FGS vs SGS valve body - manual/literature/PDF?

[Duh_Vinci]

Cheers all!

When I rebuilt my 722.3, I found ATSG manual to be very useful, however, it does not seem to show any differences between FGS vs SGS related to the valves and plungers etc.

Is there any documentation to what are those differences by chance? Any leads to this information/documentation would be greatly appreciated. Secretly, not knowing the specific difference bothered my since the Dec of 2018...

Regards,
D

 

[gsxr]

Valve & spring #44 are different between FGS and SGS. Although the photo below implies that you can just put the spring on the other side of the valve and magically obtain FGS, this is not the case. The valve (plunger) is not the same.

 

[Duh_Vinci]

Valve & spring #44 are different between FGS and SGS. Although the photo below implies that you can just put the spring on the other side of the valve and magically obtain FGS, this is not the case. The valve (plunger) is not the same.

View attachment 140914
View attachment 140915

Thanks Dave!

I've seen that first "colorful" picture while back, maybe on pelican, while searching for the answers, and as you stated, the consensus were that it is not as simple as just removing or moving the spring...

I've also saved this page/illustration from ATSG which shows NO spring in that booster valve assembly (assuming this is FGS VB illustration?)



I was hoping to find side by side illustration/comparison of the sections of difference... Someone had to crack those plunger sections opened and looked at them side by side, but no photos anywhere, and possibly successfully modify SGS into FGS? I mean these 722.3s been out for years and years... And couldn't help but wonder is there anything else involved in modification of one (other than the booster valve assembly)?

I now have a spare FGS and SGS bodies at home, I may just have to open those up and see the difference "in person"

As a side note, as I was looking through the ATSG manual, found this piece of information for "fine tuning the shift timing" that never noticed before:



Regards,
D

 

[gsxr]

Nobody has posted photos of them side by side, that I'm aware of. It's on my to-do list. I think I have a loose FGS valve but I need to extract the same SGS and put them next to each other. Even if the FGS valve will fit into an SGS VB, you still need a complete FGS VB to get the valve & spring.

The shift adjustment thing generally is never messed with, unless you are having WOT upshift problems. If set too high, the engine computer will hit the rev limiter before the transmission completes the upshift, which isn't fun. And if set too low, you are missing out on some acceleration & power.

 

[Duh_Vinci]

Nobody has posted photos of them side by side, that I'm aware of. It's on my to-do list. I think I have a loose FGS valve but I need to extract the same SGS and put them next to each other. Even if the FGS valve will fit into an SGS VB, you still need a complete FGS VB to get the valve & spring.

The shift adjustment thing generally is never messed with, unless you are having WOT upshift problems. If set too high, the engine computer will hit the rev limiter before the transmission completes the upshift, which isn't fun. And if set too low, you are missing out on some acceleration & power.

That's good to know, great info! "Don't touch that button"

I have a spare FSG soaking right now, about to do the same to the spare SGS valve body, may have these valves out this eve for comparison... I could have sworn that Jono said in some thread here, that they modify valve bodies for their customers...

Regards,
D

EDIT: of course, these valves are secured by the "cotter pin" and requires to actually crack the valve body opened by separating top and bottom (couldn't be the one behind the metal plate with 2 screws that one does not have to do the extra work)

 

[gsxr]

EDIT: of course, these valves are secured by the "cotter pin" and requires to actually crack the valve body opened by separating top and bottom (couldn't be the one behind the metal plate with 2 screws that one does not have to do the extra work)

... and that is why I haven't done it yet. PITA to access! Don't drop the ball(s).

 

[Duh_Vinci]

... and that is why I haven't done it yet. PITA to access! Don't drop the ball(s).

Ohh, but I have the extra set

So, I've cracked both open, definitely not the same Governor pressure Boost valve (but also difference in Governor pressure Shift valve)...

Boost Valves side by side



Close up



Here are some differences in the Governor Pressure Shift valve:





and the top view of the same





FGS has 17 balls, SGS has 18 balls (at least in my samples) if it makes a difference...

So I would definitely question anyone who says simply remove or move the spring forward to convert SGS to FGS

Regards,
D

 

[gsxr]

Great work, D!

Can you tell if the FGS valve will fit in the SGS VB and move normally?

Removing the spring from a SGS VB does indeed provide FGS, but has a nasty side effect of skipping 2nd gear unless you manually shift every time. I would never, ever recommend that downgrade.

 

[Duh_Vinci]

Dave, physically, that boost valve does fit, and depth of the housing orifice is the same. Openings/slots at the top bottom portion of the valve body also appear to be the same size and placement. My guess would be is how the fluid flows as this valve moves, in steps, allowing it to NOT bypass the 2nd gear via these areas:



I almost think a good machine shop would be able to make this valve to specs at a more than reasonable cost and quickly (we used lathe very often in middle school in mid 80's for "home economics" I guess that's what it's called...) to make similar tooling and tools. The question would be the strength of the spring from SGS, is it appears to be a bit heftier than FGS.