Full throttle upshift question

B

Blake

Guest
How common is it for SyTy not to have full throttle upshift from 3rd to 4th?

I was digging through the archives and found a post that said our valve bodies were supposed to be able to shift from 3rd to 4th at full throttle.

Sonnax has a special HD throttle valve plunger and sleeve kit that has eliminated the part throttle sleeve orifice allowing a full throttle upshift from 3rd to overdrive. Here's a link:
http://www.powerglide.com/parts/parts/77966-94mk.htm
Do we need it? Sounds like most guys out there are hitting the fuel shutoff in 3rd and not getting top end of 4th.
Blake
 
jwaller

jwaller

Evil Genius/SyTy Guru
your stock trans is supposed to upshift into 4th @ WOT....but when your trans begins to wear out this is usually one of the first signs.....you can swap to the sonnax part and it will probably restore your upshift. but your trans is going to need attention sooner or later...
 
B

Blake

Guest
So is the Sonnax part just a band aid? I'm getting ready to go throught the whole tranny and would hate to get it all back together only to have no 3-4 upshift at wot. Right now, it has over 120K on it and I'm kinda afraid to go wot for fear of breaking something else that otherwise might have lived. In an old thread I found, I did find that SyTys were supposed to have the 3-4 upshift capability but some my have the wrong throttle valve sleeve due to QC problems.
We already found a #4 apply ring in Jesse's Sy during the rebuild. GM had a #7 that was stronger but for some reason didn't put it in Sy #1178. However it DID have the HD rear planetary with the oil slinger on it. Hmmm.
See what I mean? Can I tell by looking at the sleeve on the throttle valve in the valve body?
Blake
 
jwaller

jwaller

Evil Genius/SyTy Guru
yes the WOT sleve will have a 94 stamped in the end of it where it meets the TV arm..and yes this is a band aid but the sonnax is a better part and will be a good buy in the long run....and just for your knoweldge dont but anything directly from them...you can find it for half what they charge...:smile:
 
Tooky

Tooky

Serious about performance
For the record, I have Sy #0044 with 37K miles and the original trans AFAIK, and it always upshifts to 4th (OD) at WOT. Somewhere right around 96 MPH.
 
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