My transmission / rear end (C6, 2.75 gears) is shifting ~ 5600 or so.

Is shift RPM adjustable somehow on the tranny? I'd like to go to 5800-5900. I have a full roller setup and Comp double valve springs...factory rods are reconditioned and shot-peened...all fasteners are ARP...so it should be good for that - maybe even 6,000 safely. Thoughts?

Door jamb tag:
Axle: 2 (2.75 rear end gear ratio)
Trans: U (XPL C6 tansmission)

 

I found this thread...DanLee, did adjusting that screw clockwise raise your shift RPM to your satisfaction?

https://www.ford-trucks.com/forums/4...-4000-rpm.html

 

.. First, you have to decide if current shift points are OK for general driving and just hold gears manually for racing (I assume they can be held without being eventually overridden!)... or if want shift points higher in Drive...

.. I had my C6 rebuilt, but never really looked at it closely... always assumed it had a 'passing gear linkage' to carb. linkage that could be adjusted for different shiftpoints/kickdown RPMs like 1950's GM trannies... never occured to me it had a vacuum servo like a GM TH350... usually, the weights/springs in the governor are changed for even further shift point changes... maybe increase fluid line pressure to the clutches for higher powered engines... guess this will be an interesting/educational topic on the C6 as well...

.. A 'Ford guy' rebuilt my C6 and claimed C6 was the strongest tranny made... of course, we also know now the C6 has the most internal drag/friction... eating up like 66 HP at 6,000 RPMs... 34 HP for a C4 or TH350... 44 HP for a TH400...

.. 200-4R tranny in my '86 Monte Carlo LS shifts at only 4000 WOT in auto mode, prolly to help gas mileage... but the LoPo 305" V8 actually pulls to 5,000 or so with good power when held in gears manually... lifters pump up about 5100... the SS version shifts around 5500 in auto, but the SS 305" engine also has a bigger cam/valve springs...

 

.. Shane,

.... You still alive out there?

 

Yes!

I had a new vinyl top put on the LTD, and just put the interior back in. It was musty and nasty due to the roof having leaked under the vinyl soaking the carpet.

Everything is running pretty good...I have two issues I still need to research / resolve...

The most important is I have a bit of pinging at WOT...so obviously I need to back off total timing a bit. My initial timing (dist position) is set at 15 degrees; I'll probably back off to 13 or 14...may need to go as low as 12. That may involve another re-curve to get full advance in by 3500 RPM. I have a sweet MSD #8350 pro billet with vac advance on it, so I can adjust curves / stops / vac advance to get it just right. Once I get it perfect, I'll post up my settings and spring colors.

Issue #2 is the tranny shifts before 5800 / 6000; I want to run the RPM's higher. I'm going to talk to my local tranny shop; they are experts on these and rebuilt it for me a few years back.

 

I'm going to try an ATP FX194 / NAPA 14657 black stripe adjustable A/T vacuum modulator. About $30.

NAPA AUTO PARTS

 

.. Did you also have to repair a rust hole in the metal under the vinyl top?

.. An ounce or two of kerosene per tank of gas will usually cure the pinging if the engine really needs the previous amount of timing for full power. What's your max advance with 15 degrees initial?

.. Please let us know if the adjustable modulator did the trick of raising shift point RPMs.

.. Weather reaching 50's up here now, so hope to start getting some things done on the 351M/400/C6 in '78 F150... SuperCab and 8' bed, too long to fit in our garages... even longer with snowplow on... needs brake line under engine grease replaced (fun) and drip at fuel filler tube/hose/tank sorted out first... maybe a body mount replaced on frame...

 

I did indeed repair a rust hole.

Had a good day today...put all-new cluster bulbs in and repaired my turn signal cam so the lever stays latched...also replaces the flasher, so it now flashes at the correct rate.

My timing was 15 initial and ramped to 33 @3,000...

I have re-timed it to 12 initial, and ramping to 30 by 3,000. I'll report back if that solves the ping issue.

 

.. 12 & 30 may be enough with the Aussie 2 bbl. fast burn heads...

 

Alright, here is the skinny on my timing:

I am running the MSD #8350 Pro Billet distributor right now.

I have it set up as follows: 12 degrees initial
1 heavy silver and 1 light silver spring (two steps quicker than the slowest advance curve - 2 heavy silver (slowest advance) curve is factory). As stated above, that spring combo is giving me 18 degrees additional advance by 3,000 RPM (30 total at 3,000)

I have the blue (factory installed) stop-bushing which is 21 degrees advance limit.

So...with twelve initial, my max mechanical advance at WOT is 12+21 or 33 total. I am still getting some pinging at WOT. So...

I have decided to change the STOP bushing from the blue to the black (18 degree limit). This will limit my total additional centrifugal (mechanical) advance to my baseline +18.

I am planning to leave initial at 12, it should still ramp to 30 by 3,000 with no additional spring change, and 30 should be the total then (12 initial +18 at the stop-limit).

I have the vac advance hooked up for mid-throttle cruise, but at WOT it is my understanding that vac is not a player (I am of course disconnecting / blocking the vac advance during tuning).

I did some additional reading, and learned that quench-style low volume combustion chambers require less timing (they don't tolerate high timing), so my issues are in-line with my build using the Aussie 59CC 2V quench heads.

If I have no ping at 30 total, I may try bumping up initial a degree or two to 13 or 14 again (for a total of 31 or 32 at high RPM WOT - still a degree or two less than where I am now).

I'll report back whether or not the 18 degree stop bushing solves my WOT pinging or not. I am VERY close to a solution, as going from 15 initial to 12 initial with no other changes helped significantly. There is just a hint of pinging, and ONLY at WOT @4000-5000RPM.

Tim Meyer, if you read this post, I would be interested in learning your typical initial timing, ramp-up, and total timing you usually employ in these builds.

I should probably do a dyno pull with a wide-band sniffer to make sure that my A/F ratios are fine at WOT...may have to re-jet if I am lean, as I know that can cause pinging as well.

 

Do you have an EGR? Your problem sounds like a lean mixture at WOT. That could be from no EGR, as well as a fuel problem.

A wide band could help. I use an Innovate LC-1 with an Innovate A/F gauge.

 

Hmmm, I have no EGR. I do indeed own the very same wide-band you have (Innovate LC-1) with a G3 A/F Gauge. Perhaps I should install it and take a reading...but I am feeling lazy, so I might just pay my buddy to throw it on the dyno. He has a $1,000 wideband setup that is amazing.

I do want to get it to pull to 5,800-6,000 first though, so I have to solve my low shift RPM issue before any dyno pulls.

How much (max) timing do you think this build should tolerate with 93 octane?

 

.. Hard to predict what timing you can use with 93 octane without knowing the A/F ratio involved at pinging RPMs range... what color are your sparkplugs burning at in easy driving and at hard driving? Sparkplugs in too high heat range can also cause pinging... the plugs you used back in low compression ratio days may be too hot now...

 

You say that the pinging occcurs at WOT, but is that at low RPM & High Load, or higher RPM?

Pinging at low RPM & High Load indicates too much advance too soon. The cure is to install the EGR, or slow the advance curve. Your total advance may be OK, but it comes in too soon.

 

Down low it is fine; only pinging at high RPM at WOT...~ from 4000 and up.

I put the 18 degree advance stop in today but didn't gave a chance to go flog it. Will do it tomorrow.