Re: 4L80E & TH400 Tech.
 

So I have a th400 in my 70' c10 and I have the engine out for rebuild, and I want to do a couple things to the transmission before it all goes together. The truck is driven for fun, and should be around 400hp when I'm done with a 2600rpm stall :)) gonna be fun. I got a new adjustable modulator, a new filter, and a stall converter for the trans. I also got a deeper pan and autometer temp gauge.

I want to make the 1-2 shift as hard as possible (love it when the tires chirp and screach when it hits 2nd) and I'm wondering how to accomplish this without a shift kit. It would bark 2nd now and then before the tear down, but I want it to be consistent and much more firm.

I'm keeping the old fluid for the re-installation, and topping off with new if need be

Thanks guys
Matt

Re: 4L80E & TH400 Tech.
 

Block the 2nd Accumulator....The Inner bore is where the 2nd Accumulator piston rides, There is a feed hole at the bottom of this bore. Using a punch, Drive a .250" checkball into the feed hole below flush.
The arrow is pointing to the hole, I don't have a clear photo of the actual hole because I never thought I would have to tell someone how to do this... If you need a better picture? I'm in the middle of a 4L80E build & can snap a pic.
http://i296.photobucket.com/albums/m...ps7tynfn9a.jpg

Block the 3rd Accumulator like I already covered in this thread.


Drill out the 2nd (Red circle) feed orifice out to .200"
Drill out the 3rd (Yellow circle) feed orifice out to .200"
http://i296.photobucket.com/albums/m...psuyusnciy.jpg


********I DO NOT recommend doing this! You are getting the advise you want, Not so much what you need, When this trans breaks it's solely on you*********

Re: 4L80E & TH400 Tech.
 

Where do I get a checkball to drive into the 2nd accumulator? And how do I block the 3rd accumulator? Also how do I get the holes drilled to exactly .200"? Are you saying it's going to break because of how hard it shifts?

Re: 4L80E & TH400 Tech.
 

.250" checkballs are the standard size for all GM automatics, A local trans shop will have 500,000 of them laying around.

I covered blocking the 3rd accumulator in post 11.

A #8 .199" or #7 .201" drill bit will be fine.

Yes, The risk of Hard Part failure increases greatly with the way you want it to shift, The Intermediate Sprag will most likely go first if the Intermediate snap ring doesn't blow out.

Re: 4L80E & TH400 Tech.
 

Is there a way to have firm shifts and a 2nd gear bark but no hand grenade tranny? hehe

Re: 4L80E & TH400 Tech.
 

I will defer to Clinebarger for exactly what to modify, but while the engine is out maybe you could open the trans up and do the proper upgrades? Best to do it now while it's out of the truck, eh? I'd think you can have a pretty firm-shifting TH400 that doesn't explode. Lots of potential in that trans.

Re: 4L80E & TH400 Tech.
 

Just to clarify for my piece of mind, to do the "Dual Feeding the Direct Clutches" mod,
you do all the steps on posts 2&3 correct?

These three steps:
Use the Cup Plug to block the Reverse passage in the case.
Omit the lip seal in the direct drum.
Omit the second sealing ring on the Center support.

Re: 4L80E & TH400 Tech.
 

That is correct.

Re: 4L80E & TH400 Tech.
 

Clinebarger, this is an amazing thread! I stumbled on it looking for info to rebuild my 80.

I used to be a member but couldnt remember my password or email I had at that time, so forgive me for skipping the newb thread.

My question is. I have read about the dual feed and was wondering why some drill a hole in the drum when they do it, but you dont?

Also, what do you recommend to do as far as building mine to survive? I have a BBC that will make around 1200 on nitrous. I will not have a brake. Not a street car. I am going to use the electronics to control it, but wired for manual operation. Only shift 1-2 and 3 under full throttle, but would like to know how to make 4 strong enough to take a shift at WOT... Thank you!

Re: 4L80E & TH400 Tech.
 

Sure is! Wish we had even more trans discussion on this board. The tuning I've done in my posts above have really improved the feel of the whole truck.

Re: 4L80E & TH400 Tech.
 

It's not that a don't drill a Bleed Hole in the Direct Drum, I have & still do in certain applications.

Re: 4L80E & TH400 Tech.
 

What does it do, and would I need it for my application?

Re: 4L80E & TH400 Tech.
 

Hey Danger D, I'm just curious: Why not a TH400 if it's not a street car and you don't plan to be using 4th?

Re: 4L80E & TH400 Tech.
 

I have everything for the trans I have. Crossmember, converter, shifter etc... I also do want to eventually try to use 4. I want to attempt 200 in the standing mile.

Re: 4L80E & TH400 Tech.
 

If your revving over 5500 RPM, A .030" Bleed Hole in the edge of the Drum along with High Rate Direct Return Springs are required. These two things keep the Direct from "Soft Applying" in 1st & 2nd gears, Soft Applying burns the Direct clutches.

The Overdrive Sprag & Overdrive Planetary Carrier will not like WOT shifts into 4th with 1200HP.

CK has a Billet OD Carrier....http://www.ckperformance.com/View/4L...NETARY-CARRIER
HAS TO BE USED with a '91-'96 Overrun Clutch housing & Sprag! The Early OD Sprag is larger than the '97 & version.

You will also need....
Billet Input Shaft.
Billet Forward Clutch Hub.

These two are optional, But over 1000hp are Recommended.
Billet Main Shaft.
Billet Sun Gear Shaft.

Re: 4L80E & TH400 Tech.
 

How much setback should the torque converter on a 4L80 have from the face of the bell housing? I can't seem to get my trans and engine connected with out binding. It acts as if the converter is not fully seated but I've had it off and on 3 times, spin it once on the input shaft and I always end up with about 9/16" setback when I need about 15/16". http://i183.photobucket.com/albums/x...s79/image.jpeg

Re: 4L80E & TH400 Tech.
 

Keep on spinning it 'til it seats into the Pump, If the Pump Gear is installed Backwards....It will never seat.
The "Drive Flats" need to be offset to the Rear of the unit.

Re: 4L80E & TH400 Tech.
 

Starting to suspect my converter is bad. It is sliding on and engaging the pump detents but still won't seat fully. Once the converter is on the shaft I can spin it then take it off and see that the detents have moved. However it still won't slide back the last 1/2 to 1/4 inch. Also it feels like the guts of the converter are lose. It's guts rattle an awful lot.

Re: 4L80E & TH400 Tech.
 

I'm in the process of getting parts for a 12V Cummins/4L80e/NP205 build. I'm planning on using a 2wd version of the 4L80E because I've read it's easier to adapt a NP205 to the 2wd 4L80E because of the output shaft. The Cummins will be stock, but I want the trans to hold up to towing occasionally. When I have the 4L80E rebuilt, I'd like to do some upgrades. I'd like to do it myself, but I don't think I can. What up-grades would you recommend? Do you know of any reputable shops in Alabama that could do this kind of work? Would you recommend someone that has never rebuilt a transmission to try rebuilding a 4L80E?

Re: 4L80E & TH400 Tech.
 

I did TH400-to-NP205 years back and it was done with all stock parts. Very slick combo. I bet the 4L80E, being similar, will have a comparable option of parts. Can't help you with the upgrade part, though.

Re: 4L80E & TH400 Tech.
 

Mr. Clinebarger,
Me again. On the same 2003 Yukon/8.1/4L85E that I firmed up previously, I had also been noticing that the shift point RPM seems to be slowly increasing over the last couple years. Even at pretty light throttle around town, every gear seems to hang on just a little too long, and getting longer. Any idea what that might be and how to fix it? There has never been any electronic tuning to the truck. thx.

Re: 4L80E & TH400 Tech.
 

Ok I need some converter suggestions:
73 C10
5.3 w/243 heads shaved .025 to keep stock compression ratio
Lunati 60510 Cam 212/218 @ .050 262/268 duration Lobe Sep 113 531/531 lift
3.90 rear gears
28" tall tire
98 4l80e stock 97k miles

Re: 4L80E & TH400 Tech.
 

Don't need much for that build, The MOST Important thing to get is a GOOD Converter! Diesels are extra hard on them!!
Give Circle D Specialties a call....They will hook you up with a nice converter.

Build list....

Dual Feed the Direct Clutches as outlined on page 1

Replace ALL Bushings.

Run High Energy Frictions in the Forwards, Directs, & Intermediates! Borg Warner, Raybestos, & Alto all make High Energy Friction Modules. The Lo-Reverse Band has to be bought separately unless it comes in a kit...

Replace all Steel plates.

Replace the Pump Gears.

Replace all 3 Sprags/Roller Clutches.

Spiralock Intermediate Clutch Snap Ring, http://www.ckperformance.com/View/TH...UTCH-SNAP-RING

Actuator Feed Limit repair kit, http://www.transgo.com/products.php?...dcountview=Yes Does 6 Valve bodies...You guys building 4L80E's need to get together to spread the cost of this kit......

AFL Filter End Plug, http://www.sonnax.com/parts/2031-afl...lug-o-ring-kit

Large Ratio Boost valve, http://www.sonnax.com/parts/2170-lin...re-booster-kit

Line to Lube Pressure Regulator Valve, http://www.sonnax.com/parts/1989-lub...egulator-valve

TCC Regulator Valve, http://www.sonnax.com/parts/2025-tcc...ator-valve-kit

Torlon Check Balls (you need 8), http://www.sonnax.com/parts/1689-checkball

No Walk Case Busing, http://www.sonnax.com/parts/1981-case-bushing Requires careful installation, Cannot use a typical bushing driver...The bushing will break!

Re: 4L80E & TH400 Tech.
 

It is most likely NOT transmission related, It would trip codes if the "Shift Adapts" were maxed out.

Engine performance issues can & will cause the slow progression of later & later shifts, I have fixed similar symptoms with something as simple as a Fuel Filter.
Faulty/Dirty MAF sensor (Torque Rise is calculated by the PCM trough input from the MAF)

Re: 4L80E & TH400 Tech.
 

Give Chris at Circle D Specialties a call. Their in Houston.