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Discussion Starter · #1 ·
Self built 4L60E has survived 30K+ miles street
and lots of 12's at the 1/4
and many trophies at the autocross
over 4 years now.

4L60E Build:
Edge 3500 stall converter
Alto Red clutch's
trans go HD2 fully installed
trans go Vacuum Modulator w/ nice line rise over diminishing vacuum
110PSI idle
260+PSI WOT
BW 29 element sprag
sonnax .500 boost valve
lots of spacer plate drilling
and various other tweaks.
external filtration and 3x coolers!


This weekend post autocross I got some nasty symptoms.

Fist sign of trouble
violently gave up 4th for a 100% slip neutral then back to 4th.
at around 12% TPS but thats a decent amount of power in this ride.

played with it in the parking lot.
-reverse is good
-manual 1 *is good
-manual 2 * is good
-Drive *no forward movement from a stop
-Overdrive *no forward movement from a stop
-Drive and OD *a friend could push me and it would temperately pop into gear then back out

on the street.
1st and 2nd are rock solid
1 > 2 shift is firm and positive
If I pumped the 4L60E out to 60 MPH in 2nd then popped it into 3rd or Over Drive.
All gears were present with lock up.

Drive and OD are sometimes present from a stop

I'm thinking the BW 29 element dual cage sprag gave up the good fight?
If that failed how do I make it live next time?

Tear down soon.
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Discussion Starter · #2 ·
nobody want to take a swing at this one?
 

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I'm with you - Sprag is rolled over and is only gripping intermittently. The violence you felt in 4th was the sprag rolling over and temporarily binding. If you have a fully binding sprag, 4th gear will bind. Same thing as if the overrun clutches are on all the time like when the forward piston cracks and leaks pressure into the overrun piston.

FWIW, I've experienced broken sprags that would still grip enough to give 1st and 2nd gear in OD under light throttle but would slip with anything more than that. Putting it in D, 2 or 1 activates the overrun clutches which mask the broken sprag problem.
 

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Discussion Starter · #4 ·
FWIW, I've experienced broken sprags that would still grip enough to give 1st and 2nd gear in OD under light throttle but would slip with anything more than that. Putting it in D, 2 or 1 activates the overrun clutches which mask the broken sprag problem.
Thanks,

That sure feels like whats happening.:(
 

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Discussion Starter · #5 ·
But what do I do about the sprag?

What is the strongest part?
Is there any supporting mods?
 

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Replace the whole sprag assembly, first off. There was at least one GM sprag housing redesign according to the ATSG 4L60E update manual. Beyond that, it's beyond my experience. I would talk to a well-regarded builder about sprag failures, like Dana at ProBuilt or Shane Cobb; maybe PATC or Finish Line Transmissions and see what they say.

Or you could have just ended up with one of those statistical oddities where yours failed for no good reason. :p
 

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Discussion Starter · #8 ·
Roger that tower
 

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There have been a lot of failures with late model input sprags on newer ’07 – ’08 vehicles and some design changes. I heard recently of a plastic cage design. At this point I am not sure which one is failing but I do have some preferences I will share. The key to making a sprag live is keeping the inner and outer race concentric. Once they are off center from each other the life is short. For this automotive application it is the sprag end caps that keep the two races concentric. Of the more common 4L60E designs there was the SKF with stamped (rounded) end caps and the BW with machined (squared off) end caps ( I think I have the names correct). Anyway, I prefer the style wiith machined (squared off) end caps as I feel this gives better support to the races and keeps them on center with each other. Also, you may want to consider the Sonnax 2-3 shift valve 77754-41. This brings the over run clutch on in D3 (1st & 2nd ) gears will add durability top the input sprag, forward and over run clutches. I D3 it makes the 4L60E work like the older 700-R4.

Hope this helps,
Gregg Nader
Sonnax Tech
 

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Discussion Starter · #10 ·
WOW WOW WOW

cool Greg thanks for the great post.

This part will increase my fuel economy around town by allowing my Decel Fuel Cut off to engage.
As it will not normally engage the PCM DFCO w/o good vacuum aka heavy MAP signal when using a high stall converter.

With this part
the sprag has Overun support at the drags, around town and high and low speed autocross.
everwere but the freeway were the loads are light on the sprag.

http://www.sonnax.com/announcements/77754-41.pdf



You got any clever tricks to run a more clutchs and steels in the over runs?


any other cool Sonnax parts I need to know about?
 

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I prefer running high energy in the o-run, but have not been able to find them new, only good used. I believe GM went across the board with HE then backed off and went back to paper in the non-shifting clutches to save money. I have devised a way to potentially get 50% more friction into the o-run, but this would require some expensive custom clutches and I have just not heard that many looking for it.

As for other stuff for the 4L60E, we have a lot, just check the performance section of the Sonnax website. All 4L60E parts are categorized into valve body, pump, servo, other/internal etc. making finding parts easier than before. More new stuff is on the way too. Notable parts are a Teflon rear stator bushing, input housing reinforcement sleeve and a billet aluminum forward piston.

Gregg
 

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Discussion Starter · #13 ·
I have devised a way to potentially get 50% more friction into the o-run, but this would require some expensive custom clutches and I have just not heard that many looking for it.
Ok drop it on me!

How about machining the parts so more stock type clutches fit.
 

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Gregg, what's wrong with the stamped steel forward piston set that you made a billet forward piston?

The Sonnax input housing reinforcement sleeve can only be used with an aluminum o-run piston. Aluminum o-run piston should only be used with aluminum forward, not stamped steel. OE aluminum forward breaks, thus our billet forward brings max durability.

Gregg
 

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The Sonnax input housing reinforcement sleeve can only be used with an aluminum o-run piston. Aluminum o-run piston should only be used with aluminum forward, not stamped steel. OE aluminum forward breaks, thus our billet forward brings max durability.

Gregg

I have actually used a steel forward piston with an aluminum overrun many times. You just have to know how to do it.

If the overrun comes on by itself it will blow the seal. But in practice that never happens :)

I have done this probably 15 times all working well. Once again things that shouldent work do.


Tad, I would purchase a new sprag housing and install another BW dual cage sprag. THose units hold up in 800 hp cars and are very strong. You just have a fluke there.

When your racing you can keep it in drive if you want. THat will take a few PSI off the main line going to the 3/4 clutch but it wil keep the overruns on and will effectively support the sprag.

Get rid of the alto commercial clutches and go with the raybestos Blue plate frictions. The thin ones.

You can fit 10 in there with the thin steels and thin frictions. Dont let them get hot and they wont warp. Set clearance to .015.
 

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Discussion Starter · #16 ·
Get rid of the alto commercial clutches and go with the raybestos Blue plate frictions. The thin ones.

You can fit 10 in there with the thin steels and thin frictions. Dont let them get hot and they wont warp. Set clearance to .015.
I only use the commercials in the 3/4
the 3/4 a 9 pack.
Alto Reds for the forward apply and 2/4 band
everything else is BW high energy
many 12 second passes and many years and many miles later
I have never burnt a clutch pack up.
works for me.

I keep um tight run the vacmod that non one likes but me and I lightly score my steels.
again it works for me.

I have actually used a steel forward piston with an aluminum overrun many times. You just have to know how to do it.

If the overrun comes on by itself it will blow the seal. But in practice that never happens :)

I have done this probably 15 times all working well. Once again things that shouldent work do.
What is the benifit of the steel forward with alum piston?

Even broken the 1 and 2 work without the sprag.
works great.!
Drove home 140 miles like that....:confused:
Your saying the over run seal should have blown?

I
Tad, I would purchase a new sprag housing and install another BW dual cage sprag. THose units hold up in 800 hp cars and are very strong. You just have a fluke there.
I think thats what I'll do.
Was considering TiGing the slip out of the sprag carrier....???:confused:

When your racing you can keep it in drive if you want. THat will take a few PSI off the main line going to the 3/4 clutch but it wil keep the overruns on and will effectively support the sprag.
I use 1 & 2 in the burn out box
and Drive down the 1/4
...is that cool...

on the autocross I use 1 to leave the line
and 2 the 90% of the time
sometimes I will manual down to 1 then right back up to 2
so only 1 & 2
..that has always served me well..
no radical 4 upshifts with a nasty 4-2 or 4-1 down shift.
just lock it in and go.

The failure a fluke.
That sprag has hung in there a long time.
I leaned on it in OD being sporty on the street with new parts and it broke.
After many miles and combos infront and bein d the trans.

new 3500+stall edge, new 335 Kumho710 slicks, and custom Tri-Y long tubes w/ 3" exhaust and the sprag just didn't hang in there.
http://www.impalassforum.com/vBulletin/showthread.php?t=232659




or it could be a fluke...

I did kill a Raybestos Mechanical diode / sprag at 290RWHP a long time ago.....???
Seems like that was post autocross on the freeway at 75MPH?

BTW have you ever got more than 2 frictions in the OVERRUN pack?
 

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Why would you put more overrun clutches in? I know they will wear out quickly if you try to downshift without giving throttle, but is there a time you need this?
 

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Discussion Starter · #18 ·

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Discussion Starter · #20 ·
So you're autocrossing in the stock seats? How do you manage to stay planted?
I just put in M5 Ricaros.

int that video
I have my left leg slamed in between the door and the seat!cwm5
:Dcwm5
 
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