Transmission slip problem or something else?

[jgr]

I'm trying to determine if I have a transmission issue and if so what to fix.

When I stop at a long light (in gear, brakes applied) I usually get a sharp bump, or series of bumps. The interval between bumps is random. Also does it if I put it in park without brakes applied. If I let the truck creep along with just a little bit of throttle I get a series of bumps that feel like a grab/release/grab/release.

1998 V6 4WD Auto with 181k miles. No codes found using OBDII scanner.
All maintenance is up to date: new wires, plugs, filters, coil resistance within spec, etc.
Compression is 190-195 psi on all cyl.
I did a drain and fill on the trans fluid (didn't drop the pan). Fluid was old but not burnt.

Any suggestions? Thanks,

Jon

 

[Nelsonmd]

I'm trying to determine if I have a transmission issue and if so what to fix.

When I stop at a long light (in gear, brakes applied) I usually get a sharp bump, or series of bumps. The interval between bumps is random. Also does it if I put it in park without brakes applied. If I let the truck creep along with just a little bit of throttle I get a series of bumps that feel like a grab/release/grab/release.

1998 V6 4WD Auto with 181k miles. No codes found using OBDII scanner.
All maintenance is up to date: new wires, plugs, filters, coil resistance within spec, etc.
Compression is 190-195 psi on all cyl.
I did a drain and fill on the trans fluid (didn't drop the pan). Fluid was old but not burnt.

Any suggestions? Thanks,

Jon

Sounds to me like you are low on ATF. Check the dipstick. If it is ok, try adding a little bit of ATF (like 1/4-1/2 qt at a time) and see if that fixes it. It is better to check the ATF temp when it is at operating temperature rather than cold. IIRC mine is sitting pretty high in the hot range; I had trouble getting to work smoothly without going way over the hot range.

 

[jgr]

ATF level is on the on the high side of the hot range after driving 25 miles. Adding any more fluid and I'll be overfilled.

Could this be a torque converter going bad? I does it in park too. Should I *gasp* take it to a shop? I'm reluctant to take it anywhere b/c my experience with most repair shops is 'no CEL, no problem'.

 

[kball]

In park without brakes and you feel bumps? I think you have an engine missfire. Plugs were just changed? What kind were put in?

 

[jsmarine]

In park without brakes and you feel bumps? I think you have an engine missfire. Plugs were just changed? What kind were put in?

My thoughts too. I had a spark plug come loose and cause a missfire. It wasn't completely out of the threads, but loose. It was my fault as I did the plug change and obviously didnt tighten that one down enough.

Check your plugs, as I had the same symptoms as you.

 

[Ian97]

Bumps or maybe a jolt? I had this when I had the tranny fluid flushed, turns out I was a bit low on fluid, I added about a 1/2 quart and it fixed the problem. I also experienced when I'd leave from a stop light, there would be a slight hesitation. I was able to test this a few times by stopping suddenly as well as gracefully....this seemed to happen when I'd stop suddenly at a stop light or stop sign. Adding the fluid cleared all this.

Now, not sure this helps your exact situation as you said your fluid is on the high side.....but I have experienced your symptoms myself....

Hope it helps somewhat....

-Ian

 

[jgr]

Thanks for the replies. I scanned it one last time and BINGO a pending code for misfire on cyl #1. I already have new plugs & wires so I bought a bosch ignition coil and ... It's WORSE!? I have to run the original OEM coil pack else I get an immediate misfire code cyl #1.

It appears to be a bad coil but is there anything else up stream that can cause this? I'm at a loss.

Thanks,

Jon

 

[kball]

A misfire on just cyl 1 is most likely the coil/boot, plug or injector. As you've already seen Bosch doesn't work well with these trucks. You still never said, what kind of new plugs and wires do you have?

 

[jgr]

NGK wires.
Bosch Platinum +2 plugs. So should I try NGK plugs?

I thought Bosch made good stuff but the more I read the less it appears to be true.

 

[kball]

Bosch may make good stuff but these trucks rarely like it.

 

[jgr]

Just wanted to follow up...I put in Deno copper plugs and the problems have gone away. I'm amazed at the difference. Thanks for the help.