I know that there have been posts before about getting knock only when the tires break loose...... false knock, or real knock? Has anybody found a solution to the problem. I was wondering if it was mild wheel hop and with the close tolerances of the driveline, transmits it up to the engine. I had a post about tight driveshafts and difficult removal and a couple people chimed in about the same thing. Could shortening the driveshaft by a quarter or half inch help this?
Wheel Spin Knock
- Thread starter GN HEAD
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You're robably hitting the rev limiter. Rpm. is limited on these motors by taking away fuel. This creates a lean condition,causing knock.
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tight driveshaft, in that you cant slide it toward the trans to get the rear joint free of the rear axle yoke is usually from a twisted front yoke where the splines have actually shifted , not uncommon with the stock yoke on cars that have been launched hard
like this...
like this...
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the problem is not is the driveshfts guys or at least not when my car was doing the same thing.
My problem was from the speedo cable getting whiped back and fourth from say 80 mph and when it hooked up it would whip back to 10-15 mph.
the speed sensor is located on the back of the speedo cluster so it see this whipping action too.
well as this happens the stock ecm gets lost in the program so to speak because the load table are configured by the use of the speed sensor input so a rapid change in speed wheather i's from stopping suddenly of having you foor to the floor and the tires spin and then grip the speedo cable whips back for a split second.
well in that split second even tho your foot is still of the floor the ecm thinks that since the speed/load changed and your not in PE mode and switchs into AE mode. when it switchs into AE mode for that split second it changes the timing tables also along with the fueling so now the engine is at full boost and the timing and fueling changes for a split second well that split second just causes your wheel spin knock.
my car only done this on the street and not at the track. it took using direct scan to find out the problem.
i went and got a heavy duty speedo cable and it helped it some.
good luck
i also have the direct scan files from it too if ya wanna look at it.
My problem was from the speedo cable getting whiped back and fourth from say 80 mph and when it hooked up it would whip back to 10-15 mph.
the speed sensor is located on the back of the speedo cluster so it see this whipping action too.
well as this happens the stock ecm gets lost in the program so to speak because the load table are configured by the use of the speed sensor input so a rapid change in speed wheather i's from stopping suddenly of having you foor to the floor and the tires spin and then grip the speedo cable whips back for a split second.
well in that split second even tho your foot is still of the floor the ecm thinks that since the speed/load changed and your not in PE mode and switchs into AE mode. when it switchs into AE mode for that split second it changes the timing tables also along with the fueling so now the engine is at full boost and the timing and fueling changes for a split second well that split second just causes your wheel spin knock.
my car only done this on the street and not at the track. it took using direct scan to find out the problem.
i went and got a heavy duty speedo cable and it helped it some.
good luck
i also have the direct scan files from it too if ya wanna look at it.
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never said it was the cause of his knock if you look at the original post there was a second question regarding the driveshaft
"I had a post about tight driveshafts and difficult removal and a couple people chimed in about the same thing. Could shortening the driveshaft by a quarter or half inch help this?"
and i feel i gave a valid response to that question
most modern chips have false knock ignore during luanch due to the fact that spinning will cause driveline vidrations as will hard shifts and can trigger the knock sensor
if you ever run a chip that doesnt have this youll find it nearly impossible to get a good run with the retard affecting timing and the slow recovery, i had to use an old street chip (not a TT chip) when i switched to 55# injectors and it did not have false ignore and would pull all timing and maintaned some retard all the way through the gear and on shift would start all over over again , my kr on DS looked like a reverse of my rpms
Also on the driveshaft issue. The performance cars with the 8.5 had a slightly shorter driveshaft to make up for the extra size of the 8.5 rear axle, and it is possible that someone slipped a 7.5 shaft in it. Pay attention to where the yoke slides in and see if it looks like its going all the way in or not. I've never personally seen the two driveshafts side by side so I don't know the exact length difference, but i've read that it's 1 or 2 inches shorter. Just something else to check.
I have no input on the knock but my car does the same thing. Always has.
bob
I have no input on the knock but my car does the same thing. Always has.
bob
the false knock ignore is what i had on my extender extreme and it still had those same problems.
I didn't mean to step on anyone's toes here. sorry that you took that the wrong way.
i'll be sure not to post any information in any of your posts since i may make you look to be wrong or something.
GN head hope you get it solved later
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sorry you feel that way , i wasnt flaming or anythingthing just discussing . no exclamation points or caps , maybe you felt i was off the topic but it was part of the post
hope you dont hold it against me as i felt your input on KR and wheelspin was well explained and may just be the culprit
no harm done. also i didn't think it was off the subject. I should have not stated what i did. my appoligies (sp).
I took it the wrong way.
Thanks for all the input....some that I hadn't heard of or thought of. It seems to be a problem with several cars...some don't have the problem with the wheel spin knock. The exhause crossover and downpipe all are clear of the frame..so I don't think that they are involved in the problem....have always wondered if it was RPM changes that were quicker than the ECM could react to....to, it would be actually a lean condition.....real knock. Who knows......I might just have to live with it....dealt with it long enough.... Again, thats for all the input...it gave me a lot to check on and if I ever get to the bottom of it, I'll post the remedy.
I've had an issue with kr and wheel spin as well turned out to be a boost spike problem in my case. Cost me a set of hg's before I had it figured out. It would only spike when the tires came unglued.
Might check your boost gauge when the tires break loose.
Might check your boost gauge when the tires break loose.
Russ Merritt
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You could try and stop the wheel spin.
My Terry Houston downpipe hits the top of my frame,and I never see knock from it. If anyone were to see knock as a result of there downpipe hitting something,it would happen while the car was making good power and getting good traction. This is when the motor is forced to twist. During wheelspin the pressures are taken off the motor. False knock can't be caused by the downpipe hitting the frame,when the tires are spinning,because the downpipe moves away from the frame when this happens.The first thing I would susspect is that the knock sensor is too tight. The factory spec is 14 ft./lbs. Loosen your sensor and take note as to how much effort it takes to do so. It shouldn't take too much effort,as 14 ft./lbs. isn't very tight. If you don't have a torque wrench,tighten it noticably less according to feel. It'll make a difference. If your injecting more alcohol than needed too stop knock that doesn't exist this adjustment might even lead to you replacing head gaskets for the last time
84BuickGNYorkPA
Daily Driving Buick V-6 Turbo's 1979 - Present
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I got the same thing, working on preventing wheel spin angle, (Nitto street radial 50's, new aftermarket upper and lower control arms,fresh Moog springs).
Chuck
Chuck
Turbo1dr
9 Sec Wanna-Be
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But...but...but that's not cool when you can't spin the tires...lol. :biggrin:
"try to stop the wheel spin", I guess I'm not following you.........I'm not trying to spin, on hard launches with sticky street tires it will still break loose and spin. Anyway, I've checked the torque on the knock sensor....it's good.....the culprit is still at large on this one.
Russ Merritt
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An 11.90 car should be pretty easy to hook up.....GN Head, how are you launching, foot brake, T-brake? How much boost are you trying to launch with? Are your tires spinning before you let the car go? What are your 60's? Have you tried launching easy to make sure the tires hook and there is no knock? What tires? What pressure? Are the rear shocks good? You say you have wheel hop?
If you do have wheel hop, I'd be under the back of the car for now. Not under the hood.
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