97 OBS INTERRMITTENT LOUD HARSH METALLIC BANG WHEN ACCELERATING FROM STOP.

[JMWRIGHT335]

Hello, First things first its a pleasure to be apart of your community of oil burners and I thank you for any help you may provide now and in the future.

With that said, as my title states i have a 97 powerstroke OBS with only 103,000 on the odometer, truck is mint and everthing that has ever needed to be done has been done immediately no questions asked, I am a technician with BMW so im very automotively inclined though auto trans are not my bread and butter. My situation is every once in a blue moon maybe once every two weeks i will have a very harsh engement along with a very loud metallic banging noise. Now this can happen at operating temperature or cold. I will come to a stop say for a red light and light turns green i come off the brake pedal and lean on teh gas, not hard, just driving miss daisy style and it will give me the loud bang noise. There is no delay assosciated with it and no slipping of the transmission either. Prediminantly I would check u-joints and pinion shafts however this is so intermittent that if something was loose I would antiscipate seeing it more frequently. Any help would be appreciated, thank you for your time and assistance.

Truck is a 1997 OBS powerstroke automatic E4OD 4 wheel drive. Truck is 95% stock. I have recently installed a 5 inch complete exhaust with a 3 inch downpipe, but to clerify this has been happening since before the exhaust was installed, and the prior exhaust was factory. Truck has no lift, no chips, trans fluid has been changed frequently and is currently clean as a whistle. No obvious u-joint play all front end components are tight with no play in steering wheel or otherwise.

 

[94f450sd]

Check your rear brakes.make sure the shoes arent sticking out when you get off the brakes,a leaky wheel cylinder or axle seal will cause that.

Being a mechanic,(hopefully like me.)you should have somewhat of an idea what end and side the noise comes from?

Its also slightly possible you have a chipped or missing tooth on the ring and pinion.

Does it have a limited slip differential?try adding a bottle of limited slip additive.sticky posi clutches will make a noise like you describe.

 

[JMWRIGHT335]

I will remove and inspect after work today however I do know at this point I do not have and wheen cylinder or axle leaks.

The noise is so random it usually happenes when ive completely forgotten it even does that occationally making it difficult to ascertain but from what i can tell it seems to be coming from exact middle. Broken tooth sounds the most plausible however I would think if that were the case I would be able to feel it conscictantly during slow acceleration such as making u-turns or especially heavy towing.

It does have LSD, I will change out the fluid this week as well, But ive never come across an LSD diff that will make a noise like this.

The noise sounds like if you were to take a steel chain and whip it across a steel wheel barrow as hard as you can... Thats the best way I can describe it.

 

[94f450sd]

Id try the dif additive.sticky dif clutches will make all kinds of different noises all the time or once in a while depending on how sticky they are.

You can just add the additive,no need to drain unless you want new gear oil in it.

 

[JMWRIGHT335]

Yea, At that point id rather just remove it and install new that way I can inspect the fluid quality thats in there now for any deposits. What fluid and additive would you recommend?

 

[OLDBULL8]

Use only synthetic 80-140, takes about 4 quarts for each one. On my 99 PSD, water got in my generic module and would try to make it shift into 4WD, hell'va loud bang under your butt, $450 for the module and $100 to program it, I said hell no, just cut the wire at the motor and installed a ON/OFF switch to power the shift motor. Windshield leak on drivers side, module is on drivers side behind kick board.

Hey, welcome to the OB.

 

[sle2115]

Might be loose torque converter to flywheel bolts too. Maybe not super loose, just enough to allow it to slide around under certain circumstances. I would check out the other issues but might not be too hard to slip inspection plate off and see if you can slip anything around with a pry bar, mainly rotational. Check bolt torque while in there. Just a thought. I'd go nuts trying to replicate it!

Oh, and welcome to OB

 

[fordf350man]

just in case when you check the u joints put the truck in nuetral, i had bad u joints and just sitting in park there was tension on it and couldnt tell there was u joint play, once i put it in nuetral i found 3 bad u joints, also not sure if you have the long drive shaft or not but i had a center support bearing that did alsmost the same thing that your describing, might want to check that also, hope you get it fixed

 

[OLDBULL8]

Might be loose torque converter to flywheel bolts too. Maybe not super loose, just enough to allow it to slide around under certain circumstances. I would check out the other issues but might not be too hard to slip inspection plate off and see if you can slip anything around with a pry bar, mainly rotational. Check bolt torque while in there. Just a thought. I'd go nuts trying to replicate it!

Oh, and welcome to OB

I know exactly how to replicate it, just loosen about 4 of the six nuts. Cost me $3000 for a tranny rebuild and TC in Grand Island Nebraska. But the sound is more like shaking marbles in a empty can, until a bolt on the TC actually tears open the TC case when shifted from Fwd. to Rev.

 

[JMWRIGHT335]

OK so far ive found the center bearing to have some excessive play but not too bad, that's on order now. None of the u-joints have any play and are all spicer sealed joints. I did discover its got a lock-rite locker in the back. ( found pamphlet hidden in my owners manual ) so i could see that being an issue ill find out for sure when I crack the pumpkin though.

 

[JMWRIGHT335]

Luckily my truck has no leaks, Water leaks drive me crazy and I had the headliner out for about a week having it reupholstered and also installing my cab lights and i had some wicked heavy rains that week with not a drop inside and no evidence of any attempts to a water leak. I do fear the trans is inevitable on its way though, get a lot of erratic shifts going down the road like it cant decide if it wants to be in 4th or OD or TC locked or unlocked so that gets irritating but otherwise no real complaints so.

 

[Can30Diesel]

I had some nasty banging sounds in the rear diff on my truck for a while. I thought it was badly adjusted breaks but in the end it turns out the previous owner of my rear diff installed a detroit locker and never used any additive.

I drained the fluid, put some amsoil synthetic and amsoil addative in it and the rear diff shut right up. Until that point, I thought something was going to blow up back there. As a side note, I actually have good traction on soft gravel and such again in 2wd.

 

[JMWRIGHT335]

What viscosity oil did you use?

 

[trackspeeder]

Luckily my truck has no leaks, Water leaks drive me crazy and I had the headliner out for about a week having it reupholstered and also installing my cab lights and i had some wicked heavy rains that week with not a drop inside and no evidence of any attempts to a water leak. I do fear the trans is inevitable on its way though, get a lot of erratic shifts going down the road like it cant decide if it wants to be in 4th or OD or TC locked or unlocked so that gets irritating but otherwise no real complaints so.

The erratic shifts could be the transmission range sensor on its way out.

 

[JMWRIGHT335]

Are you referring to the PRNDL switch or is it a different sensor? If so where is it located and How xould I test it?