C6 transmission

[b1isbored]

I just put another c6 transmission in my 1985 Ford Bronco, it worked for a week or two, but today i took it on a little bit of a longer ride, and kicked in my 4 barrel carburetor, ever since that i can shift it down into reverse, and itll chunk into it, but wont back up when i give it gas. Also when i put it into drive it wont go from 1st to second, but i can move the shifter down to second and its fine. what happened and how do i fix this?

 

[Krafty]

did you crush your stater pump when you put the TC in the transmission? and hows your trans fluid level?

 

[b1isbored]

No, I actually had to replace the pump cause i crushed it the first time... it works good til it gets hot, maybe the wrong transmission fluid?? Mercon V is what i put in it.

 

[Seabronc]

No, I actually had to replace the pump cause i crushed it the first time... it works good til it gets hot, maybe the wrong transmission fluid?? Mercon V is what i put in it.

Check the shifter link adjustment where the linkage connects to the transmission. The adjuster nut may not have been tightened enough and allowed the adjustment to slip. I believe that any Mercon is satisfactory, I don't have a bottle to look at, but it should say if it is approved for use in the older transmissions.

>-

 

[b1isbored]

that would keep it from shifting from first to second in drive though? not doubting you, just trying to learn stuff lol

 

[Rons beast]

For what it's worth, MerconV is NOT recommended for your truck. An 88 should have Dextron III, or Mercon.

I don't know if this would cause your problem, but thought you could use the info.

Good Luck

 

[miesk5]

yo,

LATE, HARSH, OR NO SHIFT

Turn kickdown rod adjusting ***** out 1/8th" inch

Check vacuum at modulator

Pull the vacuum line off the mod. If fluid comes out of the vacuum line your modulator is not good.

Cl vac line to modulator

Shift Linkage pics; and 351W with factory Holley by Yardape; and 750 carb by gatorbronco

Source: by J&SBroncolvrs, Yardape, & gatorbronco at Ford Bronco Zone Forums http://broncozone.com/topic/16734-c6-kickdown-rod-linkage/

Vacuum Modulator; "...The vacuum modulator is a vital component of an automatic transmission. It tells the transmission what kind of load is being put on it allowing the transmission to react with the proper line pressures and shift points. Over time, modulators can develop leaks, get ruptured diaphragms, get bent, etc. Not only can this cause annoying drivability issues, it can lead to premature transmission failure..."

Source: by TCI Automotive

Shift Linkage Adjustment Points in 82-86

by Chilton

 

[b1isbored]

ok well fluid did come out of the modulator valve when i took the line off, so im gonna buy a new one friday possibly... would the modulator valve be the cause of that?

 

[miesk5]

yo b1isbored,

yes!

Some fluid may come out when you remove the vac. modulator, but not much. If a a lot comes out, then the tranny was overfilled.

Be ready to top fluid off.

it is VERY IMPORTANT to verify amount of vacuum at the modulator with a gauge. Automatic transmissions typically need a minimum of 12 in. Hg. at idle. Throttle position increases should produce a quick decrease in the vacuum reading at the modulator. Not enough vacuum will cause late, harsh shifts. Slow response to throttle position changes due to a kinked or plugged line will not property boost line pressure and will BURN UP YOUR TRANSMISSION

by TCI

Also check for Vacuum leaks in HVAC sytem (to some doors), at PVC, etc. see my Post about locations to check @ http://broncozone.com/topic/22770-low-idle/

 

[Seabronc]

Also watch out that you don't loose the small removable pin in the end of the modulator, you need it for the new one. You will need to know the color band on the side of the modulator when you go to get a new one.

>-

 

[b1isbored]

thanks for the help!! will let you know tomorrow if it works.

 

[b1isbored]

okay well, i put my new modulator valve in today, same color band as the other one and everything, but same old story.. i get in it fire it up, put it in reverse and it works perfect, go down the road a mile or two and it goes through all the gears... but after it runs for a little bit reverse wont work and neither will third. i put it in reverse though and it kicks back like itll go, but then i hit the gas and it goes no where... so its not the modulator valve, i havent adjusted the kickdown cable yet though..

 

[miesk5]

yo,

Shucks!

check for Vacuum leaks;

any vac leak symptoms such as

Surging,

Rough idle,

rich fuel condition w/spark plug fouling,

Detonation

loss of power and/or fuel economy

Vacuum Leak Test; On an idling engine check for vacuum leaks using a mechanic's stethoscope with the probe removed, or a ~3' garden hose section. On COLD ENGINE only, use propane torch w/rubber hose attached, UNLIT or spray carb cleaner, when it gets to the the leak the RPMs will rise

 

[b1isbored]

yo,

Shucks!

check for Vacuum leaks;

any vac leak symptoms such as

Surging,

Rough idle,

rich fuel condition w/spark plug fouling,

Detonation

loss of power and/or fuel economy

Vacuum Leak Test; On an idling engine check for vacuum leaks using a mechanic's stethoscope with the probe removed, or a ~3' garden hose section. On COLD ENGINE only, use propane torch w/rubber hose attached, UNLIT or spray carb cleaner, when it gets to the the leak the RPMs will rise

is there anyway it could be my thermostat letting my engine and transmission get too hot? ill look for vacuum leaks today and tell you what i find..

 

[Seabronc]

is there anyway it could be my thermostat letting my engine and transmission get too hot? ill look for vacuum leaks today and tell you what i find..

What does the temperature gauge say? Do you have a heat shield between the exhaust and the transmission? a missing heat shield off the CAT? Do you have a trany cooler? What is the outside temperature?

>-

 

[b1isbored]

What does the temperature gauge say? Do you have a heat shield between the exhaust and the transmission? a missing heat shield off the CAT? Do you have a trany cooler? What is the outside temperature?

>-

Well the temperature gauge says normal.. I dont have a heat shield between my exhaust/headers and transmission though.. I do have a transmission cooler..

 

[miesk5]

yo,

check tranny cooler front for dirt; wash off w/dish soap and water; try not to bend fins.

How did the vacuum leak check go?

The vacuum gauge should show around 18-22 in-Hg @ idle & maintain a steady needle

Suggest buying a vac gauge, best low cost test and MPG helper you can spend $ on;

pic; "...a vacuum gauge mounted in or On the dash . I use it to also help determine the load my engine is under while driving, and to estimate fuel economy..."

Source: by William T at http://www.fordf150.net/images/mytruck/vacgauge.jpg