[savenger]

Hi All,

I'm kinda new, so forgive my ignorance if there is already a thread on this.

My '85 Sierra is making a grinding kind of noise when I accelerate in 5th gear. Sounds like it might be a worn bearing or lack of transmission fluid or something, but I'm no mechanic so honestly I have no idea...

What are some likely causes? Is this something I should get checked ASAP?

[Abraxix]

tail shaft out of balance? wheel bearings? at high speeds? gearbox about to let go?? then again these are just things i'd suspect if it were mine and having said that i drive a vitara... but still i'd be even maybe guessing could be your diff???

any ideas as to narrow down where the noise is coming from?? could be tire noise? road noise? again at higher speeds??

Abs!!!

[savenger]

It's not related to speed at all, or revs... Just 5th gear.... It's like as soon as I change from 4th to 5th it starts grinding. It sounds like it's probably coming from the transmission.

[savenger]

Oh, and if I'm just idling in 5th, going down a hill or something it's fine... just whines a little as you'd expect... It's only when I accelerate that the noise starts.

[SuziBlu]

5th is overdrive, and quite a weak link in the box, it could be that it is rooted, bearings shot.

5th will only drop ya revs by a little, 2-300, so till you can get it out of the car and rebuilt, don't use it, just use top.

[Abraxix]

diff!! at least that's my guess, hmmmmh transmission as well then if it does it at the same time as your idiling your car
otherwise it would have to be transmission???

generally somehitn that you'd want to get checked up on semi sooner rather than later, unless you have the same attitude as some,

give it to it untill it snaps / breaks and it'll never break then, otherwise treat it reall gentle and safe slow and nice and it'll break on you sooner >.<

[303zuke]

The 5th gear on the mainshaft has it's gear teeth angled so that when drive is applied off the countershaft gear, the gear is thrust backwards. There is a thrust washer that supports it (and that may be worn or missing), and that sits against the rearmost Roller Bearing which is held on to the mainshaft by a circlip (which also may have come loose or be missing).

If there is any rearward play on this mainshaft 5th gear, it will move backwards and make grinding noises by either fouling the rear case housing or wanting to disengage from the synchro ring.

[savenger]

Thanks guys, that helps a lot.

I guess now I'll cross my toes and hope my mechanic knows what he's doing.

Can anyone recommend a good mechanic in sydney?

[lump_a_charcoal]

I go to Hitech, out an Penrith.

Dude, I bought a 5 speed for $80, I would try htat before getting a gearbox rebuilt.