All my shifts feel very good at light throttle and at WOT. However, at medium throttle, 2-3 kind of feels like it's happening in two steps. After reading a little, it is pretty clear that the band isn't releasing fast enough. I built this thing and it works great, but there is still a lot that I don't understand. I have the Alto pwer pack 3-4 clutches. Clearance is about .025". I used all of the high rpm springs from transgo. I have sonnax 2nd and 4th super servos, the servo check valve, the spring loaded input drum check valve etc. etc. etc. I would like to correct this problem before I burn my band up or worse. In your opinion, what is the best way to get the band to release quicker? Obviosly I'd prefer to do it from inside the pan and not have to pull the pump but if that's what needs to be done then so be it.

 

Do you remember how big you drilled both the 2nd and 3rd feed holes in the separator plate?
What is your current servo end play?
Do you have the Sonnax servo release check valve installed?
If yes, did you remember to drill the passage in the valve?

Once we have your answers, I hope that carlsonauto or other pro builder can answer your question and/or give suggestions.

 

I have 2nd at .093 and third at .110 if i remember correctly. Someone told me to put it at .120 but I think I chickened out. My servo clearance was on the high side but in tolerance. I do have the servo check valve and drilled it like the instructions said.

I've heard of using a stiffer servo spring. That would certainly be an easy thing to try. Otherwise I hope to be able to modify the separator plate, even get a new one and start over. Here's what I have in my phone. I think I drilled them all like this but a little smaller on the 3rd.

I put this thing together but I still don't understand it. Where can I get a breakdown of what happens during each shift event?

 

The servo is released by the 3rd gear oil pushing it off.
I've never had ANY success using the Sonnax servo check valve, for some reason it doesn't work with what we do.
A stiffer servo return spring may help, but you could possibly be dealing with a slide bump not a tie up and that is a servo coming off too fast.

 

You are not the first one I've heard that from. I think the first thing I'll do is remove the check valve. Would you mind explaining what happens with a "slide bump"?

It's pretty hard to describe what I'm feeling with the shift.
Just feels like it's happening in two steps and it almost feels like it slows me down during the shift like torque management. I tune my own stuff and there is no torque management being applied. Also, raising the part throttle pressure doesn't seem to help but lowering it may have helped a little. I need to do some more testing. I have not put a gauge on to see what pressure I'm actually getting. I don't think that fooling with the pressure is the right way to fix this.

 

I always recommend tapping (5/16") the Sonnax servo release check valve before it is installed. Then if you do install it tightly with the optional o-ring, you can still remove it by screwing a bolt in and pulling it out.

Lots of builders drill the 3rd apply hole to .120 and don't bother with the servo release check valve. So, your .110 size should not be a problem. However, if you want to try smaller sizes, I bought an interesting "valve" on ebay which is like the Sonnax valve, but doesn't have the checkball. In fact all it has is a thread for installing a Holley carb metering jet of any size. In other words, you can then change the size of the 3rd feed hole without removing the valve body and changing the separator plate.

I'm glad Jake is helping because this is beyond my experience level.

 

What you have to remember about this circuit is that the 3rd feed hole sizing in the plate feeds to BOTH the 3-4 clutches and the backside (inside, disengage side) of the 2nd servo.
So drilling the hole bigger will bring on the and 3-4 clutches quicker AND kick the band off quicker.
If you just drill the hole bigger it should kick both off faster and timing should stay close BUT,
the size of the servo, the strength of the servo return spring, the clearance of the servo,and the clearance in the 3-4 clutch pack all affect it.

 

Since I suspect you want to learn more about how the hydraulic circuits work, you can read the detail in GM's 4L60E Technicians Guide. You can view/download it online here:

http://www.grail-ss.com/GRAIL%20Webs...ETechGuide.pdf

You might just need a stronger servo return spring as Jake suggested.

 

I woke up thinking about it. I solve most of my mechanical or technical problems first thing in the morning. I have come to the same conclusion. I think the route of the problem are the transgo high rev springs. I used them all against the advice of some builders on here. I don't think the servo spring is keeping up. I've heard there is a much stiffer spring used in the 700r4 or something. Is that just stock? How can i find the right one?

Ted, thank you for the guide. I do want to understand the workings of these transmissions and I'll read it thoroughly.

Edit: My logic doesn't hold up for the 3-4 clutch springs to be the problem. Since the 3-4 clutch is engaging while the servo is releasing on the same hydraulic circuit, the heavy 3-4 springs should help to slow the engagement of the 3-4 clutch. Anyway, a heavier spring should still help create a faster servo release so that's the first thing I'll try. Plus it's the easiest and least expensive thing to try if I can figure out which spring to get. If I remember correctly, the one I put in there was red.

 

Some builders don't recommend the stiff cage strings and I have documented that I only use half of them. In the 3/4 return cage I use just 14 of them.
In the forward/overrun return cage I alternate Transgo and stock springs.
I have built, driven and raced three transmissions like this and all have worked well with shifts at 7000 rpm. (Or a bit more.)
I estimated the stiffness of the Transgo springs (3x stock!) and aimed for
a 50% to 100% stiffer spring cage, not 200% stiffer.

I would first try a stiffer servo return spring, assuming you can get the servo out without removing the trans.

 

I think I can, it's in the Tahoe. It was easy with the stock servo. Maybe the super hold 4th won't be too big to get out. On my next build I'll probably just use the stock 3-4 springs and new springs in those little boost spring assemblies.

 

Thinking about it more, I propose that stiffer cage springs are more likely to cause a flare, not a bind....

One hydraulic detail that surprises a lot of people is that when the 3rd apply circuit is pressurized, the 2nd apply circuit stays pressurized. The only reason the band releases is that the surface area on the inside of the 2nd servo piston (where the 3rd apply fluid goes) is larger than the outside (where the 2nd apply fluid goes). Now the inside surface area is the same for all pistons, but as you go from the stock, to the Vette and then to a Billet 2nd servo piston, the outside area increases in order to put more pressure on the band. However that means the 3rd apply circuit will need more force to disengage the band. I'm not sure how important an issue this is, but I think GM even drills the 3rd feed hole a bit bigger when the Vette servo is used. (Shift kits tend to drill it much bigger yet.)

Think of a cylinder with two pistons on opposite ends, each with a different strength spring pushing the piston into the middle. The way I see it, one piston represents the 2nd servo piston, the other represents the 3/4 clutch piston and the 3rd apply circuit goes between the pistons. As the pressure between the pistons increases, the one with the softer spring will tend to move first. Depending upon which moves first, you will have a flare, a bind or a perfect shift. Since perfection is to difficult achieve, one way around it is to increase the fluid volume very quickly (bigger feed hole and/or more pressure) so that any minor flare/bind is too short to be noticeable.

Therefore my hypothesis (unproved theory) is that stiffer 3/4 cage springs are more likely to cause a flare because the 2nd servo piston will move (disengage the band) before the 3/4 piston moves to engage the clutch.

I probably have some details wrong here, but this might help explain why any mods to the stock setup have to be "balanced" to work correctly.

 

If you have a tie-up on the medium throttle 2-3 shift, You will have the sensation of going forward when this happens. When using the Sonnax 2nd apply servo drill the band release hole the separator plate to .104" and the 3rd feed hole to .120" - .135". This should fix the tie-up problem, if that is what you have here. Plus remove the Sonnax servo check valve, to eliminate any possible problem with it. I do not use or like the Sonnax servo check valve, and I concur with Jake on this. I always install all the TransGo clutch return springs on everything that I have built for the last 20+ years without any problems. I have been using them in my rebuild kits without any problems when using the .471", .490" or .500" boost valves. It only takes an additional 5 pounds of oil pressure to overcome the additional spring pressure. I setup the 3-4 clutch clearance to .020" - .035" when using the #7 apply ring (stock in 4L60E's). If you use the #4 apply ring (stock in 700R4's), then you must run more clutch clearance (.040" - .055") or you will have a tie-up. The same goes for the 700R4. There are more things that can be done, but this should suffice here.

 

That sounds good. I am not sure which apply ring i have but i must assume its the #7 because its a 4l60e and i didn't replace it (i will for all future builds). My clearances are exactly what you listed. I'll drop my pan this week or next and set those feed holes to your spec, remove the check valve and go. I've heard of builders dropping valve bodies to perfect a shift so um not surprised our disappointed that its what i need to do.

 

Glad that Dana (PBA) has experience with both the Transgo springs and the Sonnax servo pistons and can therefore give you good advice.

Dana, what is the "band release hole in the separator plate" that you refer to?
Looking at the hydraulic circuit on page 56B of the Technician's Guide, the only restriction I see for the 2nd apply/release is #16 (the 2nd feed hole) and it has a checkball for fast release. Are you saying to drill the 2nd feel hole to .104, a bit bigger than the .093 recommended in the HD2 kit?
Thanks.

 

Ah, i didn't know that was Dana. Great! I have learned a lot from this build and I know that there is a lot to learn yet. I have looked extensively at Dana's kits and will certainly be buying one for my next build. I think they're well thought out with just the right components. there are a few details about them that make them superior to most of the others I've found.

 

Here's what I think I need to do. Can anyone verify that the holes I marked are in fact the ones I need to modify?

 

At the top of the separator plate circled in red is the band release hole. I recommend .104" here with the Sonnax 2nd apply servo. The feed hole circled in red in the middle of the separator plate, is the 3rd feed apply hole. With a 4WD, drill this to .120" maximum. The one circled in red to the left, is the 2nd feed apply hole. With the stock diameter torque converter, drill to .076" - .082" maximum. With the Circle D 11" diameter torque converter, drill to .086" - .093" maximum. The one circled in black just below the 2nd feed apply is the 4th feed apply. Drill this to .093" - .104". If you are going to make 3-4 WOT shifts, then drill it to .120". Do not forget to follow the instructions from TransGo for the other feed holes on the separator plate, as they are necessary.

 

In that picture the top hole is circled in black. Is that what you meant?

 

I was wondering the same thing.