Calling All Owners of ENF510 Engines w/ 5 Speed Transmissions

[fxfymn]

I have been chasing a strange noise that occurs in my truck when you decelerate while it is in fifth gear. It sounds like diamond plate rattling, but its not, and it gets louder at high speeds. It is quite loud and only occurs in fifth gear while decelerating; as soon as I step on the gas it disappears until I let off of it again.

When I was in SC this week I had the chance to ride in the sister truck to mine and it does the exact same thing. Now I'm wondering if its normal or something that is a common malfunction.

So, does anyone else experience a loud roaring,rattling vibration type sound in a rig equipped with the ENF510 and a five speed (fifth over) transmission that occurs when you are in fifth gear and let off of the accelerator? That would include some E models, Type 75A, and Type 505A among others. And if so, have you figured out what the cause is?

[609albert]

What area of the truck is it coming from, front ,rear etc? could be universal joints,loss plate under truck,loose connection for the tag/ speedometer cable, has it done this since you owned the truck?

[fxfymn]

Yes. it has done it since I bought it. So far I have rebuilt the transfer case and the differential. Since it only occurs in fifth gear I am pretty sure it is in the tranny and is most probably gear lash caused by end play from an incorrectly shimmed shaft.

But, it really threw me when the sister truck to it did the exact same thing. (Mine is 1028, the other truck is 1029 and they are virtually identical) The drive shaft is tight and since the noise does not occcur at the same speed when it is in fourth as it does when it is in fifth, I doubt it is in the driveshaft or universals.

Beleive me, any and all ideas are welcome. It is driving me crazy.