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Discussion Starter · #1 ·
Looking for Build tips for my C6 for my 77 F250 4x4 . 460/521 ,,,35 inch tires and 4:10. I'd like to tow no more than 10,000 lb trailer very rarely. 3-4 times a year..
I have the Divorce mount T case.
So far I'm planning on the 5 clutch set up .
I've ordered the CK Performance low drag roller 6 pinion kit . I'll definitely be able to use the lower 1,2 gears
Off road with aired down tires.
Now I've read alot of excellent information here about building a C6 from F Merkel, Greggaust and others.
I'm not always sure if some of the particular info pertains to "Drag Race only , manual VB / Trans break applications "
I happen to have the R Code servo from sonnax and the Superior R Code servo.
I was using the Unmodified Sonnax with an F code and lightest spring in my last C6 build. It shifted WAYYY To hard on the 2-3. Possibly Binding..? Ended up smoking the band , drum and some clutches after only 5000 miles.
Originally there was some type of shift kit in this trans ,and was using the S Servo and A apply In that build. I think the truck came with that in 77.
Shifted Good and lasted from before 94 till 2008 when I lost a pinion bearing and made some metal.
So I'm in the process of Having my C6 gone through and was looking for tips on what clutches, Servo and spring combination to use.
I do have the E apply lever, That I'd like to try with one of the code servos. I do like firm shifts. Not neck snapping though. !! Lol!!
Any help or tips for a performance style 4x4 non drag race Truck build that gets driven pretty hard at times off road would be great !
Thanks in advance!!
Paul
 

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The R servo and E apply should work good for you if you don't go crazy with valve body mods.Extra clutches and #9 roller like in Frank's deal would be nice but I would stick with a more driveable shift kit like Transgo SK6.
 

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Discussion Starter · #3 ·
I appreciate your help. I'll take a look at the Transgo SK6 shift kit.
I do plan on extra clutches. 5 in the drums.
All Roller and using my stock servo Spring as mentioned by Frank.
If my spring turns out to be one of the correct diameter stock springs.
Hopefully get 5 full thickness clutches in my drums.

Any thoughts on using the Sonnax or Superior R code ?
 

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I've used both servo's . Really the Superior I like best . It fits straight in and works .
The Sonnax are nice but every one I have used has needed machining , they're too tight
 

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Discussion Starter · #5 ·
My Sonnax was too tight in the case as well ! Installed it in 2008. And never knew about modifying it.
I just tried the Superior Servo last night. FITS PERFECTLY!!! Right out of the box.
So my question now is , for my type of build,, No Trans brake , and column shift.... Shift kit only truck application..
Should I use the Superior Spring with the Superior Servo... or my Factory Spring.. wich is a Green striped paint ,,, .150/ .149 Diameter spring. With the Superior Servo..
The Factory spring seems like it has a more aggressive rate than the Superior Spring by feel.
I do have the E lever installed.

Thanks again for any help. I really appreciate it.
 

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Good question.. That factory spring will be like 60lbs installed .. The superior spring is 25lbs . Yes I have tested all the different springs in a valve spring tester.
(The Sonnax springs are 20lb & 30LB)

Now I recently did a build , superior servo and factory spring , full roller , 5 clutches in each Transgo 67-2 kit worked good as far as I know I haven't personally driven the car .

I'm currently on a 2nd build using the Broader RMVB and Jay said to use the Superior spring with his valvebody . I can't report back yet as to results but I trust his advice .

For your HP and Torque I'd be looking at the Transgo 67-2 kit or if you want more flexibility to tinker with the shifts , Jay @ Broader does a kit similar but gives about 5 different options for shift firmness . Go with the factory return spring in the servo.

The Sonnax servos are fine once machined
 

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Discussion Starter · #7 ·
I appreciate your advice Greg !
I'll definitely post on how my setup works out .
And will be interested to hear how the 2cnd C6 build you spoke of turns out.
I've done plenty of reading here and there is so much good information from people .
Thanks again!
 

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Discussion Starter · #8 ·
Question, My Sonnax Servo was never modified and I was using it . Along with the Lightest Sonnax Spring... and ,,
with an E lever. ( I verified wich lever I was using,, earlier post I wrote F. )
This build lasted about 6000 miles before completely loosing 2Cnd gear. It wasn't slipping. It just all of a sudden lost 2cnd, and the Temp shot up to 250. IMMEDIATELY.
Didn't break the ears off the band either.
Usuall temp is 150-200
All other gears worked fine.
The temp went back down after ten minutes.
And was able to get home using 1st and 3rd.
So , maybe the sticking servo piston and light springs caused the extreme hard 2-3 shifts ?
And was slowly burning up the band and drum?
Whatever type of shift kit that's in this valve body , since pre 1994 was not changed in the 2008 build.
Any ideas as to why the failure.?
1-2 shifts were good , not tire chirps with 410s and 35 muds.
Paul
 

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I've never had one of those servo's that hasn't needed machining. All have stuck in the case and that's with the factory spring..

That would of been your issue for sure . The hard shift with have actually been a bind on the shift that made it feel hard.

I've never used those light springs with the Sonnax servo . I've recently switched to the Superior servo. used a few now they work nice in the case. Not that machining is a big issue but is a pain to have to rectify a part you pay good $$$ for .

One tip also when testing the piston in the case be sure to use transmission oil . Assembly lube is slippery and they can feel ok . I nearly got caught on one . Was ok with the lube but with type F the piston would stick in.

Most of the different shift kits do similar mods to the same valves . I've usually use Transgo 67-2 if I'm going with a basic kit , then add a couple my own tweaks.
Another tip that might of caused your issue . Need to be sure and measure the manual valve position during assembly. There is a point on the manual valve that on a 3-2 manual downshift can apply both gears at once . That too will smoke the band and high clutch. I can elaborate more if you need ..
 

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Discussion Starter · #11 ·
Very interesting Greg !! That's when I lost 2cnd gear... during a manual 3-2 downshift...
Then full throttle and no more 2cnd gear... that's when the temp shot up to 250... IMMEDIATELY!!

Yes , if you could elaborate more on the measurement concerning the manual valve when assembly I would definitely like to hear !
I will definitely try the Superior with Type F. Not trans goo lube.
I've looked at both the Transgo Sk6 and 67-2. after I determine what was done to this valve body previously,,, pre 1994...
I think the 67-2 might be a good choice for me.

Thanks again for the info!!
Hope this helps others on here as well!!
Paul
 

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The Superior servo's I've used have been good . See what is in your valvebody now and go from there . May already have some kit in it ..

As per pics below. The 1st pic shows how it should be . That port needs to be open in 2nd gear . Usually you will get a measurement of arount 17-17.5mm to face of Valvebody . Or around .750" to the bottom of the chamfer ..

The next pics show a trans with this issue, if you have between 15-16mm in "2" , as per the last pic you can see that port not open enough. That is where the high/reverse clutch needs to exhaust to release 3rd gear

92784
92785
92786
 

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Discussion Starter · #13 · (Edited)
Thank you very much for clarifying!!I will definitely check this measurement out . And will report what I find.
As per the valve body, this must have had something done to it by the previous owner.
When i bought the truck in 94 , with the 2 barrel 400M ... it shifted really good,,. Hard 1-2. And good 2-3. That was With S code servo and A lever.. and Factory Green spring.. .150/.149.
After installing my 1St 460. Rv style cam , CJ iron dual plane..
And using the same exact Converter. ,, it didn't shift as hard as when the 400 did 1-2. But still shifted GOOD. 1-2 And 2-3 I suppose the torque of the 460 changed things up .
Paul V
 

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Hoping for help on c6.

Am cobbling together a shifter for c6. Can anyone tell me degrees of rotation of shift shaft for each shift? Are they all the same? PRND21
THANKS
 
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