Typical no 3-4, began teardown. To remove the servo I had to clamp vise grips onto the cover numb and hammer it off. The cover had separated from the case and the oring was visible but still wouldnt release. Now apart I'm not seeing much that would have caused that to stick. Also the band/drum are showing signs of heat. And then of course 3-4 clutches are burnt. Strange, usually these pop right out.

 

Did you cut the blue servo cover o-ring when first visible and then pull it out?



Yes, I have vice grips on it, but it then comes off very easily.

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Have you decided what frictions and steels to use the for the 3-4 clutch yet?
How many and what did you have in there before?

May I suggest:

.215 Apply
8x .067 Friction (BW Hi-Energy or Raybestos GPZ105)
7x .078 Kolene steel (TranStar part #74120AK)
.157 Backing
.092 Snap ring (stock)

==> .038 to 0.040 dry clearance

This was discussed in this thread:
https://ls1tech.com/forums/automatic...some-info.html

PBA suggested a slightly different combination.
I would really like to know what you had that failed.

 

The oring was out past the housing, that wasnt what was holding it. And it wasnt any normal force to get it out, repeated hammering(on my grips) finally popped. Now disassembled I cant find anything that would have caused it.

Reading all the posts here I'm not sure where to go on 3-4 clutches, z-pack, ac delco 4l65e upgrade???

I have 6 frictions currently, they burned up in about 20,000mi. Wondering if its a pressure problem. The previous rebuild wasn't by me. The release springs were also still installed on the 3-4 also.

 

I would avoid the Z-Pack; I'm pretty sure none of the sponsors use that any more. The AC Delco 4l65e upgrade is fine; it consists of 7 BW .067 frictions and 6 .095 coated steels (about $60 at the dealer). However most performance builders are now using 8 frictions as I listed above or slight variation.

And yes, adding a shift kit to increase pressure and volume to the clutch will help regardless of what frictions you have.

 

This is good tested and tried info, think I'll go with your set-up and a shift kit, I dont see my front left wheel lifting anytime soon. Thanks!

 

Update..applied 50psi of air to 3-4 pack, its leaking somewhere, takes 30 or so to over come the leak and move the piston. The other packs hold the air and it releases only when I remove the blowgun. I was hoping to find an issue and not have to guess

 

Sounds like you already have the trans apart and are testing the input drum...

Remember that the 3-4 clutch has a bleed hole in the input drum which will always give it a bit of a leak unless you cover it with your finger. There is also a second bleed hole with a check-ball - the HD2 kit recommends replacing that with its supplied simple bleed hole; you then have two holes to cover for an air test.

 

As you mentioned I think the leakdown is normal...thought I struck gold.

However, I just read a gm service bulletin that mentions a servo malfunction can cause the 3-4 to fail. Since mine definately had some kind of issue when removing I should take a closer look at that tonight, the orings looked fine but I only took a quick look. The band wasn't worn out but had signs of slipping heat and the 3-4 clutch wasnt completely burnt 2-3 friction down to metal, the others looked fine. Heres a caption of the tsb1572774

2-4 Servo Piston Seals for being cut or damaged

2-4 Servo Apply Pin for being nicked/scored /binding in the pin bore

2-4 Servo Piston Bore for being scored or mismachined

 

Not trying to derail the thread but I'm just curious, why do you say no Z-Pack? The trans builder at my dad's work rebuilt my trans 30K miles ago and I had him install the Z-Pack.

This is in my Silverado but it has been perfect since and I've towed quite a bit with it.

 

The 3-4 clutch is marginal at best and any leak in the apply circuit results in rapid failure.
The servo actually acts as the 3rd accumulator to soften the apply; a leak in the servo will result in failure. Sonnax makes a servo seal kit 77701-04SK which replaces the stock cut-rings with much tighter fitting o-rings which probably also compensate better for any wear.
In the same area is the 3rd accumulator checkball capsule which is pressed into the case. It seems a lot of hasty/newbie builders overlook this, but if it leaks the 3-4 clutch will fail. The 3-4 circuit can also leak between the pump halves.
With so many potential leak points, IMHO, I suggest drilling the 3rd feed hole in the separator plate bigger; this gives the circuit more fluid to overcome a few tiny leaks. The Transgo HD2 kit recommends drilling it to .093 or .101. I know some performance builders drill as big as .125. Some install the Sonnax servo release Check valve (77701-076) which then recommends drilling to around .125.

The clearance in the 3-4 clutch is also moderately important. Instead of thinking overall clearance, you should think clearance per friction. From what I have been told the suggested clearance per friction are:
Hi-Energy (Brown) - .003 to .007 per friction (wet)
Performance (Red) - .004 to .007 per friction
Super-HP Blue - .005 to .008 per friction

Therefore, while the total clearance with 7 Hi-Energy friction might be as low as .025, with 8 Blue frictions the total clearance should be around .050. The Blue frictions are soft and sticky and you don't want them wearing on the steels when the clutch is NOT applied.

lt1pwr1: I regularly talk to various performance builders and my impression is that the Z-Pack was the hot ticket 10 years ago, but better options are now available, especially for engines over 400HP. It is rumored that Raybestos may discontinue the Z-Pack due to low demand and is suggesting the GPZ-100 or Blue frictions in its place. In short - nothing wrong with it and don't be concerned that you have it; there just seem to be better alternatives now.

Again, I'm not an expert, but I experiment a lot myself and frequently talk to the experts.

 

I bought the superior kit with boost valve which also recommends drilling the plate, that will be a for sure. I'm going to order the check valve now. Thanks mrvedit

 

assembled input drum, applied air to 3-4 and found a leak where the input shaft meets the drum, theres no fix I can find for this. Looks like a new drum is needed

 

Bummer. The input shaft is pressed into the drum, but I suspect that won't help you because the aluminum around the shaft has stretched a bit.
Sonnax sells new input drum/shaft combos with heat treated input shafts (like the 4L65E). I'm not sure of the part number, but I could ask a Sonnax expert (CarsonAuto) to chime in here.
Otherwise, check ebay. I have repeatedly been very happy with ebay seller "powertrainpartsplus" and they currently have several input drum/shafts for sale for $40. A local trans shop might even have some spares to sell.

 

I have a long time Chevy dealer connection who got the superceded input for $106. Also had to order a thicker 3-4 pressure plate to get the clearence you suggested $5. And I'll have them tomorrow. 3-6 inches of snow Friday=garage time. Next..DY teflon ring fitting.

 

Good price for a new input drum/shaft. Going 7 or 8 frictions? BW HiEnergy?

Sucky weather in MI too. I have a 4150-style intake manifold with throttle-body EFI. Hope to port the intake this weekend to match my CNC ported heads.

 

7 B&W, I had .060 3-4 dry clearance, the new plate is going to be too tight I think. TB efi is it holley projection?

 

Should be OK to tighten that down to .040 or even a bit less if needed.

I had a Holley 950 Multiport system on my old SBC 383. Incredibly, the TB from that system worked fine with my 2002 PCM; I guess it had a GM compatible TPS, MAP and Idle-controller. All in my '81 Camaro with raised hood so that I can put a stock-looking air cleaner on top. This configuration is at least .2 ET faster than my original LS6 intake with a cold-air box. Fun to show off at the track because even the gear-heads cannot figure out what the engine is.

 

Anyone know where I can buy a 3-4 retaining ring thicker than .093"?

 

Don't think there is a thicker retaining ring.
The better way is get a few thicker BW HiEnergy frictions and mix those in with different apply plates to get the clearance you want. BW HiEnergy come in .067 and .096 thickness, perhaps even .080. A local trans shop can get them for you by tomorrow.

 

So I assembled 3-4 in the new drum with .060 dry clearence, once the plates were soaked in atf there was little to no clearence. I had to use alot of force to turn the fiber plates by hand...normal?