Hi all, I just recently installed a newly rebuilt engine in my truck. It's had some minor work done to it, bored .030 over, towing cam, 4 barrel intake and 600cfm carb. Before I broke the timing chain and rebuilt it all, my transmission worked fine, except for a bad torque converter. I just ran it with the torque converter switch unplugged. Well since I had the engine out I replaced the torque converter with a new one. My transmission is an A904. I reasoned that I don't really have a high performance engine, and that the converter style I had was a lock-up converter, so I ordered a low-stall lock-up converter (part #CR9L at Advance Auto.) Well put it all back together and took the truck for a trip around the block. Truck starts in 1st gear, shifts into 2nd, and then immediately revs, and drops into 3rd gear. It's like it skips 2nd gear, but it doesn't cause it shifts to 2nd for a second, and then immediately goes into 3rd.

Only a few things I've thought of when it comes to why this is happening, (bear in mind, no one's ever accused me of being smart)

Does the torque converter sense a certain amout of torque before locking up? If so, do I need a high-stall converter because the new engine is producing too much torque for the low-stall converter?

My Transmission fluid is full, so don't think that could be a problem.

Anyway ideas guys?

 

You are correct that you have improved engine performance but have not built a screamer that will overwhelm your drive train. LOL

First this sounds like a tranny/linkage problem and not a torque converter problem.

Torque converters have 3 functions:
1. They allow slippage so the engine can idle when the truck is stopped.
2. They allow smooth shifting under load by absorbing the shift shock hydraulically.
3. They multiply engine torque to an increasing extent as the trucks speed drops and the throttle opening is increased. This reduces shifting and makes the trans more responsive.

If you have a lock-up converter and are having problems with it, have you checked the part throttle unlock solenoid system, including the solenoid. Here again I do not believe this is converter related.

I would take it to a good tranny shop and have them test drive it. It is free at a good and honest shop.

 

This "part throttle unlock solenoid system, including the solenoid" does it have something to do with a vacuum hose(s). I've got two vacuum hose plug in ports on my carburetor, one if the timing is vacuum advanced, "timed vacuum" and the other one says it's the "manifold vacuum" for non-emissions controlled engine. Well, truck was emissions controlled, but I removed the smog-pump, and the new intake is non-egr. So all in all, does a vacuum problem possilby control the "part throttle unlock solenoid system, including the solenoid"?

 

No. The lock-up solenoid system is electrical. Under the drivers side hood spring there should be 4 relays in a row. The one closest to the driver is the one we are talking about.

 

Well, I checked all the relays, and everything seemed to be plugged in fine. But I do have another question: Would a vacuum line not being hooked up properly cause this problem. Because I'm lost when it comes to the vacuum line issue of this engine. The transmission worked completely fine before we rebuilt the engine, and didn't really mess with anything with the transmission at all to cause anything internal to go wrong to my knowledge. So would a vacuum problem cause this, and if so, where do I need to look to solve it?

 

Anyone interested in our automatic transmissions might find these 3 links interesting. As many questions as we get on our transmissions I would like to see the moderators add these links as a sticky. Maybe they could call it AUTOMATIC TRANSMISSION INFORMATION.

http://imperialclub.com/Repair/Lit/M...145/index.html
http://www.allpar.com/mopar/transmis...-tom-hand.html
http://www.allpar.com/mopar/transmis...queflites.html

This comment was taken from the 2nd link.

I've really never seen too many pre-1978 Torqueflites "wear out" or break that haven't been either misused or neglected. Probably the only major trouble I can think of relates to the 1978 and later model year lock-up converter 904's and 727's. The torque converter had a piston and friction disc inside it that locked the turbine solid to the impeller front cover. This in effect eliminated any slippage in the converter and helped fuel efficiency. (The lock-up only happens after the 2-3 shift.) A few of the early complaints with the lock-up units were sluggish vehicle performance, pinging, bad cold weather performance, dying in reverse and most of all, vibration and surging after lock up. Diagnosis showed some units were locking too early and dragging the engine down (restricted cooler lines or worn oil pump drive gears sometimes caused the converter clutch to lock in reverse which killed the engine). The fix for premature lock-up was to install a different spring in the valve body to raise the lock-up speed. The pump clearances were also tightened to make sure ample fluid was available to keep the converter operating properly and prevent lock-up in the wrong gears. The lock-up Torqueflites probably caused more headaches for service technicians than any other previous units.

 

hey i had the same problem in my 99 dodge. I know you have an earlier model, but do you have a cable that connects from your throttle linkage to your transmission? if its sticky it will trick your transmission into shifting to 3rd too early.

 

Actually, the problem with mine was that since I installed an aftermarket carburetor, the shift linkage and the slide that it slid on didn't push the shift rod back enough, so I had to adjust it. Thanks for your help though.