Help with rearend after rebuild and 3.73s

Bigstang1

Founding Member
Aug 28, 2002
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16
Massachusettes
I just put in my 3.73s today (i work at a ford dealership with alot of mustang guys) and i put in all new bearings and new clutches. Got it all back together and it doesnt whine or hum or anything and feels great going straight, but when i go around corners , there is a horrible ratcheting poping grinding sound. Its pretty loud and u can feel it through the car. Now the techs that helped me put it in didnt say anytthing about soaking the clutches in friction modifier and we put them in dry. is this causing the problem? I did put the friction modifier in the fluid in the rear end however. any idea what this could be? i was told to drive it for a few days and see if the cluthes wear in and it stops. WE set the pinion depth and backlash perfect and the pattern came out pretty mint and it makes no noise straight so i doubt its the actuall gears. any ideas thanks
 
The additive is a friction modifier, it is made of a smelly, sticky formula. I heard you say you set the backlash and everything correct, and that the clutch packs where new. I was just curious if you took a gauge to the old clutch pack and reinstalled the same amount. Some of those kits are universal and was just making sure you didn't put them in to "tight". I would imagine if you did soak the clutchs that the effect would be opposite until they became obsorbed by the modifier. That is they would not work as well. I could be wrong, but I do remember the friction modifier being sticky and helping grab.

EDIT: What shape where the spider gears in?
 
It would have to be either the spider gears or clutch pack. I know you said the guys at Ford said it will fix itself. Well, I would think that if you installed the clutch pack to tightly (to thick or to many clutches from universal kit.) then just giving it time to go away would just eventually rub off all the imperfections in the clutches that allow it to grab, ultimately defeating the purpose of the replacement in the first place and you would be back to one will spin. Someone correct me if I'm worng?????
 
The car just sat outside for a few hours after the ride home from work and i just got back from a ride. Problem is totally gone. I guess they just needed to soak in the friction modified diff fluid. thanks for the replys guys and hopefully this will help somone else
 
my$100project said:
The additive is a friction modifier, it is made of a smelly, sticky formula. I heard you say you set the backlash and everything correct, and that the clutch packs where new. I was just curious if you took a gauge to the old clutch pack and reinstalled the same amount. Some of those kits are universal and was just making sure you didn't put them in to "tight". I would imagine if you did soak the clutchs that the effect would be opposite until they became obsorbed by the modifier. That is they would not work as well. I could be wrong, but I do remember the friction modifier being sticky and helping grab.

EDIT: What shape where the spider gears in?

I'm pretty sure friction modifier is slippery to prevent the clutchs from chattering.
 
maverick0716 said:
A common trick to make the trac-lok unit grab better is to install extra clutch packs. This is good for performance, but it probably would make it chatter more, and they'd also wear out quicker.
Properly done, you would never have chatter and durability would also be improved. The sheer load is being supported by 4 discs per side versus the 3 found in stock configuration.