servo piston

[gdiwicker]

Hey All,
Is the servo piston in the trans a 'hard part' or can you rebuild it? I need to know how to proceed cause it's causing a hard shift from 1-2nd. I thought it was the servo spring before I pulled it out but the spring was not broken. The piston is STUCK. I tried everything I could think of to get it to budge but nothing happened. Also, if I have to replace it, is it a readily available part or do I need to find a doner from another 700r4?

 

[bezerk]

Re: servo piston

dude. 700r4's in syty's must have a hard 1-2 shift.!!!!

 

[gdiwicker]

Re: servo piston

For sure they do but this shift is really hard! It's really a hopeful mindset of ,"Hey this part being fixed could make this tranny work and feel better."

 

[bezerk]

Re: servo piston

it is discribed as a neck breaking shift, sounds fine to me.

 

[gdiwicker]

Re: servo piston

Also, at what speed is 1st supposed to shift from?

 

[bezerk]

Re: servo piston

depends on how deep your throttle is, i wouldsay around 20mph cruising

 

[gdiwicker]

Re: servo piston

yeah, that's exactly where it shifts at most times.

 

[gdiwicker]

Re: servo piston

OK, problem solved. The servo piston got replaced with another piston. Had to buy an entire gasket set for the project to be done but the materials are under 60 bucks. If your trans shifts real hard from 1-2 but not so much to the others, check out this fix. It's night and day.

 

[midnightbluS10]

Re: servo piston

Which servo did you replace it with? Just a plain jane intermediate servo?

 

[gdiwicker]

Re: servo piston

Stock Servo. I didn't want to throw performance parts on it when I didn't know exactly what was wrong. Diagnose first since everyone was telling me that a hard shift is normal. Well, I went for it bc the trans was throwing me forward 1-2 but not the other gears. I just couldn't believe that GMC would make a truck that sucks to drive under normal conditions. I can probably get you the part number later tonight.

 

[Foot Performance]

Re: servo piston

Stock Servo. I didn't want to throw performance parts on it when I didn't know exactly what was wrong. Diagnose first since everyone was telling me that a hard shift is normal. Well, I went for it bc the trans was throwing me forward 1-2 but not the other gears. I just couldn't believe that GMC would make a truck that sucks to drive under normal conditions. I can probably get you the part number later tonight.

If you put a "stock" 700r4 servo in. It is wrong our trucks use the corvette servo and mine shift hard but you will know in a couple hundred miles if you fixed it. if you loose 2&4 you will know you didnt :tup:

 

[dgoodhue]

Re: servo piston

If you put a "stock" 700r4 servo in. It is wrong our trucks use the corvette servo and mine shift hard but you will know in a couple hundred miles if you fixed it. if you loose 2&4 you will know you didnt :tup:

Yes our stock 1-2 shift should feel like a shift kit (shift kit is actually usually slightly softer) 2-3 and 3-4 should be firm but not as nearly as firm as the 1-2.

The parts catalog should call for a Corvette Servo in our transmission. If the dealer or trans shop was lazy and didn't look it up and just threw in another servo then you really need to put back in the stock/corvette servo. Do not go WOT if you don't have the correct servo!

 

[turbodig]

Re: servo piston

What they said - 'vette servo was stock in our trucks. If they didn't put that in, you'll eat up a band in a hurry.

If you had the Superior/Fairbanks super-hold 1-2 in there, a *really* hard shift would be "normal".

 

[bezerk]

Re: servo piston

thanks for listning and good luck with your rebuild

 

[Quickstop [UK]]

Re: servo piston

thanks for listning and good luck with your rebuild

:rotf: