Here's one for you transmission experts out there. I was having some trouble a few weeks ago with shifts from 2nd to 3rd after pulling a heavy load with the OEM trans cooler. I called Brian at BTS and he thought just cleaning the acumulator valve would solve the problem, so I dropped the valve body and replaced all the valves since they were fairly cheap. While I was there I also put in a Transgo reprogramming kit, and added a 6.0 trans cooler. Put it all together and everything seemed to work great, good solid shifts, no leaks.

So here's the question. I drove about 70 miles the other day(first long trip since I did the work) to pick up camper and boat out of storage for the season. Pulling a load for the first time, the TC didn't seem to want to engage from a stop when the "Overdrive OFF" button was not pushed. When I pushed the "OFF" button (light on) the trans engaged as normal, then I could push it again (light off) and the trans would shift normally. Now (after dropping off the load) it's working as normal. Load wasn't really that heavy, camper weighs about 3000#, boat on trailer about 4300#.

Any one have any idea what I'm dealing with. Can't really afford a new trans, but don't want to get stuck somewhere this summer with a camper and boat.

Sorry for the long post but wanted to be clear. BTW I have checked the fluid level quite a few times and it has been full except I added about 1/2 quart after this trip. Used Mercon, not Mercon V.

Thanks for any insight or suggestions.

 

Im confused. If he TC didn't do it's thing at a stop, the truck wouldve stalled. This is more of a bump than anything, but in all honesty your post is kind of confusing.

 

I think he's saying it didn't lock until he cycled the OD switch...

 

I think he is saying that the overdrive one way clutch didn't engage once. If that is what happened it will do it more and more until it never engages.

 

Sorry I was away for a couple days. I don't really know the proper terms for what seems to be happening, but what I think I experienced was the transmission not engaging normally under a load. It seemed to slip, or not connect as if I had the shift lever in N instead of D, but if I hit the OFF button on the shift lever it did engage. I've been driving without a load and everything is operating normally. If it is the coast clutch(?) how would I test for this and is something I can repair if it is going bad?

 

Correction "OD One way clutch" not coast clutch. I've never heard of this clutch.

 

If I am not mistaken, the OD off button simply prevents the trans from switching into OD. Nothing else. On later models, it was replaced with a "Tow Mode" switch. I am under the impression that those changed the shift schedule for towing.
In short, I don't see how one could have anything to do with the other. Not denying what you saw, but could it be coincidence? When you put your truck in gear, it should be immediately routing fluid through the "Low clutch" (I believe). Your TC is spinning because of fluid being pumped through it and it "grabs" when the rpm climbs past the stall speed.
It sounds to me like your trans did not shift. Check the electrical connections on the shift switch and check the switch. Presumable it was removed when you had the trans out and could have cracked or made a bad contact during reinstallation.
Just make sure you chock your truck if you remove the switch. (Cost me a hospital visit, it was ugly)

 

Thanks for the suggestions. I didn't remove the trans to do the work I did to it, simply drained it, removed the pan, filter, an the valve body, did the work on the bench, then reversed the proceedure, all on a creeper. So didn't have to disconnect any eletrics. I agree with you the OD off switch shouldn't be related to the TC from what I understand about them. I was 70 miles from home when this occured and kind of freaked when the trans seemed to be slipping from a stop and just tried anything to get home. Hitting the OD off seemed to make a difference. I'm looking for a way to test to see if I actually have something going bad, or was this simply an anomaly? When I did this work, I drained the TC because I had heated the fluid pretty good when towing with the old cooler. Could it be possible the TC wasn't completely full of fluid (bubble perhaps?) and the long trip under load worked the bubble out? I did add about 3/4 quart Mercon after this trip.

 

Sounds possible. I have a theory that dates back to when I was a Apache Crewchief. "Always start where you last screwed with it". I have gotten myself out of so many pointless jobs with that one.
BTW if you trans is slipping, your OD light should start blinking. There are sensors on the front and back of the trans. Their readings are compared by the computer and will flash the light if it suspects slippage.

 

That had happened to me before I put in the 6.0 cooler. The weird thing is it didn't flash in this case, so probably didn't throw a code. Don't have an AE so can't check. Should get one but money's tight.

 

You're mistaken.

Turning off the OD turns on the coast clutch. The coast clutch holds the same way that the overdrive one way clutch holds when accelerating. If the overdrive one way isn't working and the coast clutch is applied the truck will move. This pretty much confirms that the overdrive one way clutch has had a problem.

To fix it one would remove the trans, remove the torque converter and the pump, then the overdrive gearset and clutch. Since the trans is now about 2/3 disassembled, it's probably worth rebuilding it.

 

Is this serious problem? why does the trans seem to work OK now? Is this something I can test for? Is this something caused from the Transgo mod? and can I go back and fix it? Should I just find the money and buy a new trans? Should I save up more and buy a BTS or JW? Can I wait that long? Need this truck for what little work there is. If turning off the OD and turning on the coast clutch fixes the problem, should I expect more problems down the road? I didn't have a problem with dropping and working on the accumulator valve body, but a whole trans seems a little out of my range of comfort, and time frame.

 

If it works now you probably have some time. Turning the OD off below 30 MPH will buy you more time. I expect that eventually the one way clutch will die and then OD will have to be off to get it to move.

The trans has to come out and be at least partially torn down to change the one way clutch.

 

Thanks Mark,
Just drove home and it's starting to slip pretty bad. Is changing the one way clutch too much for a good shade tree mechanic? The only other option for me is the dealership, they want $4300 for a new one. Does anyone know of a write-up for this? Don't mind dropping the trans in the driveway if it's something I can do myself. Any one know of sources for parts and what parts I'll need?

 

Are you comfortable with taking apart an automatic? There are some good shop manuals that can help. ASTG has one, Helm, Inc, sells the Ford manual.