a 2wd 4L80E setup (as I've learned on here) It also has a VSS in the 241? Right?

Can I use the two VSS in the tranny, and not run one in the 205?

If so, will this work correctly - even in 4low? :dunno:
 
Early 4l80's have the two Speed sensors in the transmission case. They are ISS & OSS. The one on the transfer case is for you 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 nuetral & the transmission in gear.

If you are going to use it in your 72 K5 And retain the cable driven speedo, I think you would be fine running the 4l80 with no VSS in the t-case. Just use the ISS & OSS for your trans controller.
 
boz42 said:
Early 4l80's have the two Speed sensors in the transmission case. They are ISS & OSS. The one on the transfer case is for you 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 nuetral & the transmission in gear.

If you are going to use it in your 72 K5 And retain the cable driven speedo, I think you would be fine running the 4l80 with no VSS in the t-case. Just use the ISS & OSS for your trans controller.
Click to expand...

Very cool.

- for the record, I'm wanting to go with the option in your last paragraph (in red above). And maintain the mechanical speedo from the 205 to the stock '72 K5 gauges. So sounds like this will bolt in, then be a re-flash of the 8.1s PCM.

One other item of concern - in this write up: http://hotrodlane.cc/Streetstories/81 swap.pdf - which is basically what I'm doing.

On page 12 this guy mentions:

"...Transmission: I used the 4L85E transmission, which is the heavy duty version of the 4L80E, optional on 8.1 engines. Beware that not all 4L80’s and 4L85’s have an output sensor if they came in a four wheel drive application. Many four wheel drives use the speed sensor on the transfer case output. I found out the hard way and had to disassemble the transmission and install a reluctor ring on the output carrier. If your transfer case has a speed sensor, you still might have to change the reluctor ring if it was for a TBI engine. I used a New Process 205 transfer case..."

I'm thinking this is wrong - but wanted to get your guys' opinion - or now after reading it again - it seems like a moot point as I won't be running VSS in transfer case - :doah:

Any other thoughts? Thanks for the help!
 
IGOR said:
Very cool.

- for the record, I'm wanting to go with the option in your last paragraph (in red above). And maintain the mechanical speedo from the 205 to the stock '72 K5 gauges. So sounds like this will bolt in, then be a re-flash of the 8.1s PCM.

One other item of concern - in this write up: http://hotrodlane.cc/Streetstories/81%20swap.pdf - which is basically what I'm doing.

On page 12 this guy mentions:

"...Transmission: I used the 4L85E transmission, which is the heavy duty version of the 4L80E, optional on 8.1 engines. Beware that not all 4L80’s and 4L85’s have an output sensor if they came in a four wheel drive application. Many four wheel drives use the speed sensor on the transfer case output. I found out the hard way and had to disassemble the transmission and install a reluctor ring on the output carrier. If your transfer case has a speed sensor, you still might have to change the reluctor ring if it was for a TBI engine. I used a New Process 205 transfer case..."

I'm thinking this is wrong - but wanted to get your guys' opinion - or now after reading it again - it seems like a moot point as I won't be running VSS in transfer case - :doah:

Any other thoughts? Thanks for the help!
Click to expand...

I just put in a 2005 4l80E, never rebuilt, and it did not have the output reluctor ring. If its a 4x4 4l80E its going to have a plug where the sensor would go. You can just pull it and shine a flashlight in it. When you look in if you don't see teeth right smack in the center then it doesn't have one.

This is a good exploded view example of what it looks like. The one with the small teeth on top is the reluctor ring. The ring on the bottom may be visible from the plug hole by about 1/4 inch of it visible. This is not the reluctor ring.
34880-01.jpg


What 4l80E controller are you using? Everyone I have seen has a electronic speed sending wire. Also, which controller you use could determine where you need your VSS sensor at. I know the Optishift controller its best for the sensor to be mounted before the transfer case while the compshift controller i think recommends mounting after.
 
Early model 4wd's had both shaft speed sensors + a VSS. That is how my '91 4L80 is. I don't think that they deleted the rear speed sensor (OSS) on 4wd's until 96. Which ever year the vortec came out.

Too install the output reluctor ring does require a complete tear down. I have only seen one tooth count for the reluctor ring.

Yours has ISS & OSS so you should be set. Use those two sensors for the trans controller. Just use a 205 with a cable drive for your '72 speedo. Much easier to find as I am sure you already know.
 
kdoske - great picture you found there...

But Crap!

So I pulled the rear sensor - and now I don't think I have the reluctor ring in the rear OSS. Groan!

Front ISS:
IMG_5990.jpg

IMG_5987.jpg




Rear OSS:



IMG_5989.jpg

IMG_5988.jpg


So - your thoughts? :dunno::dunno:

And for the controller - forgive my ignorance - but can't I use the ECM from the 8.1? :dunno:
 
I can't answer any ECM questions newer than TBI stuff.

It does not look like you have a rear tone ring(RELUCTOR). That would mean you need to install one or run a VSS on your T-case.
 
boz42 said:
I can't answer any ECM questions newer than TBI stuff.

It does not look like you have a rear tone ring(RELUCTOR). That would mean you need to install one or run a VSS on your T-case.
Click to expand...

Thanks for your help - Sorry to beat this to death - I'm just trying to get all options on the table before making an informed decision.

That's what I'm thinking - my concern now is that even if I install reluctor ring in back of T-case, rig will shift funny when in 4low.

This brings me to putting VSS in transfer case by modifying 241 reluctor ring - but then I'm sunk with the mechanical speedo - unless I get one of these $325 gizmos: http://www.abbott-tach.com/Cable X.html

That seems consistent with info I'm getting?
 
There is one other option I know of for your speedo problem.

Ford made a VSS that had a cable drive built into it. It also came on some 205 t-cases so it might be possible to use a Ford 205 tailshaft on your chevy 205 & run the ford stuff. I have one of these Ford units but I am saving it for my Bronco project.

I am sure you would aso need to reprogam the DRAC.

Here are a couple of links about the part I am talking about:
http://www.ford-trucks.com/forums/754195-can-a-vss-also-drive-a-speedometer-cable.html

Rapter trans makes a signal convertor $90, about a quarter way down the page: #54MG & #55B - I have never seen these before
http://www.transmissioncenter.net/speedometer_calibration_______va.htm

About half the way down on that page is the Ford one I was talking about #9ss
 
Ah - good link!

So I called that outfit. He confirmed that to avoid 4low issues is to install the VSS in the transfer case - so that sounds like a done deal. Now to run the speedo he recommended this:


#350E. Kit to convert your TH350 transmission to an electronic speedometer. This is used when your vehicle has an electronic factory speedometer and your transmission was converted to a TH350 gear driven type speedometer. This kit consists of a 8 pulse generator and an electronic ratio adapter to adjust the signal. Can be used to drive a speedometer cable at the same time. Cost $247.00

_DSC3481.JPG
 
I hear you - I'm a ways off - and big Portland Swap Meet is next week - so I'll keep my eyes peeled for VSS with mechanical output -

My concerns with the Ford VSS though are:
#1 - finding it
#2 - will it work in my setup
#3 - is it a bolt in - or do I need to change threads on speedo cable or some other obscure thing?
#4 - will it work electronically with GM stuff?
 
IGOR said:
I hear you - I'm a ways off - and big Portland Swap Meet is next week - so I'll keep my eyes peeled for VSS with mechanical output -

My concerns with the Ford VSS though are:
#1 - finding it
#2 - will it work in my setup
#3 - is it a bolt in - or do I need to change threads on speedo cable or some other obscure thing?
#4 - will it work electronically with GM stuff?
Click to expand...


All good questions, I don't know those answers, I just wanted to point out that such things exsist.
 
why with the 2 sensors on the tranny only = bad problems in 4 low ?

its getting input and output signals. the multiplication is after the tranny what does it care ?

i plan on running mine with the 2wd 2 sensors in tranny and thats it.

plus the t case low ratio is 2.0:1 or 4.0:1 with my doubler kit. there is no option i know of in the computer to let it know the low or extra low and diffrent ratios.

mabye i have missed somthing but :dunno: you tell me if you know for sure . :popcorn:
 
I feel the same way about that as you de I can't see why it would make a difference. That is comparable to saying changing the rear end ratio will mess up the transmission.

Plus how much do you really plan on driving in low range. I mean I could see you hitting 3rd once in a blue moon, if you were in a mud pit. I can't see that you would use low range enough that it would matter.
 
rear ratio yes changes the shift points a bit . and speedo off spec if electric.

but who/what tells the computer the low range ratio and what to do diffrently. ?

and if swap in diffrent tcase with diffrent ratio how is the computer to know the diffrence ?
 
LOL - Aw hell. I don't know :D You make valid points

So - to sum up and lay this all on the table...

My goal:

8.1/4L80E/NP205, stock 1972 K5 Speedometer

To do this, as I see it, need the following:
1) Need ISS from transmission & OSS from either tranny or transfer case.
2) Need mechanical interface for speedo or "black box" VSS to mechanical converter

Option 1)
OSS from back of 4L80E

Upsides:
Proven technology on the 2wd 4L80Es
Maintain stock speedo cable from 205

Downsides:
From what I've read on the 'net - the 4L80E "shifts funny when in 4low without the OSS on the transfer case." - what this means, I'm not entirely certain - maybe one of you could elaborate? Does this mean it's hunting for gears or???

Further, my tranny does not have the reluctor ring, so I will need to tear down tranny to install it. Tranny is running good (if it ain't broke, don't fix it deal) This seems $$$ to me - as it is beyond my tech level, and will require tranny shop - to tear down and install ring - by that point why not upgrade/rebuild tranny too = $$$



Option 2)
OSS from back end of T-case by modifying 241 reluctor ring to fit in 205 & machine 205 case to allow sensor placement per MEK5's old post.

Upside:
Duplicates factory setup for 4x4 4L80E
No "weird shifting" -although again, please clarify what this means

Downside:
No mechanical speedo from t-case, need to find/buy a VSS/mechanical speedo interface


It is a toss up - but I'm leaning towards option 2 - (machining is readily available to me for cheap/free)
 
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