Join Date: Dec 2001
Location: Belleville, Illinois
Thanked 22 Times in 17 Posts
Re: Noisy 4 speed trans. Normal?
Most, if not all, 4-speeds that have a granny low use spur-cut gears for low. By their nature they will make a lot of noise.
The intermediate gears on any modern transmission are helical cut, and should be pretty quiet.
Top gear in (as far as I know) all Jeep transmissions is actually a direct connection between input and output shafts, so the gears are just along for the ride, and the box is quiet.
If the noise is excessive, it almost has to be either a bad input gear or cluster gear, or the bearings that support them. In which case, heavier lube will make it quieter, but if it's the bearings that are bad, they will eventually ruin the gears too.