Differences between Superior and Sonnax R servos

My current c-6 has one of Franks Trans brake valve bodies .It has been a great performer .I just haven't been happy with my 1-2 shift .I have been using a cut down sonnax for several years .It was cut I believe .014 on the big end o ring groove it goes in the case and works fine I believe part of my problem is the end that goes into the cover it is tight .I measured the piston and bore and come up with .001 clearance .This is just a caliper measurement no inside mics or anything special just my caliper .On the Superior servo it is much different the small end (goes in the cover)has .004-.005 clearance And uses a different style o ring .It has a slant cut o ring like a napier second ring for an engine .It goes in the cover easily unlike the sonnax which is tight .The stem on the superior doesn't have those o rings like the sonnax and I measured the big ends on both servos and come up with .002 clearance piston to bore both servos went in my case easily and moved what appeared to be the same .Superior sends a spring with their servo it is shorter than my original ford spring probably 3/8" that is the only thing I am skeptical about .The way I see it though Superior made this servo so they must know something .Superior is the old Fairbanks company some literature says superior some Fairbanks .I also went with a summit brand deep transmission pan .It is aluminum and lo and behold made in America! Everything about it is good quality .Probably in a couple weeks I will find somewhere to test my transmission and will report back my findings .Doug

Good post Doug. I have in the last few C6 I've done switched over to the Superior servo's . They fit nice and no machining required . Those seals on the shafts I don't believe are required . Based on Franks recommendation some years ago I was removing them.

I got both servo's here I must do some comparisons . I have a Sonnax I've had a while for a mates build I have to machine

I normally cut them around the .006-.007" deeper in the groove . Then check it returns ok using the light Sonnax spring. Be sure when trying fit in the case though to use trans oil for lube and not assembly lube . I found the assy lube is slippery and gives a false feel.

As for the springs , I'd say with Frank's valvebody stick to the heavier factory spring as he specifies .
The first Superior servo I used was with a Transgo -2 kit and I used the factory spring .
I've built 2 now using the Broader RMVB complete and Jay said to use the superior supplied spring with his valvebody
That Superior spring only specs out at 25lb installed height .

One thing I did find and wondered about the O'rings on the Superior servo , the green coating does come off while testing. Leaves a normal look black O'ring. No idea what that green coating is .

I think we have covered all the spring pressures a while ago? If not I have specs on all the different Sonnax and factory ones

As it stands I'll likely stay with the superior from now on. The Sonnax is nicely finished and I used many of them but for same $$$ basically why should I need to machine the Sonnax to make it work?

Gregaust wrote:

As it stands I'll likely stay with the superior from now on. The Sonnax is nicely finished and I used many of them but for same $$$ basically why should I need to machine the Sonnax to make it work?

And isn't it sad that a respected company keeps manufacturing them when it is well known they are wrong?

It's like TCI continuing to sell those junk C6 trans brakes.

Norm I called Sonnax once about their servo they just come across as indifferent and arrogant .They did send me a seal kit free of charge .Sadly not all back yard builders have a lathe and really you shouldn't need one .Doug

Exactly right . I believe I remember seeing Frank mentioned he contacted them also .

I object to spending a few 100 bucks on their parts and then spending time making them actually work. I always wonder how many guys don't know and get plagued with issues .
Exactly right on the TCI stuff . I've now had to repair 4 TCI C6's that guys have imported here that just were not right. Internally they kind of had an idea of what they're doing but poorly finished .
Like one when i tore down had .010" endfloat . But to achieve that they had stacked x2  .016" pump gaskets .
Another was missing return springs in the reverse clutch
Another I helped a guy did not shift from day one . Ended up he fitted a complete new valvebody

As I mentioned though , always be careful to check those Sonnax servos with trans oil. I tried one a while ago with blue assy goo and it felt good . Tried with oil and it just stayed right in there.

I'm on my 3rd superior now and happy as

Just need to get my parts supplier here onto them now so can get a better deal

I hear the same stories about TCI I was at summit one day and a young guy was going to purchase a complete tci transmission .I talked him out of it When I was a young guy I would find a core and take it or my vehicle to a good transmission shop and let them do the job .When I started doing my own I would go to that same shop for advise Sonnax should know by now their servo isn't exactly right and I believe they sell lots of them.They just don't care about us c-6 owners .Probably when they quit selling they will finally do something .I did the c-6 in my 73 f250 I used the stock servo and it shifts fine on the 1-2 .I have another car with the stock servo it shifts great too .I got my transmission installed yesterday it will take me a couple of days to get it going and find somewhere to test it .You know Greg keep fixing those fellows transmissions the word will get around and you will have more business .And remember if you need some c-6 parts I have a few .Doug

Thanks Doug. I've had plenty on this year and still more coming into next year

Shame on the Sonnax servo I'll only use them now as a last resort, at least their wide band is good

I wonder though how many guys get caught with sticky servo issues and try to have to sort them out

Some of the Factory servo's depending on what vehicle can work well . I usually stick to the P or L or a D if one comes up.

Yes I have been lazy to post a response .But most will already know I am happier with the results from my superior servo .Not that the sonnax didnt shift good the superior shifted great out of the box and it is crisper on the 1-2 in the pits .And for the life of me I cant tell any difference between either R servo and what ever came original in a c-6 .I wouldnt build a c-6 for a customer and install a sonnax servo though cut down or not .Good luck to you all .You know I built myself a 502 for my drag car and she ran a 6.62 at 3430 .Couldnt get traction changed gears to a 3.70 from 4.10s ran 6.68 and hooking ! Doug

I use the Superior servo in my 57 Ford. I never had to do any machining whatsoever, just dropped it in and ran it. It's an earlier c-6, 1969-70? The only thing I did was replace the F apply lever with a E lever. It really did firm up the 2-3 shift on my trans. Im very happy with it.

I've used quite a few Superior servos now . Work perfect straight up .  It's likely all I'll use in the future also . My parts guy keeps them in stock also is handy

Funny thing is they measure 3.241" on the large land. Perfect size  

Which is exactly where I usually machine the Sonnax to work successfully,  .014" less than the Sonnax that is 3.255" out of the box.

The .014" less on the diameter is the .007" deeper groove specs that Frank was kind enough to share with us many years ago.

On most all stock or a mild build the std. servo that comes with whatever trans. is what I use .Some of my older c-6s cant use an R servo .I fought one of those Sonnax for three months to get a good shift in my drag car .I had it machined and all was good .I dont build transmissons for others just myself .I had rather weld for people it is easier for me .That is how I keep up with everything ! Good to hear from everybody at least we have some new posts .I havent heard from my buddy with the chattering c-6 no news is good news . Doug