700R4 2nd to 3rd shift; how can I speed up this shift? - Chevelle Tech
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Transmission & Driveline Transmissions and Differentials

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  #1  
Old May 6th, 07, 12:24 AM
Rick Johnson Rick Johnson is offline
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Default 700R4 2nd to 3rd shift; how can I speed up this shift?

Looking for some advanced technical information on 2-3 shift timing:

I data log RPM during my 1/8 mile runs at Irwindale(appro 7.26 ET). I had to slow my car slightly so all shifts now occur in D3. My 1-2 shift is very sharp, but my 2-3 shift is slightly lazy - but does not flair at all. I realize that 1-2 is just a band engagement while 2-3 is a combination of band release and clutch engagement, so maybe I can not have as sharp an RPM drop during the 2-3 shift. I am hoping the trans experts help me out so I can be sure I am doing everything right. I am no threat to the great rebuilders who help with this site, just an enthusiast that rebuilds and tunes engines, trans, diffs, suspension, etc.

My Det (WOT) line pressure in D3 is 225PSI (I just fine tuned this due to a minor flair at 170PSI). My 1-2 band feed orifice is .110 and I have the Corvette servo with the Trans-Go modifications. My feed to D4/D3 which goes through the manual valve, then to the 2-3 shift spool, and then on to the 3rd clutch is .116.

Is this .116 orifice 3rd clutch orifice large enough? Can it be larger?
Could I be loosing flow through or around the white rings on the input shaft?
Is there some other restriction in the path of the 3rd clutch oil, or a restriction to the release circuit of the 2nd servo?
I see posts discussing double feeding the 3rd clutch, but I think they are for another trans?
What changes would best ensure fast oil flow to the 3rd clutch?

Thanks, any ideas would be appreciated!

Last edited by Rick Johnson; May 6th, 07 at 1:13 AM. Reason: clarity improvement
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  #2  
Old May 6th, 07, 2:36 AM
jakeshoe jakeshoe is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

What is the servo travel/band clearance.

No way to dual feed a 700.
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  #3  
Old May 6th, 07, 10:11 AM
SSuper Dave SSuper Dave is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

I don't think you'll ever get a 700 to go 2-3 as hard as it goes 1-2. I've had several that were pretty extensivley beefed and none of them did, and the tranny man at my old dealership said he's never gotten one to do it.
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  #4  
Old May 6th, 07, 10:25 PM
Rick Johnson Rick Johnson is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

Maybe it is shifting well enough. Since it was 'flairing' at 170ish PSI, but completely OK at 225PSI, I am just trying to ensure I have enough clutch life safety margin and understand if there are any basics I do not understand.

[quote=jakeshoe;1337179]What is the servo travel/band clearance.

Unfortunately I do not know the clearance at this point. I also do not know how I establidhed the clearance 5 years ago when I built it.

I remember that the 9 clutch Alto 3rd gear had very little clearance and I remember being shocked that the literature said to allow a very tight number (probably about .015 or less). Unless the clutches really wore out, I doubt the excess shift time fill time is spent at the 3rd clutch. Maybe your question is suggesting the shift time is lengthened by time spent filling the servo chamber as the 2nd band is being retracted. This would make sense to me.

When the valve body was out recently I remember removing the band anchor and noting that the band was very loose, but did not try to put a number on it.

Could excess 2nd servo clearance from a short pin cause this?

How do you set the band clearance without the special tool? How much clearance should there be?

Can I somehow direct a higher volume of oil to the 3rd circuit to compensate for excess clearance, or do I have to reduce clearance?

Thanks for all your help!
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  #5  
Old May 7th, 07, 12:53 AM
jakeshoe jakeshoe is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

The 2nd servo is the 3rd accumulator. Excess clearance of the servo/band, will cause a slower shift. Tighten the clearance.
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  #6  
Old May 7th, 07, 12:14 PM
Rick Johnson Rick Johnson is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

Thanks for the help.
On band adjustments to other transmissions, we are told to tighten a screw to a specific torque and then back of the adjustment a specific number of turns. Since I do not believe this is possible in the 700R4, what range of clearance am I looking for with this band?
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  #7  
Old May 7th, 07, 12:57 PM
jakeshoe jakeshoe is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

.060" servo travel.
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  #8  
Old May 7th, 07, 2:31 PM
Rick Johnson Rick Johnson is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

Thanks, you have been extremely helpfull. I will rest (and sleep) better with this knowledge.
Please answer me one final question. A local rebuilder told me that the 9 disk alto clutch pack I used does not dissipate heat well enough because the metal plates are too thin. Another said they will warp in a performance application and then drag causing more heat. At some point I will rebuild this trans again and want to use the best parts.

What is the best 3rd gear clutch pack arrangement these days and how much clearance should the clutch pack have?
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  #9  
Old May 7th, 07, 2:46 PM
jakeshoe jakeshoe is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

Raybestos Z pack or an 8 count pack using the stock Hi-Energy plates and thick steels.

I like to have about .050".
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  #10  
Old May 7th, 07, 4:56 PM
Rick Johnson Rick Johnson is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

Thanks!!
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  #11  
Old May 7th, 07, 10:12 PM
jay jay is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

Rick, I've used this Sonnax part# 77701-076 to improve the 2-3 shift. It works great. Go on their site and check it out.
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  #12  
Old May 8th, 07, 2:32 AM
Rick Johnson Rick Johnson is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

Quote:
Originally Posted by jay View Post
Rick, I've used this Sonnax part# 77701-076 to improve the 2-3 shift. It works great. Go on their site and check it out.
Jay,
I searched and could not find this number.
What is the basic idea of this kit, maybe I can find it by a description.
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  #13  
Old May 8th, 07, 2:43 AM
jakeshoe jakeshoe is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

It replaces the stock capsuled checkball that feeds and exhausts the servo. You can also block this passage off with a cup plug.
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  #14  
Old May 8th, 07, 10:50 PM
greg5436 greg5436 is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

you can also install the shift technology super servo.easiest thing to try with only removing the servo. greg
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  #15  
Old May 9th, 07, 10:25 PM
jay jay is offline
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Default Re: 700R4 2nd to 3rd shift; how can I speed up this shift?

Rick , sent you an email with info on the Sonnax valve.
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