Re: 4L80E & TH400 Tech.
 

I made a mistake the 98 has just under 100,000 and I was also looking at a 03 unit with 80k and got the mileage mixed up. The 03 was sold before I could get to it.

Re: 4L80E & TH400 Tech.
 

Cool deal. Right now looking at it through tunerpro I have no pending codes, but that doesn't mean it's not worn. Something has **** the bed in the valve body either way, truck starts in 3rd and slightly binds when pulled into second or OD, rolls down the road and locks the TCC in third as programmed just fine. Best I can figure it's the "B" shift solenoid but I could be wrong, I'll inspect and clean everything. It is going on 26 years old so this is something that just happens. When its out I figured on doing the HD2 shift kit, new TCC, new shift solenoids, new filter screens, torlon check balls, and new 93+ force motor (as transgo instructs in their HD2) along with anything else that might need to be done, including an AFL fix.

Anyhow, if that gets it I'm going to be awesome, if not I'm going to need to get this thing completely gone through. I'll shoot you a PM.

Re: 4L80E & TH400 Tech.
 

Excellent thread. Helped me tune up my TH400 really nicely.

Now, how about a stock 2003 Yukon 2500XL with 8.1 and 4L85E. It has 116,000 miles, the trans "works" perfectly and there are no trouble codes... but it shifts so soft I can't stand it. It's a daily driver, so what would I do to just firm up the shifts? I'm about to go in for a filter change... can I just enlarge the feed holes a bit? I'm concerned the 3rd and 4th accumulator mod might be too harsh?

Re: 4L80E & TH400 Tech.
 

A Boost Valve & enlarging the feed holes will work, And....You are correct, Do not block Accumulators with a stock to 2800 stall converter.


For Non-Performance-Stock converter transmission orifice sizing, Do Not go bigger than a 50% "Area" increase over the Stock diameter! Shifts will get pretty rough if you do.

Stock 10% 20% 30% 40% 50%
0.040 0.042 0.044 0.046 0.047 0.049
0.045 0.047 0.049 0.051 0.053 0.055
0.050 0.052 0.055 0.057 0.059 0.061
0.055 0.058 0.060 0.063 0.065 0.067
0.060 0.063 0.066 0.068 0.071 0.073
0.065 0.068 0.071 0.074 0.077 0.080
0.070 0.073 0.077 0.080 0.083 0.086
0.075 0.079 0.082 0.086 0.089 0.092
0.080 0.084 0.088 0.091 0.095 0.098
0.085 0.089 0.093 0.097 0.101 0.104
0.090 0.094 0.099 0.103 0.106 0.110
0.095 0.100 0.104 0.108 0.112 0.116
0.100 0.105 0.110 0.114 0.118 0.122
0.105 0.110 0.115 0.120 0.124 0.129
0.110 0.115 0.120 0.125 0.130 0.135
0.115 0.121 0.126 0.131 0.136 0.141
0.120 0.126 0.131 0.137 0.142 0.147
0.125 0.131 0.137 0.143 0.148 0.153

**I have the chart spaced correctly in my reply, But the site will NOT take it without spacing it funny? I hope you can read it.....***

Re: 4L80E & TH400 Tech.
 

Perfect!
Boost valve like Sonnax 4L80E-LB1?
Any check ball changes?

Re: 4L80E & TH400 Tech.
 

Correct, Sonnax LB1.

No changes/Omissions to the Check Balls on any unit unless it has a Trans Brake & used for all out competition.

Re: 4L80E & TH400 Tech.
 

Is there a way to make the torque converter clutch engage more firmly?

Re: 4L80E & TH400 Tech.
 

Thank you for taking the time and sharing this excellent info!

Re: 4L80E & TH400 Tech.
 

Your chart came through well. Thanks. Some stock data if it's helpful:

2003 Yukon XL 2500 8.1/4L85E/4.1
1-2: .070"
2-3: .075"
3-4: .050"

The holes are so much smaller than I expected, I'm not quite sure what to do. Might just use your recommended .085/.093/.085.

Re: 4L80E & TH400 Tech.
 

A Sonnax TCC regulator valve with the (.300 OD spring) will firm up lock-up.
http://www.sonnax.com/parts/2025-tcc...1-instructions

I don't know how you want the shift feel, "Feel" being very subjective!

Here are largest holes I would recommend. Your truck is pretty heavy & can absorb a lot of shift energy. And you seem to want the shifts to be noticeably firmer.
2nd: .093"
3rd: .101"
4th: .093"

Re: 4L80E & TH400 Tech.
 

My assembly had no gasket for the 3rd/4th accumulator cover, but I see one on the exploded views. Is it OK to reassemble without?

Re: 4L80E & TH400 Tech.
 

The 3rd & 4th Accumulator housing HAD a gasket between it & the separator plate from the factory, And Yes, It needs one!!!

Re: 4L80E & TH400 Tech.
 

Here's my mod report. I hope this helps someone with a more stock build like mine.

First: THANK YOU CLINEBARGER!!!

Vehicle:
2003 Yukon XL 2500/8.1/4L85E/4.1 at 120K miles. Original owner. Started with a good working trans, just very soft shifts.

Mods:
Sonnax boost valve 4L80E-LB1
Sonnax TCC valve with the .300 OD spring.
Drilled feeds:
1-2: .070" to .085"
2-3: .075" to .093"
3-4: .050" to .085"

8 check balls in the original location, but I used Torlon balls that I had. There was minor/acceptable wear on the plate so maybe Torlon will slow this down.
No accumulator mods other than cleaning them thoroughly. There was a bit of the black paste that had "accumulated" in there. Otherwise, the trans really looked good. Almost nothing in the pan.

Before, the trans seemed to "work" fine and there were no codes, but you really had to pay attention to know when it was shifting. I don't like that in a truck, especially when towing. It also seemed to be getting softer and softer, but it's hard to remember how it shifted when new. Like I said, it's always worked and it's done a fair share of medium duty towing over the years with never even a hiccup (20 ft boat, motorcycle trailer, and a pretty heavy horse trailer).

Now, you can feel it, but it's still very acceptable as a daily and a people hauler. It could even be tuned to be more solid without sacrificing comfort. I made the largest change to the 3-4 feed hole to get it in line with the others and because it was the softest shift. They all feel pretty equal now. The torque converter clutch doesn't seem noticeably firmer on engagement, but it does seem to hold better. I swear it now runs about 100rpm lower on the freeway once it's locked up. Hard to imagine that it would have slipped that much all these years?

In Tow/Haul there is the usual slight increase in firmness, but still far from harsh. However, in 4Lo it's now a solid bump. Weird. If these mods had made it that firm all the time, it would have been too much. In the dirt in 4Lo it's fine. I wonder if the electronics firm things up in 4Lo.

Overall... I'm happy, but if I had to do it again, I'd go even larger on the feed holes. I was very conservative because I started with feeds that were much smaller than I expected. Going from .050" to .085" on that 3-4 really made me nervous... now I wish I'd gone larger. Seems the changes I made got the trans to what I'd expect from a good OE tune rather than the slush box I was driving. It's "on the map" now. I hope this helps someone.

Re: 4L80E & TH400 Tech.
 

Good job picklito!!! Did you see my revised Orifice sizes? I didn't expect those hole sizes either, But you have a SUV, GM might have done that on purpose.

Re: 4L80E & TH400 Tech.
 

I did see your revised sizes, but being my first time in a 4L85E I had no idea how large (or small) of a change I was making. Thought it best to be conservative. Although I still wish it were a little more solid, at least now it doesn't feel like it's consuming itself on every shift!

There will probably be no reason to ever go in there again (did I really just say that?). But what I might do is try some electronic tuning now. Do you have any insight on that?

Re: 4L80E & TH400 Tech.
 

I do not recommend increases in EPC pressure via a Tune with a large(r) ratio Boost Valve & Higher Rate PR spring.

Re: 4L80E & TH400 Tech.
 

Great information here. Bookmarked for future use...

One question on "Pressure Regulator & Boost Valve basics, From a Sonnax Tech article"
Is it better to just do the Boost Valve size increase?

Re: 4L80E & TH400 Tech.
 

When running a large ratio Boost Valve, The Pressure Regulator Spring cannot be over 15% stronger than the OE Spring....Anymore than that, Problems will surface particularly on the 4L80E.

Sonnax has Line Booster kits for both units that come with a Boost Valve & a 10% over PR spring.

TH400 part# 400-LB1
4L80E part# 4L80E-LB1

Re: 4L80E & TH400 Tech.
 

1970 TH400: I'm at .125" using a new plate from Superior and all 6 original check balls. I want to go a little firmer... enlarge the hole or start removing check balls?

Re: 4L80E & TH400 Tech.
 

Do you know what style Direct Drum you have...Roller Clutch or Sprag type???

A Intermediate Roller is quite a bit weaker than a Intermediate Sprag, A '70 model "should" have a Sprag type Drum.

Roller Clutch....NO larger than .125"! If you do.....The risk of Roller Clutch failure is high.

Sprag....You can go out to .140".....With the 2nd Clutch checkball in place & a Active 2nd accumulator.

Do not remove checkballs....The Reverse checkball being an exception when dual feeding the directs.

The checkballs job is to route clutch feed oil through the orifice, If you remove it, Feed oil will freely pass through both the orifice & the hole the checkball is suppose to check. You end up with a effective feed hole size of over .300" or larger.
I have fixed too many broke units with B&M/TCI shift kits (That delete checkballs) to ever recommend doing this on a street transmission.

The ONLY time I omit CB's other than reverse, Is on Reverse Pattern Manual Valve Body (RPMVB) units, And RPMVB with a Trans Brake. However these competition units don't take a standard plate, They only have the Feed holes, The CB holes are eliminated.

Here is a pic of a RPMVB/Trans brake plate to show the huge difference from a standard plate.
http://i296.photobucket.com/albums/m...psjofnsk59.jpg

Re: 4L80E & TH400 Tech.
 

I haven't been inside this trans but all indications are that it's an original 85k mile '70. Shifting so soft I doubt I'm close to breaking at present settings. I suppose the trans could just be tired but it sure works well otherwise. The only reason I'd firm it is so that it's not destroying itself.

Re: 4L80E & TH400 Tech.
 

Fixed it. Turns out that my new red-stripe modulator, replaced at the time of valve body work ONLY to avoid a problem... was the problem. The female threads in the modulator were not tight enough on the adjustment screw, allowing the screw to be pushed out. I'd go in a turn, no change. In another turn, no change. Finally I noticed that the tip of the adjuster screw was always flush with the hose nipple. Fixed the threads, turned it in intentionally too far to clearly demonstrate whether this was the problem... and they all lived happily ever after in Turbo 400 Land. So...

.125" on both feeds, 6 check balls, accumulators unchanged. 1-2 is about right, 2-3 could easily be .140-150" and be very safe. Don't think it's important enough at this time to go back in there.

Clinebarger... do I have to say Thank You yet again???

Re: 4L80E & TH400 Tech.
 

Great detective work picklito! I generally do not advice adjusting a Red Stipe Modulator.....But in your case, You may not have caught this without fiddling with the modulator, All I can say is Good Job!!!!

Re: 4L80E & TH400 Tech.
 

I am hoping for the best but planning for the worst:
98 4l80e just under 100k, very little metallic "dust" in the pan and the fluid seemed ok when I drained it. It is currently installed in my 73 with an 04 5.3 in front of it to replace the tired th350 that was in it. I want it to work just fine but in case it doesn't is this a transmission that I can rebuild without any prior experience rebuilding transmissions? I would rather do it myself to save the extra money for a good converter.

Re: 4L80E & TH400 Tech.
 

In my opinion they are easier than 700R4/4L60E units, Think of it as a TH400 with a few more parts. I have a few tricks to make it easier on you if the time comes.