The Good, the Bad, the Ugly, 4L60E 2-3 shift

The characters, a 2002 GMC 1/2 ton Sierra,4WD, Xct cab with a topper. 5.3 engine, 4L60E, cammed, mid-lenth headers, electric fan and a tune. And me, an old mechanic that has overhauled many trannys, but that was years ago and this was my first one with an E behind it.

First I want to thank all the posts on this forum that I used to rebuild my tranny. I almost got it right.

THE UGLY

A clamp that I used to connect a cooler broke and I lost all my fluid. I did not notice that the inner part bent up putting pressure on the bolt. I used a fuel line clamp. The clamp lasted for about 12 years when I put the cooler, Sonnax Super hold 2nd and 4 th gear Servos and a transgo 4L60E HD2-C shift kit. I refiled the tranny and fixed the clamp.

It ran another 300 miles, then it lost 3-4 gears. I was 400 miles from home and had been away for over a week so I drove home in 2 nd gear—40 miles per hour. I think the 3-4 pack was on the way out because sometimes it would act like it was in neutral when upshifting 3-4 but would final grab and go. I did not know then that 4-2 WOT shifts were not good but ugly.

THE GOOD

A Yank Truck Thruster 3000 converter that should flash around 2600rpms---only have 125 miles on the rebuild so I have been driving it easy

Borg Warner over haul kit, added one more 3-4 friction plate and six .076” 700R4 plates and the stack set at .040” clearance.

New Borg Warner spags.

A teflon pump bushing- which is good because it fit tight on the converter hub that aligned it to the flex plate.

Sonnax:
Shift - Performance Pack HP-4L60E-01, with the TCC pressure limiter.

Drilled the factory plate per the instructions, .093” for the 3-2, 2 nd shifts, 3 rd, 4 th clutches, and .055” for the AFL balance..

Heavy Duty 2-3 Shift Valve, Replacement seal kits for the servos and after talking to Sonnax set the pin clearance to .125”.

Input Drum Reinforcement kit and a SmartShell. The SmartShell gave me a spin. It changed the gear stack from .018” to .035” because of the different way it loads the parts. So after talking with Sonnax I came up with a .025” copper shim with tabs to place between the bearing and the inside the SmartShell to end up with .010” clearance. The input endplay was set up at .016” which was good because it was +.005” more than the gear stack.

I was going to Red Locktight the Input drum-shaft but my home made press made for pressing silver logos was too short. So I cleaned the spines and used Permatex Green threadlocker which penetrates gaps in assembled parts, which was good.

I took out the Transgo shift kit, it came with a predrilled separator plate that I ended up peening down the 1-2 shift holes from .082” to .073” and the 2-3 hole from .093” to .088” because the shifts where too hard,making the holes smaller helped. And it clunked driving in town when coasting and I think upshifting.

THE BAD

Everything worked good except the 2-3 shift, it is slow and makes my head move forward as it makes the shift--- but no flaring. I talked to Sonnax and did what they said. Had my tuner send a new tune checking on the shift, nope, not better. Did a line pressure test, drilled a hole in floor board near the gas pedal to get at the port because it is covered by the front drive shaft. Pressure is good; 70lbs at idle, 90 lbs in reverse, 300 lbs in reverse at a blip, about 180 lbs in drive, 110-130 lbs when the 2-3 shift occurs. Then I replaced the 2 nd gear Super hold servo with a Corvette style. Then I redrilled the Servo release check valve to more than said, to .140” which should of negated the valve, I should of left it out.

After reading that too short of the servo pin can cause mistiming of the 2-3 shift, I welded up the servo pin for a clearance of .075.”



FINALY THE END, to be continued, like at bad movie—

The 2-3 shift is better, but I still have a slow 2-3 shift; it is ok when driving with light throttle but under medium acceleration there is still a pause and my headshift-o- meter still bobs forward. As I am still in the break in period for the converter I have not WOT it.

The other shifts are clean and quick, firmer than stock but not hard. I know that the band releases then the pressure engages the 3 rd clutches, the 2 nd servo is the accumulator. Thanks for watching this boring flick.

Does anyone have any suggestions on how to make this bad movie any better?
I sure would hate to pull the tranny out again.

 

I am guessing that I should open up some separator holes.

Below is what I have now for the sizes.

Which one is the band release hole? A?

Which one is the 2-3 shift? D?

The Transgo drill holes include a larger .093” sizes for the F, C and G holes, what would you recommend there? Would removing the Sonnax 1-2 Accumulator valve shim help, the 1-2 shift is good.

What would you recommend for my application for the slow 2-3 shift? And did I miss any?

Thanks in advance.

A 3-2 shift now .093”

B 2 clutch now .093”

C stock

D 3 clutch now .093”

E 4 clutch now .093”

F lub? now .055”

G AFL balance now .055”

 

I would try removing the Sonnax servo release check valve first, before doing anything else.

 

I did drill the hole out and tipped the drill bit to make it bigger yet, maybe about .140" in size. I do not know how large the factory check ball hole is but I think it is smaller than that.
But you are right, I should of left it out, my bad. Going to check on all the possibilities before dropping the pan again.
Thanks,
PS, the Sonnax check ball is above the feed hole in the valve, I do get how that is supposed to do anything. The hole size which was .100" would restrict the flow.

 

Have you checked if the servo checkball release in the input drum is seating. These are rarely replaced in rebuilds and can get debris stuck in the preventing seating causing a substantial leak in the 3-4 clutch circuit , You can check this by air checking the drum through input shaft clutches loaded of course the ball is visible and should pop up and seal very close to if not totally air tight.

 

Hello, Yes I checked in the assemble stage through the input shaft, next time I have the valve body off I will check it on the case. But the bleed orifice will be "leaking."
I am curious to know if the hole I drilled out to around .140" in the Sonnax servo release check valve would still be restricting flow in the 3rd accumulator circuit?

 

While the consensus now is to not use the Sonnax Server release valve, I still have it installed in my current trans and the 2->3 shift is still super fast.
My 3rd feed hole (D in your diagram) is either .101 or a bit bigger; lots of people drill it to .125 without needing other mods.

Yes, when air testing the input drum, the bleed hold near the input shaft will leak, but you should be able to hold your finger over it to listen for other leaks. (At least to 40psi or so)

 

Thanks, the 3rd feed hole will get drilled sooner than later. What would you recommend for the Lub hole [ F]?

 

Holes F and G are typically drilled (if not already) to .093.

 

Hello mrvedit,
Yes the shift kit Transgo does recommends those sizes, Sonnax performance pack just recommends to drill hole G to .052" and F not to drill. The stock Lub F is really small so I did go .055" on that one and G.
I ordered Sonnax end plugs and 2 abuse valve kits so when I install them I will be drill G, F to .093" and try 3rd feed hole D to at lest .101".
All so, I am going to ask Sonnax at what size, in their Servo release check valve,that opens up and negates the valve. If .140" does negates it, then I now for sure that D needs to be larger.
Thanks for answering my question.
Finally have 150 miles on the Yank converter, yesterday a new Toyota truck beside me at a stop light took off to show how fast his truck was. I did not even have to floor the gas pedal to get out in front before I hit the speed limit and stop accelerating. Driving 150 miles with out getting close to WOT sure has been along 150 miles!

 

I'm not a pro builder, just a hobbyist who likes to experiment a lot. While I have tried the Sonnax Performance pack, even then I drilled the separator holes to larger Transgo sizes.

I suggest not drilling D (3rd feed hole) bigger than .125 because I recall PBA saying that some other mods had to be made then too.

 

yup, I talked to Sonnax, they said I should experiment with larger hole size on the 3rd feed. So when I get my parts I will remove the servo check valve and drill the 3rd to .101 for starters, it is at .093".
Will keep you posted, thanks.

 

With ours we do this, First 8 frictions with the thickest steels we can fit , Make sure the apply and backing plate are perfectly flat by running them on a stone any high or low spot will burn through every steel and all the frictions. We replace the helper release springs with springs with a higher spring rate but lower tension we have also noted in a couple pressure related 3-4 clutch failures they do not collapse like the factory ones when they get hot. We use a .093 feed you can go to .110 3-4 fee hole but will mostly only make the part throttle 2-3 more aggressive. we do not enlarge the servo release (3rd accum feed) nor restrict it this is an area you have to be careful not to change much as you have the band releasing and the 3-4 clutch applying . To much overlap you will burn the 3-4 clutch to little you will get a rev slide bump and also burn the 3-4 clutch.

We set dry clearance at around .020 on the 3-4 once applied this opens up to around .030 to .035 after a run on the dyno we have noted which is IMO perfect some may disagree but its worked perfectly for us.(Note if using the release cages check clearance with them installed. I do suggest using them)
Double check that the 3-4 piston release valve in the input drum is not leaking. We see that from time to time debris not allowing it to seat this will cause a delayed sliding apply low pressure and eventual 3-4 clutch failure no matter what the feed hole size is. You may be able to clear it blowing back through it with air but the stock replacement is only a couple dollars and the sonnax a couple dollars more it knocks out and back in easily with a punch .

Line rise is most important though the exact numbers vary with different regulator springs, Boost valve sizes and even PR SOLENOIDS it should rise steady as throttle increases in a pretty linear manor with the throttle starting at 90 to 110 lbs and topping at around 220-230 ideally by wide open throttle .

Debris or damage in the servo release check ball in case are common if its a core or unit that had a lot of metal in it so check it very carefully for debris and rust. I have used the sonnax valve to replace it with good results though prefer the stock set up personally.

Make sure the green oring in drum has not been cut or damaged when installing the forward clutch as this will allow forward clutch oil to partially apply the 3-4 clutch resulting in quick burn up.
One way to see if you have a leak at the accum check ball in case while trans is in car is with a pressure gage in while sitting still in drive force 3rd gear from second you should see a momentary flick of the gauge but returning right back to where it was.
Using larger feed holes for 3-4 apply is fine however will not solve a leak problem will only result in a faster apply to slip rate lol.

Be sure and use the servo return spring as the band / 3-4 clutch overlap on the 2-3 shift will also burn the frictions and cause faster failure. Some remove this as a way to decrease 3rd accumulation rate but not a good idea we in fact use a stiffer spring here which also aids in the release of the band on a 2-1 manual downshift roll racers do a lot making a smoother downshift transition from 2nd to first.

While good quality frictions are of course important and which type is best many will argue in fact the hydraulics of the 3-4 is the primary thing that will make the difference between a long lasting or short lived 3-4 clutch set.

Hope some of this information is helpful Sorry if a little disorganized as I was just typing all I could think of as it came to mind.

 

Thanks Performabuilt,
Thanks for the information-----
I will let you know what happens.

 

Yes, thanks PerformaBuilt.
From that description we can learn that it doesn't take radical mods to build a strong 4L60E, just attention to detail, especially any place the 3rd feed circuit can leak, and careful preparation and assembly of the 3/4 clutch.
Interesting and new to me was how much the 3/4 clutch clearance increases after the first run.

 

The amount is opens up depends on the frictions used so varies but is substantial I would guess from the compression of them at 230 psi and the caged helper return spring play a lot into it also I have seen many times checking clearance without them was to tight but with them was just right.
I think the additional pressure pushes the apply piston tighter against the drum.

 

Thanks to performabuilt for always sharing good info and experience.

I think this is the most important part of mrvedit's post in red. You can drill whatever hole size you want, use the best clutches in the world, but if there are massive circuit leaks...you're still going to have issues with the 3/4's plain and simple.

-Since I've started vacuum testing...Rev. Abuse bore plug and o ringed end plugs are a standard part of every build!!!

-I usually have a couple teflon ring'd servo pin cores on hand so I use them also

-O-ring boost valve is good, i've started to see some extra wear there when vacuum testing.

-Also, eliminating standard shift fluid wastes is good...if you race in d3, the HD2-3 shift valve is good to keep the overruns applied so that they don't rob oil on the 2-3 shift.

Performabuilt is dead on with the pressure I like to see as well. 220-230 is a very good number

 

interesting you note the servo pin bore , Something we have noticed new cases 05 up seem to be more likely to have excessive leakage and wear in the bore than earlier I am not sure why this is but something I have noted .

 

1st I want to thank every one that took time and offered advice, it was good and helpful.
I received the 2 Sonnax Forward and reverse Abuse valve kits and the O-ringed end plugs today. I do not think that was the problem but it made dropping the pan again---less painful. There was some scoring on the old plug ends.
I took out the Sonnax servo check valve and drilled out the 3rd apply hole to .101." [D on the plate picture]
The stock 3rd accumulator check valve was moving when I air tested it and I did tap it with a punch.

I gave it a long test drive and the 2-3 shift now is good. No more headshift-o-meter bob forward and a quicker shift that is not harsh.
So I can take a 350 mile trip and an pick up my small camper that I left at a ranch after hunting season. Also I will be putting on a short class on hand engraving that a student of mine has gathered six people together, out in the badlands where my camper is parked.

Just have one more question; somewhere I read that I should not do WOT downshifts from overdrive 4th to 3rd, that it is better to shift it to manual 3rd and then punch it? I do have the HD 2-3 shift valve which does not do anything in OD [4th].
And in the past I have hit 2nd from 4th in WOT, what are your thoughts on this?

It is good that the old rust bucket is running again. Some day I will share all the areas that I have been fighting rust on it.
Thanks again.

 

I go from 4th to 2nd all the time. Will it break ****? Maybe. Do I care? Not really. Is it worth it to see my passenger's head snap back when I do it? Definitely

On a serious note, I've heard the same thing. I think it has to do with the gearing ratio change between 4th and 2nd. The drop from 3rd to 2nd is much less drastic and, therefore, less of a shock to the transmission. So, if you really do care about preserving your transmission, drop it to 3rd first.