Ok, i'm no technician but this morning when i was on my way to work, i pulled up to a stoplight and when it turned green, i put the pedal at about half or 1/3 throttle, and the whole dash rattled and shook at about 1500-2000 rpm, then went away, and came back on when the car downshifted on the freeway from 4th to 3rd at about 45mph. I can duplicate this anytime i am in 4th gear and mildly accelerating from 35mph up past 40. It occurs in more than one gear, and happens under part throttle. Any ideas about what is up? Is it a fuel problem? it doesn't feel like a miss, and when the car is not in gear, and i slowly rev it up, there is no sign of a miss. I popped the hood in the parking lot and nothign seemed out of sorts. it almost feels like spark knock, but it goes away under full throttle, it is only at part throttle. Could it be a tranny problem? Maybe the lock up convertor? I am putting this on both the tbi and tranny boards, as i don't know which it could be related to.
Any help would be greatly appreciated.

thanks,
Mike

 

I get this aswell sometimes with my T-5.

 

I hate to say it but your two problems are unrelated so to speak. The auto tranny has a tc lock up problem, while the staight shift MAY be clutch related.

There are a couple of things you can do to see if the tc is the problem.

1. When you start to feel the vibration push the brake pedal down just far enough to disengage the tc clutch, not enough to slow the car down. You might want to try this on level ground at say 60mph so you can get a feel for how far to depress the brake pedal. You should also be able to see (if you have a tach) the rpm's go up a little, or hear the engine speed up a little. If the vibration stops when the converter is disengaged you have found the problem.

2. You could put the trans in second when you feel the vibration starting but this sometimes masks the problem.

This vibration only seems to happen when you are excellerating slowly or in my case it happens when I'm going up a hill as the tc trys to lock up at part throttle. I think if the problem just started you should have good trust worthy shop flush and refill the trans fluid along with a new filter. This alone could stop a lot if not all the vibration you have.

As for the straight shift, you might need a new clutch or maybe just a trans mount.

Steve

 

I'm no expert - so I pose this as a question.... Could it be bad U-joints in driveshaft? That problem always worries the hell outta me, because I once saw a car do the pole vault thing at about 35mph - it wasn't pretty, and that driver was hating life that day! Hence, I'm paranoid with any vibration that I can't pinpoint to a definite engine problem.

 

It's possible but a bad u-joint usually will get worse as speed increases or as more power is applied.

Steve

 

Wow, thanks for the help, i am already taking it in on friday to my transmission shop, who are excellent, i will definitley do a fluid flush with them and a filter. I will let you guys know what comes of that. I hope that it is nothing major...keeping my fingers crossed. Will try the things you all mentioned in the mean time. THanks again.

mike

 

Ya mine is only in 1st gear with slow acceleration, I was thinking tranny mount but I guess the fluid is a possibility, the clutch is fairly new so I doubt thats the problem. But im open 2 all possibilities so ill check it out thx guys.

 

DA, I don't think it would be your trans oil in a straight shift. I would ask over at the transmission and drivetrain board and see what kind of answers you get there.

Steve

 

I am having the exact same problem with my '94 truck. It has been doing this for a while now and i am losing my patience!
I have change plugs,wires,cap,rotor, IAC, Vacuum lines, Tires, And fiddled with timing and TPS voltage. Nothing helped.

The thing is my tranny and TC are new with less than 8000 miles on them. The U-joints aren't very old either. I can't express how grateful i would be if someone could figure this out!!!!

I am going to try a new TPS this week and see what happens.

 

Check the plugs, that is what i had a problem with too. Did you replace them after you had the shudder or did the shudder start after you replaced them? My plugs were new, and i had cracked the insulator on one of them (#8) it was grounding and this is what caused my shudder. Took me 99cents to fix it after taking it to 2 shops and spending 380.00 combined to have one tell me it was a 1700.00 tranny rebuild and another say it was a set of plug wires. Well, they were both wrong. Check the car with the hood up and running in the dark (be careful of those belts and blades though) Just look, if you have this problem you will see a faint flash as the spark goes out the side of the plug and its the collar.

Mike

 

Well, I just put 8 new ac delco plugs, a new set of ac delco wires, and a new cap and rotor. No change. But this makes me think that is in the motor and not the new tranny, whew!! I will have double check all my ignition components. Would a dead lifter cause this problem, I have one that ticks and haven't had time to change it. It may have collapsed. Thanks for the good info it gives me a direction to look anyway. Any more ideas, send em my way.

 

Trust me check the plugs before you do anything, mine were very sensitive and i had just put them in also, i had this happen twice, one time immediately after i put the plugs in and one time a few weeks later. So it is worth a check. I don't know about the lifter issue though, not sure if it would cause that problem, i think that woudl just reduce lift? Anyway goodluck.

Mike

 

I will definitely give it a shot, my IAC was sticking shut last week and i had to get a new one, maybe it was rich enough to foul a plug or two. I need to go into the spark plug business!!!