Hello,

Been reading lots of good posts and appreciate all the expertise out there. My first post, so forgive the ignorance!

I have 5 Ford trucks now 69, 83,84,84, and 85. Currently working on an 84 F-250, 351W, auto C6 tranny. This one was going to the junkyard for $50 so I HAD to save her! She was high centered in an off-road adventure and appeared to have a fried tranny.

Reverse worked- some slip to O.K., but MAJOR slipping in all forward gears. Fluid was low and dark like old motor oil, but didn't smell burnt.

Brought her home today and cleaned all the mud out. Engine runs pretty smooth I power washed all the mud out. The entire engine compartment and underside were LOADED!

I added tranny fluid to spec, no improvement. Remove vaccuum line from modulator... slight clunk into drive ( beats reving like crazy!) and major improvement, but nowhere near normal.

BTW: no tranny fluid in vaccuum line to modulator.

SO, my question is .... what are my odds and what next?

My thought is to drain the tranny fluid, look for metal shavings. New filter, gasket and fluid. Put in a magnet and maybe a drain kit ( If I think it can be saved!) Test the vaccuum, then replace the modulator if needed.

Sound resonable? Or are these sympthoms of a fried tranny?

Thanks, in advance, for your posts!

 

The only sureway to find out is to drop the pan, and if you have lots of metal shaving, clogging the filter (could be mud in there... in which case its a gonner anyway) take one of the trannies out of the donor yard an not worry about rebuilding it, its cheaper if you got the labor an the trans)

 

Thanks locknkey for the response...

UPDATE - I dropped the pan. 1 piece of metal about the size of a seasame seed in the pan and a dozen smaller shavings in the filter. The filter was not plugged. Replaced filter, gasket and new tranny fluid. No change. Pulled the vac off the modular. I don't have a vac tester or way to measure, but there seemed to be good vaccuum. Reverse works with vac on or off modulator. Forward gears work better with vaccuum off the modular, but there is definite slip - so no change from the fluid/filter change.

Any ideas? There was no mud IN the tranny, but I noticed there is still mud on the outside of the tranny - is there a breather vent or something else I am missing that could have gotten plugged with mud? Could the modulator be causing this?

 

Stich a hose on the modulator to create a vaccum, it it pulls and hodes, its working, if not, chage it, your troubles may be over..

 

vac or not, the modulator won't make slip, you could actually run with it disconnected, and the trans would simply act like you're driving at full throttle all the time. By removing the vacuum line, you are raising the pressure, which raises clamping force, that is why it will move when you remove the line. Sorry to say it, but it looks like the forward clutch is fried.

 

Thanks guys. I kinda think the tranny is fried, because last owner told me it was fine 'til he high centered the truck and got her stuck. Nothing looks bent or broke anywhere, but the fluid was low and dark like old motor oil. I'm thinking he worked the truck pretty hard to free it and got the tranny hot and a lot of fast R to D to R shifts.

I'll go ahead and test the modulator and start thinking about a tranny. I have a bunch of trucks, but no spare tranny. Is a C6 a C6? Meaning if I find a C6 from an old car, will it work? Or do I need to find one same range years (80-86) from a small block V8?

 

You will need one from a small block (302, 351W), unfortunately, not many cars used them. Most trucks and vans, however, did. Is your 2wd or 4? That does make a difference. The C6 is pretty common, so they aren't hard to come by. I had a short tail C6 in my 75 F250, and had a trans on hand from a 74 Galaxy, which was factory setup, and had come from a truck, since the prior owner had smoked the original. So yes, some cars will, but in the 70's, come 80 they were all smaller and wimpy, in comparison. Most cars at that point were using C4's and Aod's were just coming on the scene. My79 E150 had a c6 behind the 351W, as did my parent's.

 

It's 2-wheel drive. A friend has one priced right (free) but says it was off a 300 I6 so I assume that won't work

 

The one off the I-6 will indeed bolt up as it is the smallblock bellhousing pattern.

Everything should bolt right up...go grab it!

 

Cool. THX all! Hopefully I can get it rolling soon.

 

forgot to mention that...

 

Just talked to my buddy and the tranny can be mine. Came out of a mid 70's truck I6 as mentioned before. I've heard there are a couple different flywheels and torque convertors - any concerns there or just reuse mine? Also tailshaft lengths - any thing to look out for there.... is is this whole operation a simple bolt up?

Really appreciate all the info!

 

Just reuse your flywheel, it will bolt just fine, and is (hopefully) properly balanced to the engine you have. There were no tailshaft changes on the C6 short of the 4x4 vs. 2wd, the only differences. 2wd to 2wd is a direct swap, no changes. Main concern I can think of in regard to the converter, is be sure it is seated all the way into the pump. If you are getting it about installed, but just won't slide up to the block, be looking for a why, don't keep tightening, you will break something, likely the case. If all is lined up and good to go, it will slide all the way up to the block, no issue. The quick way to check the clearance, you should not be able to get a finger in behind the converter and the pump housing. The way to seat it is to spin it and push into the tranny, lightly rocking it up and down as you spin it. Also, the converter only bolts into the flywheel one way, and the studs have to go through the flexplate (flywheel) before it will pull up to the trans. A little tip: cut the heads off a couple bolts that are longer than the ones used to hold the trans, and use them as guide pins to line up the trans and the motor, and keep them long enough to be able to get them out once the trans is in place.

It's guys like you that make this site fun for me, I love to help out, and relay the tricks and tips that I have learned, and try to help avoid the mistakes I made. so, Thanks to you as well!!!!

 

Desperado

Will an 81 F150 six trany bolt up to a 302 sb??? I'm assuming that the six bellhousing won't bolt up, but would think the trany would be the same as any smallblock trany???

Thanks
rlangs58

 

The 300 six shares bell with 289,302, and 351 W