Rear howl, slipping rear end? Stock gears.

supergoat · Feb 10, 2007

Car has 19k miles on it.

Sometimes when I punch it in 2nd or so, the car will pull very nice like it's supposed to. But other times it will just kind of go, feels like the clutch is slipping, but it's not. The clutch grabs extremely well. But all the power is not there. It's pulls forward a bit then you can slowly feel/hear the power come on like it's "catching up".

And last night I noticed a howling coming from my rear and a little noise at low speed turns. The gears are factory stock.

It's still under warranty, but I'm 3.5hrs away from home, it's the weekend AND there are no Ford dealers by me anyway, and want to make sure it will make it home, This all started after I was already here, otherwise I would not have taken it on the trip. . Any idea what it could be? I do have the t-lok rear.

sgarlic · Feb 10, 2007

Just drive it home. If something fails on the way, and it's Ford's own fault, they pay for the tow truck, and any associated repairs after it gets there.

Mustang5L5 · Feb 10, 2007

Well rear ends cannot slip. They are physically meshed gears so no slippage can occur.

thomas91169 · Feb 10, 2007

if i recall, the only thing in the rear end that could slip would be the clutch packs in the trac-loc, but that would only make you one-wheel-peel.

Mike97gt · Feb 10, 2007

the differental pinion gears or side gears as many call them can slip and grind away I have seen some where the teeth were worn or ground right off of them. It's possible that this happend and the metal bits ruined the bearings causing the howling you are now hearing.

I would think you would have noticed more than just a bit of power loss if this happend

LaserRed01GT · Feb 11, 2007

The Trak-Lok rear ends have clutches much like the clutch for the transmission. The Trak-Lok rear can absolutely slip when the clutches are worn.

There is also a S-Spring(differential clutch spring) that preloads the clutches and holds them up against the side gears. This spring can wear and become weak allowing the clutches to slip. There is an upgraded heavy duty s-spring made by Ford.

Ford Part# F3TZ4214A

Mustang5L5 · Feb 11, 2007

LaserRed01GT said:
The Trak-Lok rear ends have clutches much like the clutch for the transmission. The Trak-Lok rear can absolutely slip when the clutches are worn.

But that sort of slippage would only occur when one of the rear wheels spin. It would result in a one-wheel peel because the clutches would not transfer power to the other wheel.

In a normal state, with both wheels gripping the pavement and not slipping, it would be inpossible for the rear end to slip because the clutches would not be being used in that situation.

supergoat · Feb 11, 2007

Thanks for the replies guys. It made it home just fine. Going to the dealer tomorrow. The howl actually got quieter as I made it close to home so we'll see what they say.

Red2000GT · Feb 11, 2007

Let us know what it was,my guess is a bearing packed it in and may have caused the trac-lok to slip. You'll lose a little "acceleration power" as the one tire breaks loose then grabs again as the lok kicks back in.

supergoat · Feb 11, 2007

Well if anything IS indeed wrong in the rear end and they have to take it apart. I'll get them to install a set FRPP gears for me since the labor would be covered by warranty anyway.

Mustang5L5 · Feb 11, 2007

I honestly think the problem is elsewhere and not in the rear end

LaserRed01GT · Feb 11, 2007

Mustang5L5 said:
But that sort of slippage would only occur when one of the rear wheels spin. It would result in a one-wheel peel because the clutches would not transfer power to the other wheel.

In a normal state, with both wheels gripping the pavement and not slipping, it would be inpossible for the rear end to slip because the clutches would not be being used in that situation.

The rear end can slip just as if the transmission clutch were slipping. It's not mechanically locked at all. Trust me I've driven a bunch and rebuilt even more. The only way to mechanically lock the axles to the carrier case is with a locker or spool.

There are splined steel discs that are stacked with the non-splined friction discs on the side gears. The differential case itself does not transfer power to the axles, the clutches transfer power to the axles by way of the side gears. If the friction discs get worn, the rear end can slip and it will feel just like the manual transmission clutch is going out.

This guy should first make sure his clutch isn't slipping and make sure it is adjusted properly, then look to the rear end.

blkhorse · Feb 11, 2007

the axles are mechanically linked to the carrier thru the pinion gears and cross shaft,you may have rebuilt a lot,but you don't understand the operation

LaserRed01GT · Feb 11, 2007

blkhorse said:
the axles are mechanically linked to the carrier thru the pinion gears and cross shaft,you may have rebuilt a lot,but you don't understand the operation

I'm sorry but you are wrong. The primary means of friction between the splines on the axles and the splines on the inner side of the side gears are the splined steel discs. If you were to leave the splined steel discs out or leave the s-spring out your rear end would quickly be destroyed from the free spinning carrier case. That's just the way they work.

blkhorse · Feb 11, 2007

LaserRed01GT said:
I'm sorry but you are wrong. The primary means of friction between the splines on the axles and the splines on the inner side of the side gears are the splined steel discs. If you were to leave the splined steel discs out or leave the s-spring out your rear end would quickly be destroyed from the free spinning carrier case. That's just the way they work.

if you took out the parts you mentioned the rear would destroy itself from the pinion gears and side gear clearance,the posi rear axle is nothing more than an open diff with a preload on the side gears to aid in traction.I have also rebuilt many rear axles over the years,might want to rethink your view on the operation of a rear axle

Mike97gt · Feb 11, 2007

As I said a few posts earlier in this topic the power is transfered through the differential pinion gears the top and bottom gears have a hole that the cross shaft goes through and the side gears are splined to the axles and friction dics plates.

IF the pinion gears are damaged then you can have slippage and this will continue untill the gears are destroyed and the car will not move.

It is somewhat common on 8.8's to damage the diff pinion gears, I have had to rebuild several of them that this has happend too..

In this case i don't think thats the problem because if those gears were damaged then they would rapidly destroy themselfs to the point that the car will not move.

blkhorse · Feb 11, 2007

LaserRed01GT · Feb 11, 2007

Most of the time the side gears and/or the carrier pinion gears will get damaged when the friction or steel discs get worn or damaged, but the rear end will not always just grenade. Sometimes they will hold on for a while. And like I said, it can feel just like a M/T clutch slipping. The pinion shaft doesn't just hold the pinion gears in place, the pinion gears actually rotate on the pinion shaft.

With that being said, these 8.8's don;t usually give up the pinion gears or side gears, it's usually a disc or axle problem, and if he has a rear-end problem that is likely the source.

blkhorse · Feb 11, 2007

LaserRed01GT · Feb 11, 2007

blkhorse said:

I know, it's hard to grasp reality.

Rear howl, slipping rear end? Stock gears.

supergoat

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