Transmission rumble

[94Blue]

Hi all, I'm new to this forum and this is the first time posting. Just recently bought a 94 Bronco with the 302 and 5 speed manual transmission. It has about 120k miles on it, both the original engine and transmission.

When I shift the truck into 5th gear, at about 55 mph, there is a low grumble noise. It is most noticable between 55 - 70 mph. It does not seem to affect acceleration too much. Has anyone experienced this issue? If so, what have you done about it? I've talked to some different people, most people say that 5th gears sounds like it is going and I should change my transmission fluid. Doesn't seem like a problem and easy enough to do, but then a few people told me that it is actually bad to change/add the transmission fluid on a vehicle with over 100k if it has never been done. Being that I just bought it, I'm not sure if it has been done.

Any advice will be appreciated. Also, sorry if there has been a topic similar to this posted, I was looking but couldn't find it. Again, still getting used to this forum.

Thanks

 

[miesk5]

yo 94BLUE,

WELCOME!

I'd replace fluid since it is a manual tranny.

Ford's Normal Use schedule shows Change manual transmission oil @ 60,000 miles

Here is the 96 schedule; http://www.motorcraftservice.com/pubs/content/~WOTBRO/~MUS~LEN/41/96bromg1e.pdf

Read this, esp 2nd page on 5th gear about the synchro

M5OD 5 Speed Transmission Overview

Source: by Mike W @ http://www.rsgear.com/articles/1993_11.pdf

or it's the output shaft bearing

M5OD Parts Break-Out Diagram w/ Nomenclature; shows Shift Lever w/Ford part number E8TZ-7210-R SHAFT - GEAR CHANGE & shows ****, but no PN; MIESK5 NOTE; **** is pressed-on

@ http://www.partesymas.com/catalogos/estandar/M5R2.pdf

M5OD Preventative Measure; Those of you who own Ford full size or small size trucks with the M5OD Mazda design 5 speed manual transmission should have the rubber shift cover plugs resealed at your earliest possible convenience. A common occurrence with this model transmission is the rubber plugs shrinking over time and allowing **** oil to leak out of the transmission. This occurs while the vehicle is in operation, so there is less of a tendency for a puddle to develop when the vehicle is sitting parked. The result to the transmission is a lack of lubrication and damage to some very expensive gears and bearings.

Source: by DRW Transmission Specialties, Inc.

 

[94Blue]

Thank you for the information. Very useful stuff. I will try the fluid this weekend, see what it does and let you know what happens.