1970 Roadrunner 727 Problem.

[TimS]

Buying a #'s matching 70 Roadrunner from a buddy of mine this weekend. Drive line has been rebuilt by a previous owner but the 727, at take of, will not move the car for about 15 seconds or so, (forward or reverse). It will go at that point. I haven't had the car out on the road to see if it will shift properly other wise. Talked to the previous owner a couple of nights ago and the tranny does this with warm or cold fluid and has performed this way since the rebuild. Any help would be greatly appreciated.

 

[BeepBeepRR]

Torque converter might be the issue. Also fluid level,band adjustment or could be pump pressure adjustment too. You can google that adjustment. I'm no trans expert just thoughts off the top of my head. Also how large of a stall converter is it?

http://www.hotrod.com/articles/15-tips-improve-727-torqueflite-trans/



This is a truck but the idea is the same.
https://www.dieseltruckresource.com...bands-shift-points-line-pressure-pics-265745/

 

[TimS]

I believe a stock size converter. I'll check on that. I wondered about it being just a pump pressure adjustment also. Talked to the local tranny shop and they mentioned inner seal issues as well. Thanks.

 

[dvw]

Start the engine. Let it run in neutral. Then try it. My bet is your problem will be gone. The torque converter drains back while parked. The 727 doesn't pump fluid into the converter in Park. Only in neutral or in gear.
Doug
Read here;
https://auto.howstuffworks.com/auto-parts/towing/towing-capacity/information/torque-converter2.htm

 

[PurpleBeeper]

I'm no expert either, but beepbeeprr has some good ideas. Check the fluid level & maybe change the filter first thing in my opinion.

 

[AR67GTX]

Yes, need to know if this is happening after the engine has been off a little bit. The pump does work in park but the pressure is shuttled off elsewhere and filling the converter is very slow. Put the transmission in neutral and full pressure/flow is directed to the converter.

 

[dvw]

Torque converter might be the issue. Also fluid level,band adjustment or could be pump pressure adjustment too. You can google that adjustment. I'm no trans expert just thoughts off the top of my head. Also how large of a stall converter is it?

http://www.hotrod.com/articles/15-tips-improve-727-torqueflite-trans/



This is a truck but the idea is the same.
https://www.dieseltruckresource.com...bands-shift-points-line-pressure-pics-265745/

Fluid check is always the 1st step. That being said band adjustment has nothing to do with not moving cold. 1st gear uses the low/reverse band for low gear braking only. It is used in reverse but would not effect forward. The intermediate band is applied in 2nd gear only. A partially plugged filter? Maybe, but that usually shows up hot, not after sitting.
Doug

 

[BeepBeepRR]

Fluid check is always the 1st step. That being said band adjustment has nothing to do with not moving cold. 1st gear uses the low/reverse band for low gear braking only. It is used in reverse but would not effect forward. The intermediate band is applied in 2nd gear only. A partially plugged filter? Maybe, but that usually shows up hot, not after sitting.
Doug

Right on.. Just offering suggestions.. But I actually think the neutral deal might be the issue as other have stated. I forgot about that.

 

[Trashdog67]

The first thing I would check is the throttle kickdown linkage adjustment. If it ain't right it will act just like you described. Not good for the tranny to operate like that.

 

[oldbee]

Gotta go w/Doug, converter drain back. Reverse shud take longer also because pressure is about 3x higher than forward.

 

[J5 GTX]

You can check Line Pressure easily on a Torqueflite. There is a plug on the side of the case. Install a fitting and you can run a hose and gauge inside the car. Not saying you have a line pressure problem but, it might provide some clues. I recommend checking it anyway after a rebuild.

 

[TimS]

Start the engine. Let it run in neutral. Then try it. My bet is your problem will be gone. The torque converter drains back while parked. The 727 doesn't pump fluid into the converter in Park. Only in neutral or in gear.
Doug
Read here;
https://auto.howstuffworks.com/auto-parts/towing/towing-capacity/information/torque-converter2.htm

Did all that. Allowed the fluid to warm up and ensured the fluid was at the correct level. Still will not pull, even load the motor, initially. Will work in Reverse.

I did find out that it has a rebuilt stock size converter in it from Dynamic converter in Melrose Park, Illinois.

 

[TimS]

Gotta go w/Doug, converter drain back. Reverse shud take longer also because pressure is about 3x higher than forward.

Juts played around with that this morning, cold and warm. Cold, it would move in reverse at the hit. Hold the brakes and it will load the motor. Will not do this in "Drive". No load and just sits for about 15 seconds or so then it will gradually move.

 

[wannadrag]

Converter drain back,they all do it. Neutral for a few seconds and your good to go

 

[oldbee]

Juts played around with that this morning, cold and warm. Cold, it would move in reverse at the hit. Hold the brakes and it will load the motor. Will not do this in "Drive". No load and just sits for about 15 seconds or so then it will gradually move.

Define “gradually” please. At an idle or above that. Even when hot mine will delay it on a hill(nose high) if Parker after 1/2hr or so. If you have to rev up to get moving forward, you may have other problems.

 

[TimS]

Define “gradually” please. At an idle or above that. Even when hot mine will delay it on a hill(nose high) if Parker after 1/2hr or so. If you have to rev up to get moving forward, you may have other problems.

I do have to rev up to get moving in drive. Reverse you don't have to do that. Put in reverse and it moves backward w/o touching the accelerator. Drive: you can't even feel a load on the motor at all then after the 15 seconds or so it will gradually begin. I've had lots of Muscle Mopars over the years. This isn't normal for any Automatic.

 

[dvw]

Did all that. Allowed the fluid to warm up and ensured the fluid was at the correct level. Still will not pull, even load the motor, initially. Will work in Reverse.

I did find out that it has a rebuilt stock size converter in it from Dynamic converter in Melrose Park, Illinois.

OK next step. If it moves in reverse only I suspect a problem with the rear (direct) clutch. It is the only component that has to function for all forward gears but not reverse. Throttle pressure linkage has noting to do with engagement either, though if wrong could have caused damage.
Doug

 

[mopar 3 B]

Have you tried starting by manually putting it in 1st?
Some one install a manual valve body? If they have in D the trans will try to move the car from a dead stop in 3rd gear. It takes some rpms to get the converter to speed.

 

[TimS]

Have you tried starting by manually putting it in 1st?
Some one install a manual valve body? If they have in D the trans will try to move the car from a dead stop in 3rd gear. It takes some rpms to get the converter to speed.

Yes have tried that. Same result as in Drive.

 

[mopar 3 B]

Time for line pressure test and possible an air pressure test of band servos and clutch packs.
Does the po know what was included in the trans rebuild?