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  #11  
Old 01-19-2001, 09:56 AM
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Default Re: 4L80E Control Module/VSSB

Thanks Undertow - good stuff. ND/ME, unfortunately the 4L80 (not the 4L60) was introduced in 1991 to replace the TH400 and was computer controlled right from day one. There is no mechanical non-computer controlled version - so I am stuck in that respect. I would keep my speedo cable driven off my current T-Case.

Undertow, yes, thats what I meant. I know that in the '91-'93 diesel trucks the computer recieves no input from the engine. I am not sure if that is the case from '94 to '96? I got from your post that you say it is - that a computer from a pre '96 truck will work as a standalone? I think '96 was the year they changed to the OBDII system from the OBDI, not sure how that affects things either. The problem with the post '93 trucks is that they are fly-by wire - no throttle cable. I'm not sure how to get around that. As long as it was mechanically injected I can use a stock TPS. Keeps it simple. The physical transmission I would get would simply be a core from whatever year, preferably '93 or newer so it would have the upgraded hard parts and hopefully the stronger converter clutch. That way I can specify whatever internal electronics I want. The trans shop here local will do a custom rebuild for pretty cheap - which saves alot of other problems.
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  #12  
Old 01-19-2001, 12:21 PM
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Default Re: 4L80E Control Module/VSSB

I think you asked a very key question. What compnents/systems talk to the computer on '94-'95 trucks. With that answered I think you can plan appropriately. I don't know if the gassers from '91 to '93 (probably through '95 - don't quote me though!) talk to the computer or not either, but I know the tranys do (They're electronic!). I know without a doubt that the '96 and newer use OBDII, and (in the trany) you have the following sensors:
- Automatic transmission (AT) input (shaft) speed sensor (ISS) assembly
- Automatic transmission (AT) output (shaft) speed sensor (OSS) assembly
- Automatic transmission fluid temperature (TFT) sensor

BTW: I think the input and output sesnors are considered one assmbly, but not sure.

I think all the trany sensors talk to the computer, but those transition years (95, 96) raise that question: What kind of input are the computers expecting?.

Now, making some assumptions, I would think that all the 4l80e's have those sensors and would therefor need to interface with the computer to control the trany. That being said, i would assume any computer (year-independant)which can control the 4l80e should work for you (Also asuming that the answer to the question above was "All the computers expect the same input and send the same output").

If you can get your shop to build it with mechincal sensors (I have no idea if this is possible!?!?) in place of the electronic ones, then you might be in the clear for the trany swap.

And you do have the throttle cable issue to deal with since your not gonna be using a EFI gasser. Couldn't you just put together a throttle cable assembly in place of the electronic one?

Anyway, sorry for the long post. I find this type of swap to be very interesting and challenging, so I tend to ramble on.... hehehe...Led Zeplin...



The issue might be resolved if you go with a '93 computer and harness. But thats more money.


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  #13  
Old 01-19-2001, 01:13 PM
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Default Re: 4L80E Control Module/VSSB

Undertow, I know this - all 4L80E's have those three sensors and they are all electronic. The 4wd trucks have one speed sensor (input shaft) in the trans and one in the (output shaft speed) T-Case. Two wheel drives have both in the transmission. On 4wd the second sensor is not installed, neither is the reluctor wheel. There is just a block off plate. The sensor is put into the T-Case only because the vehicles use an electronic speedo - so it needs to see driveshaft speed - but the trans computer shifts based on engine rpm (input shaft speed). The computer uses the difference in readings between the two sensors to help control converter lockup.

So for a swap into an older vehicle, we can get around the T-Case and speedo issue by keeping the cable driven speedo output in the existing T-Case and having the trans shop doing the rebuild, install both sensors into the tranny like a 2wd. As I said the only reason its in the T-Case is for the electric speedo. This may affect lockup functions in 4lo but is unlikely, since lockup shouldn't occur in 1st or 2nd anyways.

If a truck has a TH400 now, then physically everything bolts up. The only remaining question is - how do you control it? Aftermarket computers are just way too expensive - the swap becomes not worth it. Maybe they will come down in price.

I don't know if there is a difference in gassers or not. But, with a diesel, chevy's were mechanically injected until '94. There is no engine computer. So any input the trans computer needs can be jumpered from existing sensors for that model year truck and engine. Cheap stuff. The other consideration is throttle position input - hence the need for a swappable TPS switch. Most '91 to '93 trucks with a 4L80E (3/4T's and 1T's) came with either 3.73 or 4.10 gears and typically a 235/85R16 or a 245/75R16 tock tire size. Sine I have 3.73 gears the chances are good I could find a match and the difference between 235/85's and the 285/75's I have on is very small - only 2.4mph variance. Not enough to really cause a problem with shift points and installing a TransGoII shift kit during the rebuild should take care of that.

The concern I have is if I cannot find a direct match - I would then need to jump the VSSB to correct for changes. How do I do that? Also, if a '91-'93 harness is not available - could a later module be substituted? And if so, can the fly-by-wire control be substituted for a standard cable controlled TPS switch which will work on a DB2 series injection pump vs. the DS4's PMD it wouild have been hooked to? The other question of course is - is there a difference between 2wd and 4wd modules - I don't believe so, but maybe.

Like you said - what kind of input does the trans computer need? In later years the fuel systems are computer controlled. So do the two systems interface? Does the trans computer need input from the engine computer? I have no idea. Hopefully someone here can tell us. Maybe you can? If they don't, then any harness and module will work. I have a strong suspicion that they do though.

A 700R4 swap would be very simple and easy. I researched that and I could easily have it in for under $1500cdn. But I don't believe its strong enough, and I'm not sure I want to risk finding out. I was advised by TCI and Hughes and several reputable builders around here not to do it. Other companies say it totally possible (you know who they are). They all want to sell you a tranny though. I do believe the 4L80E can be an inexpensive swap if one takes the time to look for parts. I was surprised at how cheap a rebuild was - a stock rebuild is really all I need, they are tough tranny's, I don't need a $3400US Hi-Perf rebuild. Even turbo'd and intercooled my engine will only put out 400lb/ft of torque.

Anyways, if there is any info on the control computers that would be great. And if anyone knows if the modules for gas trucks also work - let me know - we have a couple gas 454's and 350 trucks we'd like to swap as well.

Well, if anyones read this whole thing I wrote, kudo's. I'll buy you a case of Canadian Beer if you can answer my questions. (If your ever in my neck of the woods that is!).

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  #14  
Old 01-19-2001, 05:04 PM
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Default Re: 4L80E Control Module/VSSB

Well, I read it all! If I'm ever in your neck of the woods, you can expect me to cash in on that offer!

I think that finding someone who knows the interface well enough to shed any truly valvuable info may be dificult. Regretfully, I don't have the answers. I wish the service manuals I have applied to the years in question. I'm gonna try and get a local GM technician on the horn, see if I can get anything out of them. I'll post if I do.

I'd like to see the issues resolved and the swap work because I am considering the same swap if/when my 4l60E goes out on me (thats years away...I hope!)!

G'luck.


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  #15  
Old 01-19-2001, 08:14 PM
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Default Re: 4L80E Control Module/VSSB

quick headsup, locally trany guy went home already! Will try tomorrow.

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  #16  
Old 01-21-2001, 01:58 AM
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Default Re: 4L80E Control Module/VSSB

desiel,
thought you might wanna look at this (found it in some message here):
http://cgi.ebay.com/ebaymotors/aw-cg...item=545743362

Its a link to a Superlift VSSB for your truck. There is a link in the desc. for superlifts' website - I was thinking that maybe you could call them and talk to one of their techs about the swap your planning, they might be able to help.

No word from trany guy...yet.

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  #17  
Old 01-21-2001, 10:04 AM
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Default Re: 4L80E Control Module/VSSB

I could modify your VSSB to be fully adjustable for a small price. I don't think you ever said whether you were swapping this into a 85 with diesel or gas. If gas, why not simply swap in the ecm from a 93-95 truck with 4l80 along with the TBI, you would be better off in both manners. I believe the speed signal to the conputer is 40pulse- I would have to check for sure. Jags that run (jtr) www.jags tahtrun.com make a number of retrofit speed sensors for applications like yours check them out- If you have any questions on the VSSBbb email me gdkng@hotmail.com

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  #18  
Old 01-22-2001, 09:48 AM
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Default Re: 4L80E Control Module/VSSB

Thanks Undertow. GDKNG, the trucks a diesel.

Actually, pondering this on the drive home from work on Friday, I realized it doesn't matter whether the VSSB is correct or not. The 4L80 will shift according to the input sensor shaft speed which is directly related to engine rpm. A difference in gear or tire size would only mean that the vehicle speed would change - the only thing this would affect is the electronic speedo - which of course I don't have! So I am pretty sure any harness will work.

The local slavage yard has promised me the first one that comes in for $250cdn for everything. So we'll see soon enough!

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