please help, funny noise

[vw62rag]

hello, i have jus got my 85 k5 running, i put in a 355 and the motor runs great! but when i get up to 35mph or faster and totally let go of the gas pedal and jus coast i hear a kinda grinding/rattling sound from the tranny/tranfer case/rear axle area? it has a 700r4 and a 208. any ideas?
thanks

 

[mud390]

Maybe the chain in your 208 is strecthed and thats what you are hearing?

Kris

 

[vw62rag]

is that bad? lol im a total newbie at 4x4 stuff

 

[mud390]

A NP208 is a chain driven transfer case. I can't remember the site that has the breakdown, but I'm sure someone while chime in with it so you can see exactly what I'm talking about. Over time the chain will stretch some which in the end, when its stretches far enough, it could break. Have you checked the fluid levels in the tranny and xfer case?

Kris

 

[vw62rag]

i jus cleaned out the oil in the front and rear axles and the transfer case(drained them and filled them with gear oil) and i emptyed the tranny and filled it back up with tranny fluid(and changed the filter).

 

[GMCLegacy]

that tcase should take ATF, if you put gear lube in it, that could be a problem.

 

[vw62rag]

aww man does it take auto trans oil? i put gear oil in it.

 

[85mudblazin]

yea that is prolly causeing it gear oilt is a lot thicker than atf so that might be causing it. /forums/images/graemlins/thumb.gif

 

[vw62rag]

so i take it i should put in auto trans oil? guess ill do it and let you all know what happens.
thanks for the help everyone!

 

[vw62rag]

im gona try to change the oil tommorow, but do you think i damaged anything by using gear oil? i drove it no more than 50 miles with it on the street in 2wd

 

[k-5 jimmy fan]

208 has a oil pump, it may not be liking the thicker lube, drain, fill with ATF, see what happens.

 

[CyberSniper]

[ QUOTE ]
208 has a oil pump, it may not be liking the thicker lube, drain, fill with ATF, see what happens.

[/ QUOTE ]

They do, eh?


I'd just drain the gear oil out and put ATF in. GM's "fix" for noisey NP207s, NP208s, NP231s, and NP241s was to add 1 pint of gear oil.

 

[vw62rag]

thanks for the help everyone! i hope its nothing to serious. ill do the oil swap no later than this friday, and ill let ya know what happens.

 

[vw62rag]

well i finally drained the gear oil out and put in some auto trans oil and i belive it worked, i drove it all day today and it seems fine now! i didnt hear the noise. thanks guys!!