Hey guys, I rebuilt the C6 in my 1979 F150 last year. I rebuilt the trans as part of a frame up refresh with some suspension mods. When I lost 3rd and reverse, I decided to take the entire truck apart and address all the various issues.

This was my first automatic transmission overhaul attempt. The clutches, gears and band in the case seemed pretty understandable. The valve body, on the other hand, seemed mysterious due to the row of shuttle valves and labernith passages.

Needless to say, I was waiting for this day! This week I finally got the cab back on and assembled. I went out and bought a battery, lit it off and filled the transmission with oil. At first the transmission had no gears at all! But when I shifted the transfer case out of neutral, things got better!

But not great. I'm not ready to drive it yet, as I don't have the doors, fenders, hood or bed back on yet. But I did move it forwards and backwards a few feet in my work space. What I found was that reverse seemed fine. "D" and "2" moved the truck but felt as if it were binding. The biggest issue is that "low" was also reverse!

I need to hear from you guys on possible tests and remedies. I'm thinking one of the spool valves in the valve body is pooched. but then again, I'm lacking troubleshooting experience on these. I hope this brief explanation will give you enough information to help me out!

Thanks guys,
Rick

 

About the valve body: Don't mess with it! Clean the gasket material off but put the check-***** and stuff back exactly where they came from. If doing a shift kit, go through each valve/spring one at a time and put each one back before moving on to the next one. Make sure no dirt, sand, gasket material, etc is gunking up the valve body halves before putting it back together. Keep your work area clean! If you messed with the valve body, all bets are off.

IMHO, the only thing you can do now is to remove the whole thing, take it completely apart, and follow the assembly guide again. You did use a diagram on how to put it back together, right? You didn't just try to go off of memory, right?


You should find a diagram like this to use as a guide.

 

I will also be tackling my first C6 rebuild soon - full rebuild with 4R100 forward planetaries, etc. I hope to avoid any major issues myself!

 

SDDL-UP... you may already have your tranny build all done but thought I'd throw this in just in case. I took a lot of pictures, I mean a lot! I also found a clean spot in the shop I could lay out each piece in order as I removed it.


The C6 was only the second tranny rebuild for me and things went well. Good luck on your project.

 

Thanks fuzzybob! I will report back, still gathering parts right now. I like the idea of having the LARGE work area and drop cloth too. I have heard of people putting the case in a bucket for reassembly. How did you reassemble yours?

 

sddl-up, start a new thread so we don't hi-jack the OP's post. I've got pics.

 

When I rebuilt mine, I used an old kitchen table as the work surface. For re-assembly, I used a 7 gallon metal bucket (from farm store) with a couple of 2x6 boards on top in a V pattern. This allowed me to set the transmission on the tail (without the tail housing) to support the weight of the transmission while re-assembling the components. The output shaft stuck down into the bucket and any fluids would also be contained too.

 

Since you should rinse the governor and check it's valves for free movement I would leave the governor off the output shaft until you have the front pump installed and are ready to install the tail housing.
No point in risking crushing the governor housing!!!
Trans shops just drill a hole in the drain tables. One of these days I will get my own drain table. They are so great for sloppy work. I think used restaurant equipment places might sell smaller versions.
When doing side jobs I had an old leaf type kitchen table and would spread it a couple of inches to let the main shaft stick down thru.