Author Topic: Odd noise in 2WD and sounds fine in 4WD  (Read 1495 times)

Offline dustygriley

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Odd noise in 2WD and sounds fine in 4WD
« on: January 22, 2018, 08:29:29 PM »
Ok I came across one thread that was close to my issue but mine is the opposite of the thread I read. 

Had the old boy out hauling firewood this weekend and with a full load (78 long bed K20) going up a rather steep incline on large rock I could feel the front end pulling as it should.  At the top things started to "click" a bit but luckily I was at the top and done needing the 4x4.  On the way home about 30 miles in 2WD I could hear a slight rattling noise coming from the crank shaft area.  Nothing banging or anything like that but when throttling up hills or even just coasting I could hear a slight rattle in there and very inconsistent and sporadic.  The next day with the load of wood off I took it for a spin down the road and the same noise was heard again.  So I shifted into 4hi and everything locked in and no noise at all other than the whining of the extra grip.  Took it out of 4wd and it started all over again.  I know I said the truck is a 78 but it's got a TH400 and a 208 transfer case.  Any thoughts or ideas as to what it could be?  Likely going to yank the transfer case out this week and have it rebuilt.  Would much rather put in a 205 but my expertise is limited and not sure what all I would need to change out to swap the 208 with a 205????  Any thoughts or suggestions????

Offline VileZambonie

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Re: Odd noise in 2WD and sounds fine in 4WD
« Reply #1 on: January 22, 2018, 08:57:33 PM »
Inspect. It can be anything, but throwing a transfer case at it won't prove much. Check your U-joints and hubs
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Offline Irish_Alley

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Re: Odd noise in 2WD and sounds fine in 4WD
« Reply #2 on: February 01, 2018, 07:30:36 PM »
just another detail but does it have manual or auto hubs?
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline dustygriley

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Re: Odd noise in 2WD and sounds fine in 4WD
« Reply #3 on: February 02, 2018, 10:01:46 PM »
It has manual hubs.  I'm not positive but I'm thinking it's a U-joint.  I'm not positive of t1his but I will be inspecting it further this weekend.  Luckily this is a working project truck and not something that I have to have running at all times.  It's more of a weekend driver than anything.  I did drive it 112 miles round trip this last Monday evening.  The same noise came from where the transfer case is.  If it's not a U- joint then it is definitely something in the transfer case.  I'm pretty sure it's not the transmission itself, it shifts nice and easy and the noise seems to be coming from further back.  I did notice that it only makes the noise when I let off the foot feed.  So to me it's only when there is what I call back pressure on the transmission when it makes the noise.  You know, not when you give it gas but just when you let off completely.  As long as the transmission is pulling everything sounds fine but when it's so going down a hill and no pressure on the gas then it makes the noise.  Yes I will be inspecting in more detail soon....

Offline Irish_Alley

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Re: Odd noise in 2WD and sounds fine in 4WD
« Reply #4 on: February 03, 2018, 03:40:19 PM »
right now its pretty much a guessing game but like vile said i would think it would be the u joints. when you give it gas the trans is pressing on one side of the u joint to turn it when you let off the axle is pressing on the other side to turn the transmission
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes