87 Automatic, do I need to replace it??

[TOY2G]

I have an 87 with an automatic, when I am coasting down the road (not under acceleration) the thing make a SUPER loud growling noise. Stepping on the gas cuts the noise out about 90%. I thought it was the rear end, but I checked the fluid, and it looks good (I changed it about 3k ago).

Anyone think it is the bearings in the tranny (my guess). Just not sure if it were the bearings, if they should not make the noise even under power?????

I am will be sitting here staring at this computer until someone tell me to go do something else, so feel free you chime in if you have dealt with this issue.

layball:

 

[KidVermicious]

Could be the trans I suppose. Could be the transfer case. Could be the driveshaft ujoints. I'd start with the cheapest and check those ujoints. If they seem nice and tight, drop the driveshaft and drive around in 4wd, see if you can make it happen again. If yes, then you've ruled out the rear end and driveshaft, and can start hunting for another transmission.

The A340F is cheap when you can find them - I see them for under $100 here.

 

[fourwd1]

Even tho u checked the rear diff fluid, don't rule it out.
U may want to drain a little out and check for metal.

 

[TOY2G]

Could be the trans I suppose. Could be the transfer case. Could be the driveshaft ujoints. I'd start with the cheapest and check those ujoints. If they seem nice and tight, drop the driveshaft and drive around in 4wd, see if you can make it happen again. If yes, then you've ruled out the rear end and driveshaft, and can start hunting for another transmission.

The A340F is cheap when you can find them - I see them for under $100 here.

I have looked for a rebuilt one, with little to no luck. I should have mentioned, I replaced both rear u-joints roughly 2 months ago due to some serious squeaking.

Even tho u checked the rear diff fluid, don't rule it out.
U may want to drain a little out and check for metal.

I thought the same thing, however when I drained it to change the fluid, the old stuff was pretty dirty, but very very little shaving in it at all. when I pulled the plug yesterday and looked inside, i could see no damage to the ring gear. I guess it could be the pinion???

 

[fourwd1]

I was thinking maybe the pinion bearing.
Maybe put the entire truck up on jackstands, put it in gear and see if you get the noise.
If you do, then pull the rear drv shft off at the t-case and see if you still have the noise.
That'll help eliminate things.

 

[KidVermicious]

I have looked for a rebuilt one, with little to no luck.

Rebuilt? Piffle and hogwash I say. That auto may be a worthless power sucking dog, but it's a reliable worthless power sucking dog. They don't go bad very often - I'd get one on the cheap from a guy parting out and run with it.

Assuming the one you have is bad, of course.