Howdy all

I have an 86 Bronco with a freshly rebuilt 300 inline 6 and a C6 transmission. 3.55 gears and 31" tires.

I replaced the vacuum modulator on the c6 when we rebuilt the motor, and the old one had a lot of transmission fluid in it. I installed the new one, and was disappointed in the shifting - very, very soft. At wide open throttle from 1-2 and 2-3 it shifts at almost exactly 3000 rpm, (which may be normal, I've never been in another rig with this engine/transmission combo) but the shifts are really soft - like if you weren't watching the tach you might be wondering if you shifted at all. I know from reading other posts that the C6 is a soft shifting transmission when stock, so I've purchased a shift kit (and will be doing plenty of research before putting it in - first time doing any of this stuff) and am hoping that will give me a more positive shift.

My worry is that when I removed the line to the vacuum modulator to try to see if I could adjust the shift points up (my hands are too big to get between my headers and the frame with the screwdriver) I had some auto transmission fluid in the line again - enough to make a 50 cent size puddle on the ground. Since the modulator was new less than 500 miles ago, I'm assuming that it wouldn't be that. Does anyone have other ideas as to what would cause fluid accumulation in the line?

Thanks in advance for the help

 

The previous modulator with a leaky diaphragm allowed trans fluid to coat the steel tubing and all rubber vac hose involved all the way up to the intake manifold vac port. Disconnect it all, blow out steel tubing from the engine compartment end, solvent will help clean it out good. Then replace all rubber vac hose involved, as the ATF will affect the rubber over time, and rubber hose isn't worth trying to clean, even if you could.

About C6 modulators, there are different C6 modulators identified by color stripe, but I don't remember the differences anymore between them.

 

Is anyone else astounded by the notion of wanting an automatic transmission that shifts "harder"? Since the dawn of the "automatic" it has been the goal of every manufacturer to make the shift points in an automatic as smooth and unobtrusive as possible. Many an automatic has been redesigned to improve and smooth out shiftpoints over the years. To that end, some manufacturers have even made the jump to "shiftless" automatics which operate on the principle of variable diameter drive pulleys like snowmobiles have had for ages.

I just marvel at the idea that one would hope to make the shifting in an automatic more obvious/obtrusive. Just the thoughts that entered me head upon reading these "concerns". If my automatic shifted that smoothly after however many miles by just replacing the regulator I'd be tickled with it. But maybe my idea of an automatic is disnointed.

 

Thanks Torky, I'll blow those hoses out and see if the fluid comes back. Hopefully I'll also be able to find a screwdriver and an approach angle that will allow me to adjust the shift points on the transmission.

Greystreak, the reason I'm looking at a shift kit is that I have heard/read about the benefits that include reduced slippage, decreased temperatures, increased service life, increased economy, and, this is the one I was looking for, helps remedy early shift points. I'm not looking for a neck snapping shift, but I am hoping that it will give me a little better performance from my transmission by allowing it to rev slightly higher and shift a little quicker. There may be easier/better ways of doing this (without switching to a manual gearbox-I'd love to do it, but it's a bit outside of my budget and abilities at the moment). If there's a better route to my goal, and I'm barking up the wrong tree with the shift kit idea, then please let me know. I'm not afraid to admit I don't know much about transmissions, and I'm happy to learn.

 

Its all good. I'm actually not a fan of slush-boxes in trucks in the first place. (ZF swapped in my own from and E4OD) I was just musing on the prospect of making an automatic do something it was engineered to avoid. You are definitely on the right track if you are looking at improving for towing and power applications. Shift kits can certainly "wake up" an otherwise "slushy" automatic.