maxspeed05V

iTrader: (4)

4l70e in a 06 ls2 trailblazer ss with bolt ons and a cam .

trans was built about 3 months ago by a local shop. He used the kit from 4l60e.com, vette servos mild shift kit etc. Nothing to special but built better then OEM

Also installed was a new circle D 3200 single disk converter


Heres the scoop :

I was on the highway playing a little cat and mouse on the freeway with a 5th gen camaro , nothing to wild . ( ya I know not smart doing roll runs in a 5000 lb tank )

Then as I got off the highway the truck felt very funny, it almost felt like the ebrake was on or someone attached a 5000lb trailer , truck was struggling .

I limped it home the next mile.

The next morning I went out for a ride hoping all would be good, but no 3rd gear. I have a vid I might load up later, but it shifts first to second nicely but as it tries to shift into 3rd the motor just revs.

I dropped the truck off at the builders since the trans is still under warranty . They will be taking it apart next week.

wtf happened that made the truck feel like the brakes were on or like I was towing a trailer.

And my big question, is my converter f*cked ? Could that have cause any issues to begin with ?

I'm just looking for any input, I trust my trans builder but I also want to be as educated as possible on the subject.

Jake's Performance

iTrader: (2)

Possibly a forward sprag failure.

mrvedit

Sounds like the notorious 3/4 clutch problem which is the weakest part of a 4L60E (a 4L70E is a 4L60E with Input Speed Sensor).

Make sure the shop this time uses 7 or 8 frictions for the 3/4 clutch, preferably Borg Warner High Energy or Raybestos GPZ100/GPZ105. Don't put a Z-Pak into a heavy vehicle.
If you can afford an extra $650, have them use the Sonnax Input Drum with 9 frictions.

Depending upon how much friction crap there in the fluid, the converter may need to be sent out for opening and cleaning.

maxspeed05V

iTrader: (4)

Ya 3rd is completely toast , wont engage at all so I assume there will be a lot of crap in there . Can it be flushed out manually in the truck once its together or does the converter need to be taken apart to do it ?


What about 1/2 clutches ? should I have them swap those again aswell ? Or will he be able to tell once its opened up ?


One other thing I'm unsure of is I left about %50 tq management in the tune. I assumed I was doing a good thing, but could that have contributed to the damage?
TQ management is such a gray area it seems and everyone has a different opinion

mrvedit

I don't have the experience to answer your question about cleaning out the converter.

1st gear has a clutch and it generally holds up very well.
2nd gear uses a band to engage and it hold up fairly well, better with the Vette servo.
3rd gear uses the 3/4 clutch inside the input drum and it is a weak spot.

The default 6 frictions in the 3/4 clutch are insufficient for any performance upgrades. The 4L65E and 4L75E came stock with 7 frictions are an improvement.

I don't now what "mild" shift kit was installed, but you will want:
1. Better quality 7 or 8 frictions as I listed above.
2. Keep the 3/4 clutch clearance well under .050, .030 to .040 is good.
3. Drill the 3rd apply hole to at least .100.
4. Install a .500 boost valve if not already from the shift kit.

MOST IMPORTANT - The builder needs to be sure there are no leaks in the 3/4 hydraulic circuit.

There are other tricks to improve pressure during high RPM operation, but a bit much for a quick post.

The torque management lets your trans and frictions live longer, so yes a good thing.

If quality frictions and a reasonable shift kit were installed, considering the short 3 month life, I suspect there was a leak in the 3/4 clutch circuit due to a "quicky" rebuild.

maxspeed05V

iTrader: (4)

To be completely honestly I forget now which clutches he used but I'll ask him again . I've been around ls motors for years but autos are new and Greek to me .
He's done a few trans builds on some fbodies I know and the cars are making big power an run like hell . So he's done good work and I trust the guy .
Is doing a transmission for a truck much different ?



Also , I've been told keeping it in 3 is better for the trans when going wot then D .
Is this information correct ?

mrvedit

A truck is mostly identical (I would install billet 2nd and 4th gear servos). I posted several 3/4 clutch combinations that members here have followed successfully. A local trans shop has been using my combination for their performance builds, and it has stood up well in heavy 500+ HP pickup trucks. See my post #2:
https://ls1tech.com/forums/automatic...some-info.html

That unfortunately is wrong!
Unless your trans was built with the Sonnax HD 2-3 shift valve.
(I think it was right for a 700R4, but not for a 4L60E).

Part of the confusion is due to an error in the ATSG manual. I point this out and get confirmation in this old thread:
https://ls1tech.com/forums/automatic...-drive-od.html

Note Jake's comment about the the Sonnax shift valve in post #14:
"The Sonnax piece is an almost mandatory upgrade IMO."

In short, when in [D3], during the 2-3 shift the overrun clutches are also applied and this diverts some fluid/pressure from the 3/4 clutch.
I will add that by increasing the size of the 3rd feed hole, installing a bigger boost valve and other tweaks, that a performance built trans can engage both the overrun clutch and the 3/4 clutch at the same time without problems, but why risk it. Unless you have the Sonnax valve installed, race in [OD].

If possible, find out what the builder installed, post it here and we can evaluate it.

maxspeed05V

iTrader: (4)

Thanks for all the info

maxspeed05V

iTrader: (4)

What was the deal with the truck feeling like the ebrake was on when I finished the spirited driving ?

mrvedit

That typically indicates that the trans is trying to engage 2nd (band) or 3th (3/4 clutch) while in 1st gear. The answer probably won't be known until the trans is rebuilt. We've had a few recent threads where the input drum failed and the frictions inside got all jammed up.

maxspeed05V

iTrader: (4)

red eagle 3-4 pack was used . He named a lot of the other things but the 3-4 I remembered .

Circle-D_Brian

I would go ahead and send the converter in for a cut and clean. Feel free to give us a call or an Ask Chris email, and we can get you helped out. It would be a shame to hurt a new transmission with a fouled converter.

-Brian
713-895-8834

mrvedit

IMO, the Red Eagle 3-4 pack is a poor choice, especially for a truck, as it consists of many super thin frictions. There is always heat build up (especially in a truck) and this warps the frictions. The frictions are also vulnerable to coning due to the (poor) design of the stock input drum. I am not aware of a single pro builder on this forum still using them. (Some tried them 5+ years ago with poor results.)

Obviously you need a rebuild and it is a good idea to send the converter back to CircleD for a cleaning.

I have documented a 7 and 8 friction setup based on discussions with pro builder here and my own experimentation. There is no consensus on whether 7 or 8 is better, but both have held up well even in trucks. See post #2:
https://ls1tech.com/forums/automatic...some-info.html

Or if the budget allows, get the Sonnax input drum and put in 8 or 9 quality frictions. Pro builder here have tested this at 750HP in pickup trucks.

maxspeed05V

iTrader: (4)

What's this going to cost me ?

Will they know once they pull the trans if it needs to be cleaned ? Or does it just have to be done ?

mrvedit

Dropping the pan to see how much friction material is in it might help determine if the converter needs to be sent back. If there are any metal fragments it absolutely needs to be sent back. If you do it, post a picture and hopefully one of the pros can then answer that question.

Your "feeling like the brake is on" is not the typical symptom of a burnt out 3/4 clutch. We had a recent thread where the snap ring tabs in the input drum tore off; that would give you loss of 3/4 and other symptoms.

If/when the trans is rebuilt, I would appreciate seeing pictures of the "carnage" for my own educational feedback.

Jake's Performance

iTrader: (2)

Feeling like the brake is on sounds like a failed forward sprag, which would cause 3-4 clutch failure...

mrvedit

Thanks. Now I understand how your earlier post about a failed forward sprag fits in.

Jake's Performance

iTrader: (2)

Sprag fails, then it can't overrun in 4th, so the 3-4 clutches get taken out immediately. Possibly all caused by a downshift.

maxspeed05V

iTrader: (4)

That sounds like what happened , because I was on the highway doing my spirited driving and the downshift in the tbss is rough . I shouldn't have done it , these trucks are to heavy for roll racing .....

But wouldn't it kill the 1-2 shift and clutches as well?

Jake's Performance

iTrader: (2)

No it won't affect the 2nd band. The forward sprag overruns (freewheels) only in OD. So when it fails, depending on the failure mode, it will lock up and kill the 3-4.