Rusty Bowtie
General Category => General Discussion - Intros => Topic started by: munch on November 15, 2014, 03:18:54 PM
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I am crusing at different speeds and let off the gas and get a thud that sounds like it is coming from the rear, like being kicked in the rear. Any idea?
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I would check the rear u-joint.
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When I got my 200r a few months ago I also got a new drive shift and u-joints. New trans mount as well.
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Munch
How are you controlling your TCC?
Moose
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This trans has an overdrive doesn't it? I think you could try to duplicate the thud in and out of overdrive. I think it may be related to your overdrive, or maybe I have no idea what I am talking about :)
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I had a van as a kid that started making a thud when I turned corners. Didn't know anything about cars so afraid something was gonna fall off took it to a front end shop and they replaced some bushings and stuff. But when I picked it up and turned out of the parking lot - sure enough: "Thud"
So I drove right back in and told the guy, "Man, this thing is still makin noise!". He opened up the passenger door and pulled out a loose oil can from under the seat. "There's your noise" he said, and walked away. Man did I feel like a dork! :)
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Kinda tough to give accurate info online...(but) check for loose leaf spring bolts, bad leaf bushings, cracked springs. (If using leaf springs of course). Are your driveline angles correct?
The Vettes use a snubber on top of the differential above the pinion so when it's torqued the bushing contacts the frame.
But - don't rule out a front end noise traveling to the back.
My 2 cents ::)
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I am going to put it on the lift thisorning and check it out.
I don't know what the TCC is.
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All seemed good with trans mount, u-joints, etc. I did turn the back wheel and observed the opposite wheel turn in the opposite direction. And when I reverse direction there is a definite lag before the wheels catch and a clank noise. Could this be the cause of my thud?
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Hmmmmm.....sounds like could be excessive pinion/ring gear gap?
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Rear wheels turning in opposite directions is an indication of an open (not posi rear). Also, I believe a certain amount of play or backlash, accompanied by a clunk, is expected when quckly reversing direction of the wheels off the ground. That's not to say you might not have excessive play. How far can you turn the wheel before it engages?
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I don't believe that you would hear the back lash in the rear end as it is under a load while the tires are on the ground and rotating. Are you running a leaf spring set up?
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Yes I have a leaf spring setup, but have a triangular four link waiting on coil over to go in.
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How are the bushings in the spring eyelets?
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The reverse in the rear wheels before it catches is minimal, don't think there is a problem there. I cannot tell anything about the bushings in the eyelets.
But when checking the new drive shaft and joints, I can grab the front of the shaft at the yoke and get about 1/4 to 3/8 play turning back and forth. Also I get a noise when it catches. Is this normal?
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Have you checked rear end for broken teeth on ring and pinion......Are your wheels lug nuts tight...Just a thought..
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Yes that's normal, what you are feeling is the back lash in the gears. I'm assuming you have the vehicle up on jack stands and no weight on the wheels.
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My GMC sierra does exa the hoist ctly that when its up on the hoist i thought that was normal
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Yes it is up on the lift.
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Munch, I think if there is nothing obvious when you inspect underneath the car and iyou still have that mush play from the rear with the driveshaft out, I think the next best thing to do is to inspect the ring and pinion and get a backlash reading with a dial indicator (I think 6 to 10 thousandths). I know it's a PITA, but if you don't think it's right and you have checked everything else.......
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What I get myself into!!!
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No, no, no! Munch, if this is the biggest problem you have with the car you are doing great. You know how this stuff is, you just have to figure it out. In a week or so you will be like :o duh, that was easy.
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Munch
The TCC is the torque converter lock up clutch. The 200R4 and 700R4 has a solenoid that is controlled by a 4th gear pressure switch . Depending on governor and line pressure the solenoid will command the torque converter clutch on or off so that it goes from a fluid coupling to a mechanical coupling between the engine and transmission. The idea behind it is to give you better fuel economy by limiting torque converter slippage. I have seen occasions where either the pressure switch or solenoid are not working properly and the converter will either lock or unlock at the wrong speed/pressure and cause a clunk in the drivetrain. There are a number of ways that the system is controlled on stock applications with the later versions being controlled by either the PCM or BCM depending on application. On earlier models it's usually controlled by a brake switch so that it automatically disengages when you hit the brake. Most guys, including me just hook it up to a toggle switch that allows you to turn in on and off when needed like when you are on the highway and turn it off completely when cruising around town. You can run a later transmission without having the TCC hooked up without a problem but with earlier transmissions you can cause internal damage to the transmission if you drive too long with the TCC unlocked at higher loads. If you look at Jef Lynches tech topic I believe that he has some info on the subject. This is most likely not your problem but its worth looking into.
Moose
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Thanks all.
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Munch...did you figure out the THUD problem??
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Thanks for asking, I went ahead and used the Bowler Tru-shift cable setup and after installation I did the WOT twice like the instruction said. This allows the cable to auto set up. I then took it for a ride and reported the problem with the thud.
A day or so later I went to start it and always do the WOT thing before starting the car, and I noticed the cable ratcheted again as if setting up. Apparently it had not set up correctly the first time. I took it out, it shifted good and no thud.
I had already talked to tech support and they had given me an adjustment I could use, but didn't need it.
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Munch, maybe I missed something in the thread or I am just not familiar with this transmission? What is the Bowler Tru-shift and WOT?
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Chopper I believe the WOT is wide open throttle.
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Oh, ok, I'm missing it I guess, but that's nothing new :o
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Wide open throttle is correct, here is the link for the Tru-Shift.
http://bowlertransmissions.com/p/64/tru-shift-throttle-correction-arm-system
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Thanks, Munch. I got a better grasp now. I was not familiar with the 700r4 so I had to do a little quick research. Now I see how it all works together........I like my 400 mechanical linkage ;D
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Chopper 526. Simple explanation these two GM transmissions.the 200r4 &700r4 There is a cable called a tv cable that goes from the transmission-to a bracket on the top rear of the engine.It is also tied into the fuel injection or the carburetor If not adjusted correctly it will not engage overdrive or will burn out the transmission.vette59jdwl
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Thanks, Vette, that's what I didn't understand. I didn't realize how the trans was tied in with the carburetor. I guess I'm still stuck in the 70's.
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yes and if your running a 700-r4 or 200-r4 along with a HOLLY carb, you also need a special bracket on the side of the carb that controls the pull angle of the trans cable.
Apparently there is a specific geometry needed to operate the cables, I am referring here to LOKAR CABLES used with holly carbs. If you do not use this bracket you most likely will burn out your trans. Street rodder mag wrote the first article I ever saw on it back in mid 90's... The bracket was made by ATI transmissions at that time.
You also have to go to W O T pull the trans cable and have it stick 3/16 " beyond the bracket and tighten the set screw in the stopper , otherwise you will be smoking the trans. There is one of those brackets on ebay now will post picture.
http://www.ebay.com/itm/181492362249?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
mike........................................... 8)
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I have worked with these transmissions for years and the best way (and as far as I'm concerned the only way) to properly adjust the TV cable is with the use of a pressure gauge. There are now a number of manufactures who market cable systems i.e. brackets and linkage for the OD transmissions but the one that I have always used is from Bowtie Overdrives. They have published extensive information on the subject based on the knowledge that they have gained from working with these transmissions over the years. If you want to read a comprehensive description about how the system works and how to set it up properly take a look at the 3 part post (links below) entitled TV101. If you have one of these OD transmissions it's well worth the read. The TCC lock up is also important on the early 700R4 and 2004R transmissions as they were subject to damage if the lock up system is not working properly. The later transmissions were redesigned and more oil was supplied to critical areas and the problem was eliminated. I believe that there is some information on that subject on Jef Lynches Tech topic.
Moose
Part1 (http://www.tvmadeez.com/article/index.php)
Part2 (http://www.tvmadeez.com/article/part2.php)
Part3 (http://www.tvmadeez.com/article/part3.php)
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Man, you guys are giving me a real education. I don't have one of these transmissions but I will read up on them now. I did see that the early ones are trouble. Thanks for the education, I will now prepare for the test.
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They can be a pain to get right a friend of mine lost three transmission before getting it right, He is now looking at putting fuel injection on his car and will have to change the linkage again.
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I guess I am a little too old school, after I lost the first one I would have put in a 350 or 400 ;D
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I'm using a 350c in my 32 it also has a lock up convertor