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Vibration under acceleration...

1quikgp

1quikgp

New member
I have a 2000 GTP with a T.K. built trans. Originally when purchased from a forum member it was off a fresh rebuild. 300m, 1" 3.29 gearset, 3200 stall, etc... Milzy Motorsports did the install, and I had them verify what was there. It did have what was advertised, but about 2000 miles later it went back because of sloppy or no shifts at all, no 4th gear. They said the valve body was shot due to a ball misplacement in the valve body and required a full rebuild and a new valve body. All the hard parts were confirmed in excellent condition and reused, Zpaks and shift kit were installed. All work done by Tim King. Shortly thereafter, I started getting a growling/grinding noise and 3-400 rpm fluctuation during cruise. Lived with it for awhile, it was throwing no codes. A few months ago I had the converter replaced with a stock GTP converter. That took care of most of the the growling noise and all of the rpm fluctuation. Unfortunately I am getting a vibration under acceleration. Also when I back out of the drive, put it in drive, it will hesitate before engaging like it's in neutral for a second. This problem is intermittent, and still no codes.
The converter that was replaced is one unknown. All I know is that it was blue and smaller than the stock GTP converter. I have replaced all front end suspension parts and motor mount...Thanks DSmuts! I am lowered, but I kinda ruled that out since I didn't have a vibration before this trans. My trans tune is whatever was changed in the DHP 1.5 tune with the exception of the speedo tab. The speedo tab reads 3.29 as I was told the reluctor wheel had been replaced. In any case the speedo is spot on. I was told some people use a GT stock trans tune when using 3.29's, but looking for an opinion on whether this would be a good place to start or if it sounds internal and not tune related.
 


1quikgp said:
A few months ago I had the converter replaced with a stock GTP converter. That took care of most of the the growling noise and all of the rpm fluctuation. Unfortunately I am getting a vibration under acceleration.


The converter that was replaced is one unknown. All I know is that it was blue and smaller than the stock GTP converter.
Click to expand...

This doesn't make any sense.

What flex plate did you use?
 
Suspension feels great! Prolly even better after an alignment.

The converter and flexplate were on the trans when I bought it used. Not sure if it's stock GTP or other. I was just told after the rebuild that the converter was good, but it wasn't. I had a local trans shop put in the new GTP stock converter. He didn't mention that anything was out of the ordinary except that the converter was smaller, blue, and shot. Nothing about the flexplate.
 
Oh, I see. So you're sure it's a stock GTP converter in the car now.

The Tim King build may have been centered around a 3200 stall. This could be the problem.

Have you contacted Tim King recently?
 


Yes, stock now. I've tried getting a hold of him, but no response. Got a very quick response from another of our leading trans vendors...just saying. As far as I have seen in comparing stock GTP tune and my current tune nothing has been changed. Tim did not Tune anything that I am aware of. I had to tune the speedo myself when I got the car back from Milzy.
 
Being that the TC went after the valve body repair would concern me. The channel plate gasket may have been damaged.

Where's Bill when you need him?
 
As far as I know the TC could have been sketchy when I bought the trans. Like I said, I lost 4th real soon after they originally installed it so I have no clue what else could have been faulty. I know he said they completely replaced the valve body.
 
Yes, Dave is the one who told me some people use the tune from a stock GT, but not in so many words. Liability issues I'm sure. He didn't know if it would work or not. I do know I emailed him and got a response in less than an hour. Emailed my builder several times weeks ago and have heard nothing. Not flaming, just stating facts. Is it ok to just re post in that section, or is it more TEP specific?
 


You can post wherever you want. The moderators will let you know if there's a problem.

May be they can just move this thread over?
 
So I was getting some assistance at the HP Tuner forum and I am still pretty much at square 1. Here is the link GTP with 3.29 gear tuning help... - HP Tuners Bulletin Board I think I need to get the tune nailed down before I can diagnose any further. Anyone else tune 3.29 without using the stock reluctor wheel? Also is it difficult to check the actual gear set to confirm 3.29, and how difficult would it be to swap out the reluctor wheel if that's really what needs to be done?
 
Hi Scott,

I just replied to your email but wanted to share with others on the gear ratio change what I do as well as what a lot of others use in regards to tuning with HPTuners (this does not apply for DHP users!). I have made several posts with this info before but thought I would bring it back up as it has been a long while.

The stock GTP overall gear ratio is 2.93:1. You actually have a 3.29:1 final drive-differential ratio, but because of the drive/driven sprocket combination which is 37 drive and 33 driven this overdrives the transmission by 1.121:1 resulting in the adverstised 2.93: overall ratio.

The factory tune shows a 3.29 gear ratio and 1.121 sprocket ratio for the supercharged cars (with exception of 04+ compG 3.29 cars). A lot of people get in a mess over this and does not work how you think it would. You cannot simply plug in stock GT 3.29 gear ratio numbers on the entire speed page as it does not work- there are other numbers involved beyond what is on the available tables to play with in HPT so we have to use what is there- and its really simply.

When you are changing the sprockets to 35/35 this gives you a 1.00:1 ratio. You simply multiply the difference by the gear ratio in the tune, so 1.121 X 3.29 which comes out to 3.69. No- this is not your actual gear ratio, its just math that the pcm is looking at and needs to see a number to make things align correctly. A great feature with HPTuners is that it has the option to automatically skew all MPH related tables in the transmission portion of the tune- so falsely entering 3.69 will not only keep the numbers correct looking at input to output speed values, but also will skew all mph tables by the 12% change so you dont have to. It is one simple change that does everything at the same time.

You need to verify your gear ratio is being correctly seen by the pcm and to do this open up your scanner and watch "current gear ratio" and drive the car in 3rd gear. You should see 1.00:1 +/- .02 and then you know it is correct. NEVER turn off code P0730 for incorrect gear ratio!!!! Turning this code off when there really is a ratio problem opens a whole new can of worms and you cannot diagnose the problems if the code is setting but wont report- just turning the code off does not make the pcm ignore it and can cause a lot of side effects for no apparent reason. Leave the code turned on, it wont set if the tune is correct.


Now- whether this has anything to do with your problem at hand I dont know but as you mentioned you should make sure this is correct before going any further. Vibrations under load are typically driveline related or driveline angle related from a lowered car. I have heard similar stories before and ended up being a combination of wheel bearing and worn axle problems cause the vibrations. You just have to make a checklist of what was done when the trans was installed and start ruling things out since the vibration did not exist before. Was anything else replaced during the install? It can be as simple as a different mount or cradle alignment.
 
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