Modded 4L65E question/issue - trans guru's in here
 

Hey guys, I am posting this for someone. Also im posting this on tech rather than PT.net as I think it will get more attention on here.

Last year I sold my modded Silverado SS with a built tranny that I built. Its having a slight issue as of lately the new owner claims that kinda has me stumped and wanted to run this by the trans guru's.

When I first built the unit I was having issue keeping forward sprags. I went through two then I decided to try the 2-3 shift valve mod to apply the overruns in the manual gears to help support the sprag. This seemed to work very well as I know the new owner hasnt been easy on it so far. He now has an issue when its in D (overdrive) and goes to shift into 2nd it is like it goes into nuetral and will stay there untill you actually put it in nuetral or manual 3rd then back to D it will then engage low gear but go back to "nuetral" again when going into 2nd. It does this everytime in D but it does apply 2nd in all manual gears like normal. I had him drop the pan just to check it and he said the fluid is clear as a bell. Also had him check for any DTC's and none found.

This has me puzzled. I want to point at a shift valve as like he said when you move it to nuetral or 3rd out of D, then back in D it engages low gear. Or could it be an o-ring on the pressure manifold?

Look forward to some responses

Below is a list of the parts I built it with

Corvette intermediate servo
Sonnax billet overdrive servo
Double cage 29 element forward sprag
Low/Reverse spring roller
Alto red low/reverse clutches and Koleen steels
Alto carbon oversized 2/4 power band w/ reinforced anchor
New input drum/housing
Borg Warner High Energy Green 3/4 clutches and Koleen steels
Rebestos blue overrun clutches and Koleen steels
Beast reaction shell
New reaction sun gear
GM rear 5 planetary gear set
Rear carrier ring gear
Thrust bearing kit
New upgraded babbot pump bushing
New case bushing
New extra wide sun gear bushing
Sonnax boost valve
Billet forward accumulator
Billet 1-2 accumulator
EPC Solenoid
Superier valve body shift correction kit
4L65-E overhaul kit(gaskets,seals, ect)
Updated valve body seperator plate
Billet 300m output shaft
Billet 300m input shaft
Billet input drum sleeve & piston
RPM high-rev spring kit
Modified case

Looks like a very well built transmission; even with billet input and output shafts.
You obviously know the 4L60E very well.

Do you have the "GM Hydramatic 4L60E Technician's Guide" ?
It diagrams and explains all of the hydraulic circuits. Figuring out if a valve is sticking the valve body is beyond my experience level. If you have the guide you might check if there is a difference in the 2nd servo piston apply depending upon the position of the shifter; it seems that the D4 circuit is shutting something down. Your thought about the pressure manifold certainly is reasonable and would be quick and inexpensive to replace. Trying a rebuilt valve body might be the next step, or even just putting on old used one to see if that solves this problem.

I dont consider myself a "guru" by any means but I have been through my share and consider myself to setup a decent trans.

I do not have the guide but would be usefull. Im just having him start at the valves because it makes sense as to what it does when you either go to manual 3rd or neutral it engages low and everything works ok in manual 3rd. Which tells me moving the valves around does something. But again, I have only looked at my chart that shows what is holding/applied but that doesnt tell much for this.

I guess a shift valve hanging or a bore issue in the VB will or will not trip a DTC? I have seen an issue with a valve/bore issue before on an Allison trans and would only do it when hot and put it in limp mode naturally. But this one is free wheeling which it throwing me off.

Here is an online version of the guide:

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

If it were me, I would just test another valve body, but then I have extra ones. If you want to try that route, tell me what year the PCM is.
However, I would first replace the pressure manifold; someone else here had very strange symptoms and that cured it.

Wow that guide is kick ass. Def going to save that.

I think trying another VB would be ideal but it would of to be modified for the 2-3 shift valve mod.

I don't know how "crazy" this problem is driving you, but I was thinking just an old valve body to quickly test if it solves the problem. I know it takes a good hour or so to change valve bodies. And I know that the 2-3 shift valve requires a non-reversible mod.

In case you consider this and don't have access to a spare VB, I have bought several from ebay seller "powertrainpartsplus". I have bought both very good ones ($90) and as-is ones ($30) for experimentation. I wouldn't put a $30 one on permanently, but it might be enough for a test to help isolate the problem.

I agree.

He said he can get a VB from a friend he knows. With that said im going to have him pull the VB out and remove the 1-2 shift valve and inspect it and the bore. Also the spacer plate even though it is the updated one you never know. Depending on what he finds here will depend on if repair will be made or a test VB will be put on

I will keep ya'll updated. Thank you for your interest in this and the awesome guide

Well the test VB didnt work

With that said, I called him and got some more info out of him. He said now it will not move in D or manual 3rd. It will move in manual 1st and manual 2nd and will up shift if you manually shift the gears. I asked him why is it a different story than before? He said he must of not tested enough then like he did now. I guess thats what happens when you are working on a trans clear across the country.

Anyway, with that said I am condemning the forward sprag. This will be the 3rd sprag I have been through in this thing. First time I rolled the sprag I reused the race. Second time I relaced the race and sun gear assembly. And third its obviously not apart to see. I figured it would last a little longer with the HD sprag and the 2-3 shift valve mod to help support the sprag. I guess at the end of the day its still a 4L60, in a heavy truck, making too much power.

On the other hand, I talked to him about telling his customer to convert to an 80. He agrees and is going to talk it over with him. I would like to make a deal on that trans for my Camaro project. Get it back, take it down, repair what is broke, swap output shafts, throw in a fresh set of 3/4's, and roll with it.

Bummer. I understand your aggravation in trying to solve a problem based on "symptoms" and then having the customer change the symptoms.

With the 2-3 HD valve installed, it should keep the overrun clutches applied in D3. I suspect the customer isn't reporting it quite right, or the overrun clutches are getting worn out.

Blue frictions are available for the overrun clutch (Transgo R74116HP) which might help a little for your next rebuild. IIRC, I have heard there is an extra-wide dual-cage sprag that will fit, but haven't seen one myself.

Curious - about how much power and weight does the truck have?

The unit already has the blue overruns with koleen steels. And all three sprags have been the double cage 29 element

The truck weighs everybit of 5500 lbs, AWD, factory heavy wheels, D1SC blower with 13-15lbs of boost and a 3600 stall converter.

So I am not sure if he had it in manual 3 when he was hot rodding it or he had it in D. We'll never know it.

IMO your overun clutches are wiped out and a foward sprag issue.

Only know if the overs are gone when disassembled

Sounds like the sprag is out again. What are the feed sizes in the plate?

I dont remember off hand and I would have to find where that info is. Plus the trans is in Florida so I cant physically check them. Are you thinking something is getting starved?

I am curious too why/how feed sizes could affect the sprag. It sounds like the overrun clutch actually is/was holding pretty well.

Also, I've been researching the existence of an extra-wide sprag. Even bought a new 4L70E sprag assembly for detailed research, but it was not extra-wide. So, I re-opened this old thread on the subject:

https://ls1tech.com/forums/automatic...ent-sprag.html

Well he got it apart and wow....iv never seen a sprag explode like this

http://i3.photobucket.com/albums/y95...psfba2fd08.jpg

Like mentioned above, this is the 3rd sprag that has failed BUT the first two times the overruns were not supporting the sprag and I cant prove they were this time either

The fact that he could drive at all in D3 indicates the overruns were well engaged.
I've never seen a suggestion to drill the overrun feed hole bigger, but don't see how a slighter bigger hole would hurt.

Was that a BW dual cage sprag?
IMHO the entire sprag assembly should be replaced after a failure like that.
Part # 24241477 on Amazon for $160.

Yes it was the BW dual cage sprag. And I agree on the entire sprag assembly needing replaced. After the first failure, I replaced the sprag assembly as I thought with it being used it was worn enough where the sprags werent going to hold. Well that didnt matter obviously lol

BUT, I keep saying this but I cant say he was in manual 3rd when this happend either

Thats not a dual cage sprag. Looks like a single cage SKF IMO.

That's what I was thinking too. I don't see in the inner case unless it completely disintegrated.