M1031 - 4L80E conversion ??s

[CCATLETT1984]

Re: RE: THATS THE RUB...

I think TCI transmissions makes a stand alone electronic controller for the 4l80e that you can program for shifts and it also allows calibration of the speedometer.

yes they do, but it still needs the VSS imput

the only way around that is to go with a full manual valve body, like the one that transgo makes, with it you dont need any computer, but you have to shift it manually of course.

 

[Ambulancechser]

it'll work...

it works, but (there's always a problem...) when you use the manual shifter kits,you are essentially creating a manual shift thm-400...the trans will need some way to sense vacume much like the 400,to help control line pressure and shift points.unlike the 400 the 4l-80 has nothing resembling a mechanical governer.without PRECISE control of vacume in relation to throttle position,the line pressure in the 4l-80 will be hard to control...much like haveing a maladjusted TV cable on a 700-r.this can very quikly lead to a burnt trans when used in an all around street / trail rig.

The vac pump on the 6.2 will supply the vacume,but the vacume controller on the IP is not really precise enough to control vacume for the 4l-80.add that to the fact that the line pressure in the 4l is normally controlled by a solinoid,which itself is normally controlled by the tcu...and you suddenly have to mod the line pressure controller in the trans.(it's just behind the pump in the 4l-80...just a piston.)this means trans dissasembly,the apropriate kit and parts,precission reamers for the piston bores,and the skilled person to do the job/set-up/test.

The trans was designed to be used under computer control.full manual is really only a race thing.if i was using a 4l-80 exclusively off-road or at the trac,it's exactly what i would do.i'd also have a spare trans to replace the first one when i burnt it out after a few weeks.besides...a manual shift auto usually shifts hard enough to snap your neck.regardless of speed or throttle position.not fun for a daily driver.

Heres a few pics by the way.the difficulties remaining are trans lines (got to get a decent tubing bender),shift linkage(i can use the 400 linkage with a bend or two) and the TPS.turns out that the tps from a non electronic db2 will bolt to an earlier db2 with no trouble.trying to find a used one, as new is over 120$...ick.as for drive shafts,the front will have to be shorter,the rear longer.seems the np-205 is shorter and more compact than the 208.found a front shaft from an 80' suberban with a 205,that will fit perfect,just need to clearance the c/v for a little extra angle.

 

[Elohim1]

Does the NP205 which is found in the 91 crew cab, behind the 4l80e have 32 spline output shafts?

 

[peyton]

I've got a 95 chevy 3/4 ton 4x4 that was a diesel and was converted to a 350 gas, unfortunately they left the diesel 4L80E in it, they did "something" to the wireing to make it shift, but the RPM ranges are all wrong, has no power....thing is tuff as all get out though, I kicked the snot out of it for over a year and it laughed at me. I'm am in the market for the "correct" 4L80E to replace the diesel unit with [ and a fresh shortblock ]...anyone need a diesel one ?

As I understand it (caveat emptor!), the torque converters for gas and diesel engines have very different stall speeds. If your 4l80e still has the diesel torque converter, perhaps it is causing shifts in the wrong power bands.

Peyton

 

[CCATLETT1984]

as stated above, if your truck still has the diesel stall converter, it will shift and run like a dog, my buddy swapped a sbc into his m1009 and didnt change the TC or the governor on the trans, and it shifts way out of the power band for the gas engine.

 

[smalltruck]

On the T-case to trans adapters talk to Kyle at Northwest Fab Works. He stated on another forum that he was/is building that adapter to do this swap. My understanding from that post was that he was using the more common figure 8 or racetrack 205 and installing the 32 spline input shaft. www.northwestfab.com

On the controllers compushift makes a stand alone controller that doesn't need a laptop to tune it with. Supposedly there are some factory standalone computers from 1 ton vans and bread trucks. Year models were 92~93 only IIRC. www.compushift.com
Hope this helps
George

 

[86m1028]

Does the NP205 which is found in the 91 crew cab, behind the 4l80e have 32 spline output shafts?

Rear output is 32 spline.
I will have to check, but I believe the frt output is 30 spline.

 

[jimmy-90]

In responce to truck0590. What you need is one of these. This is a billet adapter for a 2wd 4L80e to a figure 8 style np205. Wish your th400 worked good then we could barter and haggle since I live in the next town down from you and am looking for a th400.

 

[mtjbrown]

I've been considering this swap for my civvy truck. Any idea what the total cost will be once you guys finish? I figured it was going to take me quite a bit of my own time and probably $2000+ in the trans/computer/misc parts/machining/labor to do it.

As was pointed out, the 4L80E/NP205 adapter was a one year only item, but a round pattern TH400 adapter can be machined to fit. You have to shorten/lengthen the drive shafts, but also the PTO drive and the shifter controls, too. Combine all of this with the fact that I just don't have the time to hunt down all of the bits and pieces anymore and I'm considering just spending a little extra and getting a Gear Vendors... Since it's a crew cab, I don't have to worry about too much drive angle change by shortening the rear shaft. Then again, I keep asking "Do I really NEED overdrive?" and the answer is always "No, but it would be nice." I just haven't decided if it's $3K worth of nice or not...

Here's another thread from BC4x4 about the swap, but I think the points brough up here echo it...
4L80E questions.

Be careful with the gear vendors unit. A friend of mine bought one brand new, backed out of a parking space 2 mos. after installing it, no pulling when he shifted into drive. Gear vendors would not warranty it as they state not to be used in reverse!!! Supposed to barely move backwardsa then bump tranny into neutral and let it coast. He had to pay 1700$ for a new drive unit. UNBELIEVABLE for a 3 grand piece of %&$#!!

 

[mtjbrown]

In responce to truck0590. What you need is one of these. This is a billet adapter for a 2wd 4L80e to a figure 8 style np205. Wish your th400 worked good then we could barter and haggle since I live in the next town down from you and am looking for a th400.

Hey Jimmy, this piece will allow you to bolt a 2wd 4l80e to a NP205?? Then you have to fix up a tps input and speed sensor output plus a computer, is that right?? The reason I ask I know someone who several mid 90's GM p/u with the 6.5 turbo. They have 4l80e for 600$

 

[jimmy-90]

Yeah thats what you need. There's places out there that will build you a 4L80e with all that stuff and then buy a compushift. Originally I was gonna put a 4L80e and that np205 in my civi blazer but I got carried away and it kinda turned more into a competition vehicle. I still need a trans for it but im thinking th400 now just because it's alot cheaper and I don't really need the 4th gear for mud raceing and boggin.

 

[cjtroutt]

Hi the 4l80e can be installed right to the T case the rear trans out put shaft eill half to be pulled out and install shaft that stick out 4.500 in out the rear of the trans where it bolts to the trans for the np205 to work the 4L80E is aprox 1.750 in longer than TH400 trans
32 splin out put saft compushift build an stand alone computer for the 4L80E but make shure that you have both sensor set on the trans. And also youn will need the an cable TPS sensor that extra for this converson.
Ith is best to buy an 4x4 4l80e to start with less mon out pockit.
My pref would be an allison 2000 & np 261 transfer case just re clock it the computer will be bought on Ebay around 150.00 or less and will need an wire harnis.
analog TPS all items could be bought at Detroit Diesel Allison automatic Dealer
the trans will BE an 6 speed and bolt to the chevy alot beter the over drive will .62% unlike 4l80e .74% OD.it will be costley both ways.
This op build Th400 pickup 203 T case make an 50% od by flip it over in sted of dubbler.
203 to 205 t Case advance adapters has this on there web I done one this way and it was kool it will act as you have 3.07 Gear set or better no problem cruse ar 70 + mph and not over rev the engine.
sorry my spelling might be bad I am worn out.

 

[dstang97]

can you go into more detail about the 203 combo. I have never heard about that.

 

[2deuce]

I bought a 4l80e last night because the price was good and I got everything that went with it(or can go back for it) for the 6.5 diesel. It is a 93 model. I have read this thread, but its not completely clear if I can use the control box or need a stand alone box. Its from a 93 2wd pickup. I have the engine wiring harness with the connections to the box, but not all the under dash harness because I didn't think I needed it or the linkage to the trans thinking I could use the th400 linkage. The list of what I got with the trans is:
flex plate,
torque converter
engine wiring harness(no throttle sensor)
control box

The owner of the truck is a real nice guy and said I can return and get whatever else I might need in the next 2 weeks or so before he scraps it. Is there anything else on the truck I should get? It was a low mileage truck that the owner bought for the engine.

Thanks,
Greg

 

[acmunro]

Just jumping on board here. I'm looking to do the swap. I have most of the stuff gathered.

 

[cjtroutt]

can you go into more detail about the 203 combo. I have never heard about that.

Hi the 203 is gear set is reversed & it is now an over drive unit this is also used in quad plexing transmission in semis rigs I had 1 W900b KW & fliped the ladt two gears and wow la OD was in works an good transmission shop or old timer that builds them will be the man for the job.
All it call is gear reverseing to get over drive .74 .63 .50
hope this will help.
The Transmission shop I use can build such an anmial has lots of exp. with 4x4 from small to FWD.

 

[dstang97]

can you shift the np 203 going 50 mph to get the overdrive? or does it have to be in in high at low speeds?

 

[cjtroutt]

NP203 has to be in gear when starting out for hwy.
this system is like have two speed rears.

 

[POOR WHITE BOY]

I have a 1991 v3500 with the 4l80e and np205 combo. I have also installed the same combo in my 1986 m1028. If you need any photos or correct part numbers for the swap . Just send me a pm

 

[Samyguy]

Hey CJTROUTT !!
can you post up any more on this NP203 swap??
Does this replace the NP205 or is it in addition to the NP205?
Are there any drive shaft mods. needed???

thanks