Well, here we go. I'll try to lay as much necessary detail into this first post as to what I have done so there is a better basis to work from.

I own a 1986 F350 with a 6.9 IDI N/A that was wrecked 20+ years ago, so it now has a 1994 front clip and bed. The motor has never been rebuilt and I was told that the transmission hasn't ever had extensive work done.

After the splines inside the torque converter all sheared off and smooth, I began a rebuild of the transmission since I had to take it out anyway. Side question: Torque converter was forest green with no markings, was this stock?

The parts slowly started to arrive in the mail and the rebuild began. Raybestos HP clutches, Kolene steel plates, upgraded E-Ration servo apply lever, kevlar band, new washers, new rear sprag, bushings, S code servo, new filter, etc. I also installed a Transgo shift kit in the valve body and of course a new torque converter.

After slapping it all together, I fired it up and let it warm up for a about 15 min as it was the first time I fired it up in 3 months (rebuild didn't start right after it broke down). After double checking fluid levels (Valvolene Dex/Merc Fluid), the first get up and go felt great as it cycled through all 3 gears. I only drove to the end of the street then threw it in reverse and that also felt very strong.

The next morning i took it for a true ride to test it out. Again, all three gears automatically shifted great, although for having a shift kit and upgraded band apply levers and such, it didn't feel much different from prior to the breakdown. On the second acceleration from a stop, i noticed that it didn't feel like I started in first, or certainly didn't have a distinct shift from first to second.

This has been the common theme for the last week. The first acceleration up to highway speed of every day is flawless, albeit not the pulling power or strong shifting i thought I should get (but i'm not too experienced in the power of these older diesels so maybe I dont know?). Here is where it gets wierd: Reverse is the same. If I put it in reverse with the fluid still cold first drive of the day it has tons of power in reverse and shoots backward. Once the fluid has warmed up a touch, reverse will easily get to 3000rpm with no power and only be going a couple mph in reverse. And once the fluid has warmed up, it seems I start out in second gear (or first with so much slipping into second that I dont notice) and with slightly slipping shifts going from 2nd to third at 2500rpm @ 40mph.

Yesterday I verified that the 2nd band adjustment is correct per the book, the vacuum at idle is 16in @ the module, and I dropped the transfer case to pull the governor and clean it again. When I dropped the transfer case, i noticed the fluid was very dark. Definately not what it should be with only 200miles on it after a complete rebuild (once in third it cruises great). It did not smell burnt but my head wanted to think there was a hint of smell?

The only thing I can think of is that I didn't flush the cooling lines
and maybe something got stuck in a line or something when the torque converter went out and the fluid is not cycling properyor it is simply the old fluid that got cycled in with the new fluid and that is the cause for the discoloration.

I plan to change the filter, fluid, and flush the lines in the coming days, and maybe i did something wrong when installing the transgo kit and the line pressure is off (but shifts properly when cold?) but other than that, any other thoughts?! I researched fluid before my rebuild and seemed everyone was suggesting the Dex/Merc but maybe that is bad?

Thanks for reading my novel, but i wanted to present the whole story.

 

You may need to mess with the gizmo on the throttle linkage at the injection pump. This is another Ford rigging, with a engineering stamp on it.

The c6 was made for gas engines, not diesels. So it uses the governor in the trans(road speed) and the load on the engine(engine vacuum) to decide when to shift. But guess what, a diesel does not have vacuum.

So they decided to take the vacuum they do have from the belt driven pump, direct this up to a plastic piece on the throttle under the aircleaner. You will see the vacuum lines. This plastic piece varies the vacuum depending on the throttle position. It will have a vacuum line from the supply, and another one leaving and going down the backbone of the trans to the modulator. This plastic piece varies the amount of vacuum to the tranny modulator depending on how much the throttle is opened. They have been known to go bad or be out of adjustment.

More throttle means less vacuum. Less vacuum means a harder later shift. Lots of vacuum means not much throttle, so a early soft shift. On this setup you can mess with the thing on the throttle, and you can adjust the modulator like you would on a regular gas setup. So they will interact with each other somewhat.

 

Very good thought. I think you are referring to the Vacuum Regulator Valve? I just read the procedure, and it looks like i need to get my hands on a manual vacuum pump and then i'll set it per the book. Thanks for the input. I'll report back in the coming days after i have done this.

 

It has been a few days, but I want to update this post and ask other opinions.

I have verified the VRV is adjusted per spec. Good thing too since those philips head screws look like they may never want to move. haha

I dropped the pan, flushed the cooling lines, and changed the filter. Good thing too because I found all the crap from when the torque converter splines crapped out. All the junk must have been in the cooling lines. The filter was so dirty i'm not sure fluid was passing through at all.

Anyway, after the fluid swap, it was like a whole new truck. Great power at every start, even after it was warmed up, which it was not doing before.

BUT, still no power in reverse. There is a very distinct 'thunk' when shifting into reverse, and without throttle it will roll itself backward, but any throttle applied just revs up the motor, rather than sending the power to the wheels.

The interesting thing is that when I had first completed the rebuild on the transmission, I did run it in reverse and it had great power. My best guess is that some crap that was in the cooling lines got shot up into the valve body and was messing with me. The forward gears now work after a fluid and filter change. Maybe something is clogged in the valve body for Reverse? I'm not 100% sure, but i'm guessing there has to be a reverse passage inside that valve body, right?

Thanks for the help!

 

That's why you really can't do surgery on a automatic trans. When something goes it sends metal all through everything. I think you are going to have to pull it out, go through the whole thing again and clean everything up.

I had a torque convertor go on a c4. Changed it out and put it back together, and it would hesitate in reverse and make a buzzing noise. Someone told me there is a piece of trash somewhere up in there that was causing the problem.

I am a cheap skate, so when I was looking to get a tranny rebuilt I went down to the local trans shop and asked them how much it would cost. I then asked how much it would cost if I pulled it myself and brought it to them. It would have only saved me $100 and they said they would not guarantee the trans. I said "why not" and they said they properly clean the cooler in the radiator before they hook the new trans up, to get all the debris out from the old trans. If they didn't clean it, they are not guaranteeing the rebuilt trans, too much risk from dirt getting in it and messing it up.

 

I installed the SK6 transgo shift kit with the Stage 2 spring. Does anybody recall how many check ***** go into this valve body? When i rebuilt the valve body, i recall taking one of the THREE ***** out and replacing with a funnel shaped piece from the kit.

Does that sound correct? 2 check ***** and one replaced with a transgo piece?

 

I believe you are correct, 3 ***** originally.

http://www.fordification.com/library...geViewsIndex=1

 

Thanks for the help Franklin2. Since the truck works tremendously in forward and reverse when the fluid is cold, i'm going to have the system flushed and probably install a new valve body from Broader.

Obviously trying anything so i dont have to drop the transmission again. haha

 

I have now narrowed the problem down even further. When the fluid is cold, reverse and drive (automatically shifting through all gears) work flawlessly.

Once the fluid has warmed up a bit, reverse has no power and just winds up the motor with any throttle. It may shudder a tad? Also, while MUCH improved from before the pan dump, filter change, and cooling line flush, the automatic shifting still is not as positive as it is when the fluid is cold.

Maybe that will generate some new thoughts?

 

Something is leaking by or does not have the proper pressure. Like the oil pump. The transmission works on oil pressure. When the oil is cold it's thicker, so it generates more pressure. When the oil warms up it's thinner, and if there is a leak somewhere it's easier for the thinner oil to escape through there and avoid doing it's job in the transmission.

It's going to have to be pulled again I believe.

 

Thanks! I appreciate your help Franklin2!

 

I don't know that it is mandatory, but a lot f guys install an inline filter into the return line after rebuilding a tranny. Gives a little more insurance that the new fluid wont break some crud down and send it through.

 

Good idea! I'll have to do that next time.

 

I know some of the online aftermarket rebuilders that ship rebuilt trannies REQUIRE a filter be installed or they will not warranty their trannies. They usually ship one with the trans.

 

I ordered a spin on type setup to be placed in the return line from the cooler. I'm worried that with the amount of contaminant left in the fluid, a flow through style could possibly clog too quickly. I'll run a filter for a hundred miles or so then swap it out. I'll run a second filter for about 200 miles or so and at that point i'll change that spin on filter, drop the pan, swap out the C6 filter and rebuild/clean the valve body. This will be my last gasp attempt before the inevitable complete rebuild again. I'll post up results to finish off the thread.