Noisy transmission diagnosis

P man

Keister Bunny
Staff Member
Supporting Member
Joined
Apr 11, 2021
Messages
4,617
Location
Washougal Wa
Friend of ours has a 2001 4.0 manual transmission. She brought it to me and said it is very noisy especially in 3rd gear when you let off the gas.

I test drive and verify it is silky smooth going down the road but the transmission is very growly. Once you let off the gas it makes loud noise from below (can't pinpoint where) but as soon as you apply the gas it goes away.

I did my inspection and see nothing obvious. The rear diff has been leaking as well as the transmission for an unknown period of time. My first thought is low fluid my second thought is u joints.

Sound about right? Just to be clear this is noise but no vibrations of any kind. I'm wondering if she ran the trans out of oil possibly? Thanks in advance
 
Rear pinion bearing possibly?

I'm going to check that seems to be a common issue. Question though. I grabbed the rear driveline and checked for play and could not detect anything abnormal. How would one diagnose a pinion bearing issue? I'm thinking I will pull the diff cover just to inspect.