Engine/Transmission (1994 - 1998) 47RH transmission control

[Howard Durand]

I just returned from a trip to western Nebraska, towing our 29' TT which weighs in at around 7000#.

It was a new experience and I am not real pleased with the performance of the truck and transmission.



The greatest problem is with transmission TC lockup timing.

The PCM insists on locking up at around 45 mph, right after OD is enganged. This is way too soon and the truck starts bucking and I hear noises like two pieces of metal grating together which I assume is TC slippage.

If I keep the TC unlocked until after the OD engages, and I have a speed of about 55 mph, I can then let the TC engage and everything works real well.

Since this was not a problem last year, when I was using the Banks plate, I am wondering if the TST #5 plate is just not right for this truck or if it is not installed correctly.

With the Banks plate, even though TC lockup was happening too soon, the truck would get under it and begin picking up speed. EGT would climb rapidly and I would usually have to get out of lockup but it never bucked and slipped like this time.



The two mods that have been done since last year are the #5 plate and 3K GSK.

I would think that the #5 plate would provide better fueling and let me accelerate after lockup without the bucking and jumping that causes the slippage.

As it is I keep the TC unlocked until I get above 50 mph.



Is the #5 plate and the GSK a bad combination? Or could it be the governor lever needs to be adjusted?



No matter what, I am going to try to come up with a scheme that will hold the TC out until a set vehicle speed is reached.

 

[Joe G.]

Howard,



I had to adjust my TPS before mine would work correctly when I was towing my TT. That required that I remove the sleeves around the TPS mounting screws and file the holes a little to get the voltage right. I let mine run with the switch in normal (PCM controlled) mode until it gets up to the speed I want to run at. Then I lock it up so that I have the exhaust brake available when I want it. Some situations I force the TCC to stay unlocked. White Bird grade in ID is a good example. With the #5 plate you have enuff torque to slip the TCC with that old BD valve body for sure. I can slip my TCC on hard pulls. The forced unlock keeps my EGT under control better. My TC is very efficient unlocked so I don't loose much with it unlocked.

 

[y-knot]

Can not you just leave the OD in the off position until the right speed has been reached???? Then just reach over and push the button to engage the OD, works for me.

You only tow 7000lbs, so your trany will last a while longer then mine did, but if you continue to tow you will be soon enough looking for a aftermarket replacement. Stock Dodge auto's are tough, but not truck tough. And the TC's are junk, most can get one to slip with stock HP .

 

[Howard Durand]

I tried both ways, manually operate OD and let the TC operate normally or let OD work normally and manually control the TC.

Controlling the TC worked best for me during the trip because I wanted to get up to freeway speed in OD before locking up.

I figure that saves unnecessary switching of the TC.



I am not using the stock TC, it was replaced several years ago with one of the early BD low stall converters. I also have a BD enhanced valve body.

I am thinking my problem is in the fueling curve. I think I need to get fuel a little earlier in the acceleration process. Even though I have tinkered with the AFC, I am thinking the governor lever may need to be raised just a bit to strike the plate at or above the nose. I think it is hitting a little low.

I won't be able to tell for sure until I take a bunch of junk off the engine so I can see it.

I intend to give both Piers and Bill at DTT a call and ask for some help.

If things don't get better soon, I think I can convince myself that I need a rebuild.

 

[Joe G.]

He has a 47RH with a modified VB and TC. I had that same BD VB once and had some problems like that. I managed to get it to work better with adjusting the TPS. Not a lot better, but better. The old BD TCs were a milled stator type. I would think that would reduce TC life span so it might be giving up. The governor might not be working right. I had that problem once too. I had to change a valve in the fly weight part. Another difference between the RH and the RE is that the RH has a three land switch valve and the RE has four. This affects how the lockup works. So if pressure is down a bit that might cause what is happening.

 

[tgrfan2]

The 'puter on my 95 is dead and allows lockup around 1200 rpm which makes it a bucking bronco. I put a toggle switch in per the TST website which allows me to delay lockup in drive or OD. Works pretty well the last 90K.

 

[Howard Durand]

The "switch" was a lifesaver for me, otherwise we would have been stuck somewhere with a shredded torque converter or driving with OD off all of the time.

The problem is, I have a semi-automatic transmission now and would like to have something I don't have to mess with.



Joe, I believe you are right about the older BD TC. They have been proven to be inadequate compared to the improved ones available now.

I bought mine in 1998 following a glowing article in the TDR. I think their praise was a bit premature.

It cost me a bundle to buy the TC and have it installed then I find out later that a much more rugged and reliable design is available.

An expensive lesson in not believing everything you read.

I now take with a large grain of salt the glowing descriptions of any new products.

 

[GHansen]

Try stretching the spring in the over flow valve- worked for me...