700R4 Intermediate and OD Servos - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-27-2005, 11:05 AM
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700R4 Intermediate and OD Servos

Looking at an exploded view of the 2-4 servo passages, I can clearly see the two servos (pistons and housings) and I count 5 o-ring seals total.

B&M's "vette servo" type kit seems to show 5 o-rings.

This is an old 700R4 going behind a real low HP motor. But it's in a truck, not really towing anything. Though the last car I towed my Dad fried the current 700 by riding the brakes in the tow car.

I just wanted to update the servo/servos to get a little more apply pressure on the old clutches. Correct me if I'm wrong, but I felt since these use the pressure already existing in the tranny, it's not like I'm boosting it with a Transgo Kit or a boost valve and risk internal leaks of the old seals.

I see vette kits all over the net for as little as $9.84 "complete with o-rings & seals". Am I to assume that means the 4th apply piston and housing o-rings that obviously have to come out first?? I can't seem to "buy" these seals online as an insurance policy. Pretty sure the old 4th apply servo seals, if missing from a "vette" kit, would not re-use right?

My 2nd question was that the 4th gear servo kits are like $80-90. Though I did see a Sonax "piston" for $57. What good is the piston without it's housing? Are these priced high because it's what the market will bear? I guess many like to "tow" in overdrive?

I'm about to re-install this old 700R4 (changing front/rear seals of course) and felt maybe now might be the time to update something (besides a full rebuild, beyond my scope likely). I'd just like to get a little more time before this tranny "bites" me. The servos seemed like a good idea. The cheap vette one anyway (seems to put more force on the clutches other than OD, or at least shift faster for lower temps). But I'd like 4th to last too this time (better apply pressure would be nice). I don't drive it hard at all. Don't want tire chirps on this, but I feel the tranny is too old for a shift improver or even a fluid change possibly. But it does still work. Will be using a good cooler too as always.

EDIT: This is a perfectly functional 700R4 in every way with good red fluid. No signs of failure except the odometer from the donor car that it came from. I realize there is no quick/cheap fix for bad units.

Thanks

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Old 06-28-2005, 01:07 PM
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usually the vette servo kits have the 2 O-rings and the 2 sealing rings.

Reuse the sealing ring on the OD piston , it will be fine


the larger OD servos are billet units , not a cast piece like the vette servo. More money for the billet piece

These servos do nothing to the clutches , it works on the band only
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Old 06-28-2005, 04:42 PM
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Quote:
Originally Posted by Crosley
usually the vette servo kits have the 2 O-rings and the 2 sealing rings.

Reuse the sealing ring on the OD piston , it will be fine

the larger OD servos are billet units , not a cast piece like the vette servo. More money for the billet piece

These servos do nothing to the clutches , it works on the band only
Okay thank you for the info!

I'll re-use the OD servo ring if I don't spring for a billet OD kit. Billet vs cast hadn't occurred to me for pricing...

Okay so these 2-4 apply servos just actuate the band quicker for a faster shift, therefore less clutch slip during the shift, and a tad lower let's say city driving fluid temps right?

So the info around the 'net about 300lbs more apply force in 2nd gear seems incorrect then...

Would you still recommend a cheapo vette cast kit for an old 700R4 while she's out waiting to be installed? It's hot down here and I'd like to do what I can for longevity (quicker shifts I suppose).

Thanks again!
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Old 06-28-2005, 06:12 PM
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300 lbs of additional holding power for the vette servo? I don't know about that.

The vette servo has more surface area to produce more holding force on the band.

You will see/feel a firmer 1-2 shift and the 2-3 shift will quicken up a tad also
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