I have a new engine in the car and since I installed it this has been happening. It makes it very difficult to break the engine in because I'm afraid I might tear something up in the drivetrain. Here's what happens: when in OD and the converter locked up at 50mph or so I will start to slow down for a red light, around 2200 rpm the car starts to jerk and I can hear a whine from the trans tunnel while it is jerking. It stops doing it around 1700 rpm and smooths out. I mind you that the converter is locked up the entire decel coast distance and unlocks at about 1100 rpm just before coming to a stop. My question is does this sound like a trans problem (i.e. converter) or engine tuning? The engine is new, heres what I got: 10.5:1 332 cu in, .550 lift 240@.050 cam, 190cc alum heads, victor jr., and speed demon 750 carb. I appreciate any input. Thanks!!

 

Are you talking about an actual delay in the downshift or does it just shudder when you start to decelerate?

U sure your converter/conv clutch is working?

 

sounds like a bad TCC solenoid, definately not engine related

 

Torque converter lockup is hydaraulic, not electrically controlled any more. It is definately a jerk, and very spuratic its in no kind of way rythmic. All my friends are boggled by this too. Has any one ever heard of an engine that just has bad harmonics at certain rpm's? Keep the ideas coming!! thanks

 

I would think that if the engine had bad harmonics, the jerking or shuddering WOULD be rythmic. If the torque converter is hydraulic (not sure how that setup is) then i dont think that would be the problem. But there are so many parts that can get jammed in an auto tranny...if you're shifting up fine but wont go down smoothly then it may be the return spring in the servo...or something as small as a ball bearing in the 3rd accumulator retainer getting stuck. I'm trying to diagnose my A4 right now and have its insides spewed across my work bench so i might not know much more than the next guy. Im tempted to toss the A4 and get a T5.

 

Orlando, I'm with you on the T-5 or T-56 swap, thing is finding the parts then buying them. What I mean by my converter being hydraulic, is that the clutch lock up isn't acutated by an electric solenoid, but manually within the valve body of the trans. Its the older style of converter clutch lockup, my car isn't fuel injected it has a carb. When I pulled te ecm, the converter didn't lockup any more.

 

Shot in the dark, but I've experienced a similar problem with 2 separate stock LG4's after bumping up the timing. In each case the car would SLIGHTLY hesitate or shudder when decelerating with converter locked (in all gears). Not violent or anything, just enough to notice. In each case dropping the timing back down resolved the issue. Most likely not the case for you but it would be easy to check.

 

Sounds like you need more stall speed. That's a rather stout shaft and compression. Need at least 2800 mabe 3000 stall and 3.70 gear. If the drive train is not relaxed when you let up on it the cam will try to lope and act like too much clutch-not enough gas. That should be a bada** lil motor from the specs you gave.

 

MrBrooks is probably closest but more stall won't come into play when the TC is locked. Don't know how you're controlling lock up but releasing it at higher speed or engaging in fourth gear only would help. I've seen the toggle switch mod...

 

You're rite naf,the tc being locked is the root problem. Unless the car is a daily driver I would not even run a lockup type(but i'm old skool like that). That setup still needs some stall and gear tho.

 

Or a switched disconnect so it can still be engaged on those long freeway cruises.

 

Well my trans guy told me in order to keep from burning up a converter I needed to change the valve body in the trans to allow for manual/hydraulic converter lockup, I think it works off of line pressure and TV cable. So here's another question: Should I just change the converter out to a non-lockup and higher stall? By doing this will the valve body configuration need to be modified so that it doesn't try and send lockup pressure to the converter when there's no clutch to lock up? I like the idea of the manual switch as well though, Mr Brooks I think your right in regards to alot cam and compression and the engine trying to lope when there's no "room" for it to do so. Mr Brooks what would you think my "lil setup" put down to the rear wheels on the chassis dyno? I'll let you know I made the pulls in second gear, b/c the trans kept trying to downshift from thrid to second under full throttle. That issue is fixed now.

 

More stall will also generate more heat, all else being equal. When the rpm's are below the stall speed the verter slips more. Heat is, of course, bad.

Not sure what your trans guy did. How does it unlock when you brake?

 

I understand that when fluid is sheared heat is generated. It unlocks around 1000 rpm just before you come to a stop.But the way I have been driving is as I decel I put the car in neutral and just before I stop i put it back into drive. This thing needs more converter I relize that, but should I run a lockup or non-lockup at this point. If anyone on this board builds trans for a living, they know what has been done to my valve body to make the converter lockup manually and not electrically.

 

BTW, thanks guys for all the input, help, and suggestions!! I don't play around on the forums much but this has been very helpful!!

 

You can purchase a kit, or install the appropriate vacuum switches yourself, to retain the electric lockup without the computer. This keeps the lock up running through the brake pedal switch and would allow you to install a disconnect switch in the circuit. At this point you're probably best talking to the guy that modified your trans to decide which way to go.

 

Naf, are you saying that the converter lockup/unlock is dictated by the brake pedal position? If this is so then the converter should be unlocking when I apply the brakes; correct?

 

The electrical circuit that normally powers the lockup solenoid is run through a switch that cuts power to it when the brake pedal is depressed. This does release lock up when the brakes are applied. Don't know what you've got now.

 

It sounds like torque converter shutter, (casued buy what?)

Unlikely, but possibly a cracked or loose flex plate for the noise.

 

I should think 300-325hp my be a conservitive number at the ground. Smaller morort when built properly will make great high rpm hp and be a lil bit shy on tq especialy down low. What did ya get???
Give the guys at PTC a call. These guys know what they're doing when it comes to torque converters. They will want to know EVERYTHING about your setup and then build you a converter that is EXACTLY what you need. We have used them in everything from street cars to outlaw 10.5 cars with NO problems. If they can build one to take 4.3 second 1/8 passes at 180mph they know something.
http://www.ptcrace.com/

 

Well Mr. Brooks, it put down 230 hp 242 lb ft torque. Needless to say I'm completely disappointed with those numbers but oh well its fun to drive and feels like alot more. Guys I appreciate all the help on this subject matter. But I talked to my tranny shop today and the I'm dropping the car off next week to let him figure it out. I'll post what he tells me and what I end up doing. More than likely it'll get a bigger converter and manual lockup switch.
Thanks again!!

 

I would have to say the 750 carb is a bit big for that combo.
Just look at the Torque Number...

 

If it's a hydraulic lockup kit installed, the spring rate may be off...

If it is still elect. lockup, i'm with naf...your brakelight switch has two sides to it...one to turn on the brake lights, the other to turn OFF the elects to the torque converter. Could possibly be the TCC solinoid too...if it has trash in it, it needs to be replaced. Easy as pulling the pan and removing two bolts, splicing two wires...done.

Good luck, let us know what the tranny shop said...