well lets just say that i'm loving it. alot of fun to drive but 5th and 6th gears have a humming sounds when cruising, what could it be?

It sounds like gears but i hope its the the synchroes.

1 through 4 are fine with the normal noise that alot of people on here have, but 5 and 6 is a lot louder, it shifts perfectly fine.

 

It's probably just gear noise or maybe a bearing going out. I doubte it's the syncro. I can't remember but I don't think they rotate on the shaft so they shouldn't be making any noise. Might be the shift fork if the pads are shot. Does it get louder or quieter if you move the shifter slightly forward or back when it is making the noise?

 

5/6/R are out on an extension shaft by themselves, they could have a tolerance/shimming problem if not rebuilt properly.

The Synchros just lock the gear to the shaft and don't spin any differently when engaged, then when not engaged.

Did you put in a new clutch and/or resurfaced flywheel with the T56? Since both 5 and 6 are overdrive gears, they put alot more TQ on the clutch trying to turn them. Any clutch slippage will show-up in the overdrive gears, if not during hard releases.

 

i just took it for another test drive today and 5th only does it at around 45mph the faster the quieter, 6th does it when i'm not on the gas and has a slight vibration.

 

How many miles on the T56 ? (assuming it's used?) It sounds like the 5/6/R extension is not shimmed correctly, or the 5/6 driven gear is loose on it's splines. If the driven gear is loose, it can/will eventually shread the splines on the mainshaft, and you'll loose both 5&6.

You can check the 5/6/R shimming without opening up the trans, but you have to pull the trans and get a 2' piece of metric allthread to thread through the front plate of the transmission..

http://www.eecis.udel.edu/~davis/z28...e/102_7966.jpg

 

thanks for the link. what are the chances of a used tranny having that problem? when i bought it i was told it had about 79000 miles.

 

Chances are slim, but I've seen just about everything. Could you tell if it was rebuilt before? Telltale signs are excess RTV seepage around the front plate and tailhousings, where the bolt to the center case. Sadly it seems that the backyard-builder causes the most problems on T56s..

 

no from what it seemed like when i had it out this transmission didnt have any kind of slipage of any sort, no silicone either. I did see a little rectangular metal behind a bolt with some writings on it, kind of like a dog name tag. It was green i think this transmission might have been opened and there was also a sticker on the side of it that said something like "if you have problems do not attempt to disamble, please take to the service shop" or something like that.

I really appreciate all your help.