Cascade Crew

IROCDave · Posted: Thu Feb 18, 2010 7:14 pm Post subject: 700R4 question

Which 700R4 transmissions will shift into overdrive at full throttle? I have heard that only the corvette and 5.7 litre F-bodies will shift into OD at WFO. I know for a fact that a bone stock 87 IROC with a 5.7 will go into OD, and that it will do 160ish MPH.
I also know for a fact that my 87 5.0 litre would not shift into OD at WOT. Top speed was in the 130's, but full throttle dropped the tranny into drive.

I bought a used 1992 700R4 and had it rebuilt, the shop said that they could not make it stay in OD at full throttle. I have wondered about this for years, what is different in the 700R4's by specific model that would allow top speed runs in OD? And why cant a lesser 700R4 be upgraded to allow this?

chevymad · Posted: Thu Feb 18, 2010 7:27 pm Post subject:

It can be upgraded, very simply actually. It's just a different TV piston. There's a groove cut in the outside of the piston that dumps the hydraulic pressure when the throttle is past a certain point. Thus preventing OD. Installing a vette tv valve allow full throttle OD. However, this can also prevent downshifting after a certain mph. My tranny likes to stay in OD instead of dropping into passing gear because of this. At some point I'm going to pull the vette tv valve out and replace it with the stocker again. Would much rather have it shift to passing gear then do 160.

Twilightoptics · Posted: Thu Feb 18, 2010 7:46 pm Post subject:

When my '85 was rebuilt, the shop made it so It would stay in OD.

They didn't charge me for a TV cable though, and I recall verifying adjustment shortly after and it was the old dirty one.

IROCDave · Posted: Thu Feb 18, 2010 7:48 pm Post subject:

I dont plan to run my car at those pseeds again unless it is at SIR. But, it would be nice to know that if needed the transmission would shift properly into OD at full throttle. My moms old car did not shift into OD early under full throttle nor did several stock 80's corvettes I have driven. I think there may be more to it than just a grove in the TV piston.

I had a transgo shift kit and corvette servo / TV valve installed in my 87 5.0 IROC when it was basicaly stock, it still didnt shift into OD at full throttle.

Twilightoptics · Posted: Thu Feb 18, 2010 7:54 pm Post subject:

Like Brandon said it's something internal.

From what I understand, no 700 will shift WOT OD from the factory. 3/4 throttle, yes.

chevymad · Posted: Thu Feb 18, 2010 8:07 pm Post subject:

Well, i'm using probuilts version of the transgo kit, and the vette tv valve in an 88 700r4 from tony's gta.. and it definatly stays in OD at full throttle now. You can see the difference in the 2 tv valves when you have them out. At like 60% throttle that groove comes uncovered and dumps the pressure.

Here's the tv valve kit.

http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=2&Product_Code=S74741NCK&Category_Code=4L60-700R4vbkits&Product_Count=4

Pic of the different valve and sleeves. You can see how the different lands on the piston line up differently with the sleeve.. and the grooves on the sleeve line up differently with the orifices in the valve body.

http://www.proshifttransmissionparts.com/images/778_VETT3.gif

I had some more info about how it really all works, but it appears that both sites were on webhosts that are no longer.

IROCDave · Posted: Thu Feb 18, 2010 8:19 pm Post subject:

IROCDave · Posted: Thu Feb 18, 2010 8:22 pm Post subject:

Twilightoptics · Posted: Thu Feb 18, 2010 8:22 pm Post subject:

Maybe I read wrong. You're talking about shifting into OD early? That's a gov issue.

The issues I've had, seen, read is that when you're in 3rd WOT.... it wont shift into OD unless you release to 3/4.

The vettes may be different then as Brandon's saying the Valve is different for them to allow it... Which makes sense. The Vette is God.

chevymad · Posted: Thu Feb 18, 2010 8:29 pm Post subject:

Certain performance models, police cars, and corvettes are the only ones that I know of that had the wot valve stock. But it's been the most common rebuild or shift kit mod for years and years. Is it possible the cars you rode in had a shift kit in them? or trans work done? Or were they a special model?

If you're really really interested I'd send Dana at Probuilt transmissions a note asking about it. He posts on several automotive websites including tgo.

chevymad · Posted: Thu Feb 18, 2010 8:32 pm Post subject:

Here's Dana's own site.

http://www.700r4l60e.com/

IROCDave · Posted: Fri Feb 19, 2010 9:39 pm Post subject:

Seems like the water is muddy. Hopefully this clears it up.

Most most 700R4's will not shift into OD under full throttle. But some did from the factory. They also shifted correctly under less than WOT. The vehicles I have driven that have shifted well in each gear and into OD at WOT have been a 87 5.7 litre and TPI Corvettes.

When I had the transmission built for my car the shop said that they didnt know how to make it upshift into OD at FT.

GM didnt make a specific transmission to allow this. I am wondering what upgrades it takes to allow this without any driveability problems?

chevymad · Posted: Fri Feb 19, 2010 10:28 pm Post subject:

Well the 88 5.7l gta trans didnt have the wot shift.

redlava · Posted: Sat Feb 20, 2010 10:12 am Post subject:

I am gonna have to agree with brandon and paul here. The cars were not designed to go into OD at WOT, this caused a lot of extra stress on the trans. That is why they didn't do that from the factory. The cars you were riding in must have been modified.