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Discussion Starter · #1 ·
Hi, I'm kind've new here and my '99 Rodeo has developed a problem that I think I know the cause, but don't know what to do about it. The vibration starts around 40MPH and stops after 50MPH. It peaks at about 45MPH. I'm sure this has happened to others, but I couldn't find an answer by searching (wrong subject probably). Anyway, I think it's the lockup torque converter not locking up all the way, and it shudders sort of. I guess if I could find the wire that makes it lockup, I could just cut it, but what about the OBDII? Wouldn't that set a code or something? Is it fixable without replacing the trans? I guess an alternative would be to swap out the auto trans for a 5 speed. By the way, I forgot-mine is a 2WD Rodeo. Thanks for any help or ideas.

Jim.
 

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It is easy to test your theory. When the brakes are pressed the torque converter has to unlock. So get yourself moving at a steady 45mph. With your left foot just touch the brake pedal. This will tell the computer to unlock the torque converter. If the vibe is still there, it isn't the torque converter clutch.

-Tad
 

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Discussion Starter · #3 ·
Thanks, Tad. I have to work today 'til 2pm. I'll check that out on my way home after work. I have about 6mi to test it. If it turns out that's what it is, can you bypass the lockup circuit to make it stop? It sounds like there's a circuit that tells the PCM to unlock the TC whenever you hit the brakes. I guess if it didn't do that, the engine would stall upon stopping. Thanks-Jim.
 

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I don't think you want to permanently unlock the torque converter. You want the converter to lockup as that is much more efficient. In fact I suspect the fluid would tend to overheat if it didn't lockup while driving at highway speeds. Then again ATs are mostly a mystery to me.

There are also numerous other possibile causes for your vibration - bad u-joint, tranny or engine mount problem, bent rim or unbalanced tire come to mind.
 

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Discussion Starter · #5 ·
I tried the tip of pressing the brake pedal under light cruise. I haven't been able to tell for sure one way or another yet. I have checked tires, rims, balance, driveshaft and u-joints, engine and trans mounts-all is tight, true and secure. I'll keep trying though, thanks.

Jim.
 

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Is the tranny fluid in good shape? If it's been a while, a flush would be a good idea. Running a "T-Tec" flush is typically around $150 or so (at least, in my area), and it does a better job than just draining and refilling what's in the pan. I've seen people here saying that dropping the pan and the accumulator cover gets about 75% of the old fluid out and allows you to change the trans filter, but YMMV.
 
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