Th400 rattle noise

[wasted wages]

So I have finally been able to drive my truck for roughly 200 miles since rebuilding it. Both the transmission and engine only have 200 miles on them so they are new. Here's my problem I have a noise almost like a valve spring or detonation noise at roughly 2600 rpm. I have ruled out detonation and the torque converter bolts as well as flex plate bolts. It definitely sounds like it's in the bell housing area but as we all know noise can be deceiving. At this point I've heard it could be the parking pawl just touching but I don't think that would be an issue at only 2600ish rpm. I'm afraid it's the torque converter but I'd like to hear if any of you have had this issue before? Its also not the starter as the flex plate doesn't have a scratch on it either side.

 

[NickTransmissions]

So I have finally been able to drive my truck for roughly 200 miles since rebuilding it. Both the transmission and engine only have 200 miles on them so they are new. Here's my problem I have a noise almost like a valve spring or detonation noise at roughly 2600 rpm. I have ruled out detonation and the torque converter bolts as well as flex plate bolts. It definitely sounds like it's in the bell housing area but as we all know noise can be deceiving. At this point I've heard it could be the parking pawl just touching but I don't think that would be an issue at only 2600ish rpm. I'm afraid it's the torque converter but I'd like to hear if any of you have had this issue before? Its also not the starter as the flex plate doesn't have a scratch on it either side.

Have you checked trans fluid level when hot on a flat grade?

Does the sound occur when in all gears or just second and third (or just third)? Any noises when in reverse or park/neutral?

Any issues with transmission's function or performance?

Have you checked elsewhwre underneath for loose bolts, mounts, brackets, exhaust shielding, etc?

Parking pawl making contact would make noise anytime the vehicle is moving forward or in reverse so agree, wouldnt be the pawl.

Maybe do a line pressure test on the trans to see if the pressure is volatile, jumping around etc at idle rpm and stall rpm, if you havent already.

 

[wasted wages]

Transmission shifts correctly fluid is at the correct level and so far I can't find anything externally loose. The only time I hear the sound is in forward gears around 2600 rpm

 

[wasted wages]

I'm leaning towards either converter bearing noise or front pump.

 

[NickTransmissions]

I'm leaning towards either converter bearing noise or front pump.

If it was pump or converter, id think you would hear it all the time and it would vary by rpm...

Disconnect/unbolt the converter from the flex plate, spin the converter by hand while you put a mechanic's stethescope on the pump to see if you hear anything similar to what you're hearing when driving it.

Was the converter replaced when the trans was rebuilt?

Also please quote my post when you reply if you'd like me to respond as i dont get alerts ...

 

[wasted wages]

If it was pump or converter, id think you would hear it all the time and it would vary by rpm...

Disconnect/unbolt the converter from the flex plate, spin the converter by hand while you put a mechanic's stethescope on the pump to see if you hear anything similar to what you're hearing when driving it.

Was the converter replaced when the trans was rebuilt?

Also please quote my post when you reply if you'd like me to respond as i dont get alerts ...

I did put a new converter in when I had the transmission rebuilt. I'll have to do some more diagnostics this upcoming week. I've also ruled out the drive line components from best I can tell.

 

[NickTransmissions]

I did put a new converter in when I had the transmission rebuilt. I'll have to do some more diagnostics this upcoming week. I've also ruled out the drive line components from best I can tell.

Worst case, if you cant find anything external and sure its the trans or converter, just yank it out and bring it back to the trans builder for inspection and warranty repair, if that becomes necessary.

 

[wasted wages]

If it was pump or converter, id think you would hear it all the time and it would vary by rpm...

Disconnect/unbolt the converter from the flex plate, spin the converter by hand while you put a mechanic's stethescope on the pump to see if you hear anything similar to what you're hearing when driving it.

Was the converter replaced when the trans was rebuilt?

Also please quote my post when you reply if you'd like me to respond as i dont get alerts ...

I drove the truck again today and when I listen closely I can here the same noise very faintly when I'm moving in gear. I'm leaning heavily on the converter being the issue. My reasoning is because the transmission shifts correctly holds gears as needed and so far the fluid is still clean. I can't find my pressure tester or I'd test line pressure.

 

[NickTransmissions]

I drove the truck again today and when I listen closely I can here the same noise very faintly when I'm moving in gear. I'm leaning heavily on the converter being the issue. My reasoning is because the transmission shifts correctly holds gears as needed and so far the fluid is still clean. I can't find my pressure tester or I'd test line pressure.

Then yank it out, take the TC back and have it replaced under warranty; if no warranty, grab a new one from a reputable supplier. Alternatively, you can take it to a local builder to be overhauled. Perhaps a torrington bearing is coming apart inside the converter...

You're there so in a better position than any of us to diagnose noises, etc...

 

[Schurkey]

I have finally been able to drive my truck for roughly 200 miles since rebuilding it. Both the transmission and engine only have 200 miles on them so they are new.

WHO rebuilt the transmission? You should drive the truck with whoever rebuilt the trans, so that they can figure out the problem. That's why you paid them.

Unless, of course, you did it yourself.