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Discussion Starter · #1 ·
There is a valve change so that it will shift into 4th at wot. I have heard that the clutches are small on OD in the 700R4 and if you put the valve in . These small clutches may be a problem. I get the impression that is the reason they designed it not to go into 4th at wot in the first place.
I would like to know what the results of people putting in this valve to go into OD at wot. Any experience with this out there.
 

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Over drive in the 700r4 trans is the band. Same band that is used for 2nd gear. I suggest a Sonnax brand 4th gear servo. It increases holding power.

I am not sure why GM designed the trans for no OD at WOT.
 

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Discussion Starter · #4 ·
You need this Sonnex shift sleeve.


Except for the true Corvette version the 700R4 is inhibited from 4th at WOT, lots of fakes out there. The loads in overdrive on the 2/4 band and 3/4 clutch are very high. Tranny life gets pretty short running 4th at WOT as a regular thing.

Bogie
Thanks for the response- Do you know if it is mostly or just the shifting or is it running in 4th at wot and is there something in the corvette 700r4 to keep it from wearing out.
 

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The actual Corvette 700R4 uses a lot of different components from the regular production versions. There also changes by year, some of them substantial, so knowing what you have is important information.

There is a serial number stamped on at the rear of the right side (as your seated in vehicle facing the steering wheel) of the main case just above the pan rail. This will lead to its date of manufacture and what version 700R4 you have. We can start there, as to what’s in it after being rebuilt if it was no way to know unless you have a build receipt or a person that knows what to look for opens it up.

I run a modified 700R4 in my S15, nothing the factory used but the cases and basic valve body casting are in it. It does hold 4th at WOT but how it treats that can be different. If I launch using WOT in drive 4th it shifts on a WOT schedule which is much later in the RPM band than just cruising around on part throttle. If I’m just cruising along in Dive 4th and mash the pedal to the floor it downshifts to 3rd, allows th engine to rev to the WOT shift point then upshifts back to 4th. Here I do some tricks as it is set up to run converter lock up only in 4th on a pressure switch. This is if it shifts to 4th it also gets converter lock. The exception to this is a latching switch on the shift handle that is pressed to OFF which electrically inhibits converter lock. The reason for this is the converter lockup clutch is nowhere strong enough to carry full engine power. So unless your into replacing converters you do not want this thing functional at full power. The factory system is different as converter lock up is allowed in second and third gears as well as 4th and is inhibited with a manifold vacuum switch such that as the throttle is opened to about 3/4 toward full open the manifold vacuum being used to engage a switch allows a spring loaded contact to open and terminate the circuit. There’s also a brake switch that opens the circuit when brakes are applied. My set up doesn’t use any of that, I depend on a pressure switch at the external end of the 4th apply servo. If the tranny is not in 4th it also is not permitted converter lock up. This assumes that under the minimum 4th apply speed that pressure in this circuit is not present. The shift handle switch also covers any possible bad assumptions in how the 4th apply might have a sneak or failed circuit.

Bogie
 

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Discussion Starter · #6 ·
The actual Corvette 700R4 uses a lot of different components from the regular production versions. There also changes by year, some of them substantial, so knowing what you have is important information.

There is a serial number stamped on at the rear of the right side (as your seated in vehicle facing the steering wheel) of the main case just above the pan rail. This will lead to its date of manufacture and what version 700R4 you have. We can start there, as to what’s in it after being rebuilt if it was no way to know unless you have a build receipt or a person that knows what to look for opens it up.

I run a modified 700R4 in my S15, nothing the factory used but the cases and basic valve body casting are in it. It does hold 4th at WOT but how it treats that can be different. If I launch using WOT in drive 4th it shifts on a WOT schedule which is much later in the RPM band than just cruising around on part throttle. If I’m just cruising along in Dive 4th and mash the pedal to the floor it downshifts to 3rd, allows th engine to rev to the WOT shift point then upshifts back to 4th. Here I do some tricks as it is set up to run converter lock up only in 4th on a pressure switch. This is if it shifts to 4th it also gets converter lock. The exception to this is a latching switch on the shift handle that is pressed to OFF which electrically inhibits converter lock. The reason for this is the converter lockup clutch is nowhere strong enough to carry full engine power. So unless your into replacing converters you do not want this thing functional at full power. The factory system is different as converter lock up is allowed in second and third gears as well as 4th and is inhibited with a manifold vacuum switch such that as the throttle is opened to about 3/4 toward full open the manifold vacuum being used to engage a switch allows a spring loaded contact to open and terminate the circuit. There’s also a brake switch that opens the circuit when brakes are applied. My set up doesn’t use any of that, I depend on a pressure switch at the external end of the 4th apply servo. If the tranny is not in 4th it also is not permitted converter lock up. This assumes that under the minimum 4th apply speed that pressure in this circuit is not present. The shift handle switch also covers any possible bad assumptions in how the 4th apply might have a sneak or failed circuit.

Bogie
Thanks Bogie I will start by checking the serial number and I will get back to you. If that's OK
 

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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I don't have the WOT in 4th gear. It was never anything I was going to need. I can't comment on that.

I do have the 4th gear servo Crosley mentioned. That upgrade is a no brainer for the cost.

My converter lock up is exactly the way Bogie describes. S10 700r4. I can say I'm pleased with how the switch on the shifter does the job and the ease of use.

You have some great resources on this forum. I'm along for the ride and expect to learn quite a bit.
 
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