NP 203 Married to a 4L85E

[dragstews]

Thought was to do a thread on what I'm in the mist of doing on my 75 K10 ..

Not very long ago I swapped rear ends ..
Truck came from GM with a 12 bolt, wasn't up for the work I was throwing at it ..
It didn't like being asked to pull a 30' fifth wheel RV with a 16' box trailer hooked to it ..
A trip to the boneyard netted a 14 bolt 3/4 ton (Light-Duty) Corporation ..
It came with 3:73 gear, 12 bolt was 3:50 gear ..

That was great for pulling, but gas mileage went out the window .. (Wasn't all that good to begin with)
My thought was to install a overdrive in a effort to gain back what was lost with the gear ratio swap ..

Wanted a super beefy unit due to the workload it was in for ..
The built TH 400 had no problem with the work, a great transmission to say the least about it .. Time for a upgrade was at hand ..

I bought a 2000 4L80E out of a 3/4 ton van from a boneyard ..
Being I was going to build it into a 4L85, with a host of Hi-Po upgrades along the way of assembly, gave me the basics .
Got it on the teardown bench and soon seen that it's been rebuilt recently .. That was a huge plus, although many parts was being replaced with the 4L85 parts ..

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Since I do powder coating in house, I thought what the @&# !!
Spent a bit of time prepping the casting for the powder ..
Then came the flood of Hi-Po parts ... I'm here to tell you that seems endless ..

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This kit ^ was a must have ..
And .... Carbon-fiber bands, wide H-D sprag, H-D second apply piston and kolene steel plates ..

Oh Boy .. Here we go off the deep end ..

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Started at the ass-end and worked up from there

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Installed a "No Walk" bushing backwards in the case in order to rollerized the 4x4 output shaft using a Torrington bearing from a TH 350C pump ..
That was one of many places in the build that got rollerized ..

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[nvrenuf]

What are you going to do about the tailshaft length?

 

[dragstews]

More Hi-Po parts was going into the build ..

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Extreme Duty 4L85E 5 pinion planetary geartrain assembly. The strongest 2.48:1/1.48:1 gearset currently available for the 4L80E transmission. Excellent choice for Humvee and high powered street strip vehicles.

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INTERMEDIATE Hi-Po,
This clutch set comes with 5 RedEagle clutches and 5 Kolene Turbulator steel plates. This is a 25% increase in the clutch apply area.

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Here's how it's adding up ..
5 in the intermediate
7 in the direct ...
7 in the forward
5 in the overdrive clutch

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Wasn't going to up-grade the forward clutch hub ...
Did intend to rollerize what was there ..

But after scaling it out and having a need to cut into the hub (Tool Post Grinder Time) for room, thought it would be best to get one already done ..
It has room for the bearing and has been made with .025" more meat ...

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Kind of a shame to hide billet parts deep inside .. !!

 

[dragstews]

What are you going to do about the tailshaft length?

I used a 4x4 output shaft ..
With also using a Oem 4L80 4x4 adapter and a special custom made adapter that converted the NP203 to the 4L80 4x4 adapter made it plug & play with 100 % spline contact ..

I'll post photos of this later on into the thread ..
Still at the moment yakking about how that trans is being built ..

More Billet parts are in the soup ..

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4L80E Transmission HD Billet Reverse Servo
Overall, the 4L80E is a fairly heavy duty transmission. One of its lesser points is the cast aluminum reverse servo piston. This weak link is prone to breakage while enduring the repetitive cycling that occurs in plow truck applications, when the boost valve has worn or when the pressure spikes. Adapt-A-Case's solution is this burly billet aluminum version. A direct replacement, it's much stronger than the OEM casting by nature. Their engineers have made an effective leap forward in design to ensure your customers' demanding durability.

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To overkill the rear servo I added this to the soup too ..

Sonnax Reverse servo spacer kit 34528-01K is a simple, low-cost way to add durability to the GM 4L80-E and 4L85-E transmissions and eliminates the need to retrofit early design Reverse servo pistons into late units.

Due to a design change in 1996, the Reverse servo piston commonly breaks because it is stressed more than early servos. Installation of this Sonnax kit reduces piston stress by increasing the contact area between the aluminum piston and spacer, and incorporating a cushion spring washer. The new contact area is over two times the original and the pressure between the piston and the spacer is reduced by 60%. This Sonnax kit easily installs during assembly and does not require machining or other modifications.

A word on the E part of 4L85 E

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Going to hide the controller inside the grove box on the sidewall .. It has built in a temp display that would come in handy to keep a eye on when towing a heavy load ..

 

[SquareRoot]

I can't imagine how going from 3:50 to 3:73 ratio made any difference in mpg.

 

[nvrenuf]

Definitely a cool build.

 

[dragstews]

Another add-on was this ...

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Case Saver Retainer​

Part No. 34762-20​

Fits '99-later 4L80-E.​

Sonnax case saver retainer 34762-20 for '99-later GM 4L80-E units is the only intermediate clutch retaining ring case saver that allows the intermediate band to be retained. This case saver fits over the intermediate band anchor lug inside the case and extends rearward to support the intermediate clutch backing plate retaining ring, preventing case lug blow out. There have been a variety of case saver designs over the years, however, all require eliminating the intermediate band as is often done in drag racing trans-brake applications. Only the Sonnax case saver retainer supports the intermediate clutch retaining ring, yet is thin enough to allow the intermediate band to be installed, allowing case lug protection in all applications.

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Trans went together super well, all was dialed into specks ..

Moving on to the install in the truck ..

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Since the trans came out of a 2000 Chevy Van had a problem with the dust cover ..

Wanted to beef the drivetrain with engine to trans struts ..
My truck never had them, but does seems like a grand idea to run them ..

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Those requires a dust cover with lugs ..
Got lucky and found one ... Only the 3/4 ton and up 4x4 trucks with rat motors used them .. Very short run GM had, 5 year run with a big block and 4L80 trans ..

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[CalSgt]

Those requires a dust cover with lugs ..
Got lucky and found one ... Only the 3/4 ton and up 4x4 trucks with rat motors used them .. Very short run GM had, 5 year run with a big block and 4L80 trans ..

When I first read this I was getting ready to argue that the braces (struts) are in all sorts of GMT400 trucks, then I realized you were talking about the dust cover... All of the trucks I was thinking of were 4L60 equipped small block units.

Cary on with the story...

 

[dragstews]

Trans is built, went though the 203 with R&R the bearings, replaced the chain and added a Mile Maker SS output shaft in turn converting to part time ..

Time to get those two hooked up ...

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Had thoughts of using the Oem adapter from the TH 400 ..
Would need some machining to fit the 4L80 case ..
And shorten the output shaft ...
Didn't want to mess with the shaft .. Already twisted a shaft that was in the 400 playing hard in the snow ..
Want to keep the beef with spline contact ..
So, acquired a Oem 4x4 adapter for the 4L80 ..

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Now that was the ticket ...

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Plugged right up to the 203 T .. Still needed a adapter plate that bolts to the T-Case and the 4x4 4L80 adapter ..

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This bad-boy did the trick ...
Super well made ...

 

[89Suburban]

Cool build, thanks for sharing.

 

[dragstews]

Things are progressing very well ...

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Time to stick it ..
And that is what I did ..

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Or tried to do ...
The GM adapters are a bit different between the 400 and 4L80 ..

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Got a slab of aluminum coming that will be used to fill the gap ..
Not here yet ...

And more modifying is needed in other areas in order to install the overdrive trans ..

This was a small one to do ..
The trans shift selector shaft was moved further back on the case than where the 400 was at ..
Had to move the shifter lever arm pivot on the frame for alinement ..

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Only needed to do this if using the factory column shift, which I am ..
I cut down a 75 Caddy Coupe Deville to fit
Used the wiring harness from the GMC, being both the column and the Jimmy's harness was GM all plugged up ..
Neutral safety switch, back up light switch was on the Caddy's column along with the gear selector ..

Another mod that must get done isn't as easy to do as the column pivot was to move ...

Gotta move the transfer case shifter ...
It can no longer bolt up in the stock location due to the adapters hiding the og bolt holes ...
Wouldn't work in the og location anyways cause it would be too far back in the truck's floorboard ..
With the 4L80's trans case being 1-5/16" longer than the 400 case is, plus the two adapters pushing the T-Case back a few more inches creates the need to go dumpster diving !!

Must fabricate a mount for the T-Case shifter, no ands, ifs, buts about it ...

Had a need for some metal to do this, and guess what said take me ?

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[dragstews]

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[nvrenuf]

If you can find a crossmember from a pre ‘85 K30 you’d close up the gap between it and that adapter foot a lot.

I gotta ask, why the 203? There’s obviously a pretty strong budget here so why not find a different / better tcase? Or are you intending to go with a 203/205 Doubler?

 

[dragstews]

If you can find a crossmember from a pre ‘85 K30 you’d close up the gap between it and that adapter foot a lot.

I gotta ask, why the 203? There’s obviously a pretty strong budget here so why not find a different / better tcase? Or are you intending to go with a 203/205 Doubler?

Did give some thought to using a gear to gear T-Case ..
But I already had the 203 and went though it not long ago ..
This old truck don't see much off-road action at all, more of a street rod nowadays ...

Should see a lot of hi-way miles yet to come .. Hopping that will be the case ..

 

[nvrenuf]

I get it. The 203 isn’t the most loved tcase but when their healthy they’re good.