'01 DRIVETRAIN SLACK??

[YELL-OSNAKE]

I would tend to believe my clunk seems to come from the rear end....After stating earlier in this post...leave car in neutral and running, apply e-brake, have someone...preferably you look at the drive shaft. have the person push clutch to floor and engage gear...don't let out clutch, just engage 1st....my drive shaft moves maybe 1/4 turn...play to me seems to be in the rear-end...I would also agree the clutch has a moderate amt of grab to turn the drive shaft...with the pedal to the floor, but I believe all cars will do this....go jack the rear end of any of you buddies cars up...put in first with clutch to floor, wheels will start moving with no load. Same is happening here...the drive line gets "preloaded"....which really is a good thing...., but there is too much backlash, or pinion depth not correct.......,could also be sloppy spline mating on the half-shafts, but after hearing from COBRA-R 's post...I'm starting to believe it's the gear. Maybe ford has bad specifications for backlash....:shrug:

P.S. brad65ford...check your car out with the drive shaft thing and see it you get the 1/4 turn movement............I would also disagree with your friend...the input shaft of the tranny is not ALWAYS turning... when you push the clutch in it allows the shaft to stop turning... the clutch disengages the engine from the tranny, and at a dead stop, with the clutch in , the shaft doesn't turn. Try my method of drive shaft above...after you get the clunk...shift thru all gears, going back into first.....no clunk now, right......the rear-end slack was already pre-loaded...so no clunk. try it.

 

[wildosvt]

My car doesnt do it anymore after I had the trans fixed.It used to do it often,But when I stop I dont do the (holding clutch in) back and forth from 1st to 2nd either.I used to but just worked out of my driving style.After I have read what everone posted I thought alot about this and it is wierd maybe it "is" coming from both ends.

 

[Daniel Moran]

I spoke today with the shop foreman of my SVT dealer, Kayser Ford in Madison, WI. He said he has 24 years experience working on Ford transmissions and drivelines. I described the neutral into first gear clunk and he said it was a real common characteristic of all stick Fords not just Cobras. He said it's due to "spindown time" of the trans input shaft and that a few more seconds of clutch engagement prior to sliding into first (or going into second before going into first) is the way to avoid the noise. He said "it's just the nature of the beast". That's unfortunate because I've been driving manual trans musclecars of numerous makes since 1967 and have never experienced this. Calling 1(800)392-FORD seems to have gotten a good response to my complaint so far, so I'd recommend you other concerned Cobra owners at least call and be heard.

 

[brad65ford]

Thank you Daniel Moran, I guess the spin down of the input shaft is what we are dealing with. Which made sense to me when it was explained by my friend. I have tried waiting a few seconds after the clutch pedal is to the floor and then put it in to first and it still get the clunck. Sh*t is still spinning in the trans! Ya know what I mean?:shrug:

 

[brianm]

I really think there's two separate issues causing the clunk. When I first started trying to diagnose the cause of my clunk, I found that holding the clutch down for a moment to let the input shaft spin down eliminated the clunk when shifting into first. The input shaft alone though isn't the reason you're hearing the clunk because if so, every other manual transmission car would be prone to the same problem. This combined with some other source of driveline slack is causing it.

I, however, don't think it's the rear end. Mine does it before and after the 4.10 gear change, and since I did the change myself I'm confident the backlash is within spec.

I think the source of the excessive backlash is in the transmission itself. While I was under the car, I checked to see how much freeplay there was on the output shaft of the transmission while the car was in various gears. I found that I could move the output shaft at least 3/4" from side to side. I couldn't find a specification for transmission backlash in the shop manual, and it didn't look as though it's even adjustable when rebuilding it, but 3/4" would seem to be excessive to me.

My theory is, when the transmission engages first gear, the spin on the input shaft takes up the freeplay in the output shaft, which from the momentum of the driveshaft, causes the pinion to hit the ring gear harder than usual, thus giving the clunk that eminates from the rear end. This would seem to be supported by those who have eliminated the problem just by replacing the transmission.

Then again, I could be totally off.

Brian

 

[Steve]

If the T56 in other cars is not doing this, we can likely eliminate this as a problem. Also, the T56 in the 03 seems to have the same clunk that we have with our T45 or 3650's (same thing, really). When I shift my car into first after neutral, the car clunks but doesn't jump at all (even with brakes off). From the sound of the clunk, I would think it would cause a noticeable motion. Does this happen on pre-98 cobras or 99+ GT's. I am inclined to think it is the IRS. Something in the IRS is not lining up properly with the trans. Then the spindown time or motion of fluid may cause the clunk.

I really think it is just a backlash issue however. I have noticed that if I shift into 5th gear while decelerating in 4th, I get the same type of clunk. If I shift to 5th while accelerating, I don't. This makes me think that on the upshift while decelerating, excessive backlash (pinion going from decel to accel) may be evident. I would like to know if anyone else has noticed this. I have only noticed in 4 to 5, but that shift is usually quieter RPM wise than others. I would imagine it exists in all gears.

Steve

 

[mike99]

The drivetrain in my 03 feels a tighter than in the 99 Cobra. When I had 4:10 gears put in my 99 2 years ago it got rid of the rear end clunck. The tolerances from Ford were/are too great and they don't shim the gears properly. After a while, you end up driving the car in a such a way that you avoid the transmission clunk...

 

[pichon244]

I HERE YA

MY 2001 DID THE SAME THING------NO MORE THOUGH-----I REPLACED THE STOCK CLUTCH! THAT THUD IS FROM THAT CRAPPY STOCK CLUTCH. I HAVEN'T MET A 2001 OWNER WHO HASN'T SAID THE SAME THING

 

[Daniel Moran]

Pichon 244, got a few questions. I assume you made no other driveline mods like gears. What type of replacement clutch did you put in? Was the pressure plate replaced? Did Ford do the work? And what killed your factory clutch? If we could nail this thing down to just a clutch there might be hope of getting Ford to pay.

 

[pichon244]

Hey Dan . . .

I actually have 4.10gears, a racing single bore throttle body, fr500 exhaust, high flow x-pipe (bassani), custom superchips chip, & JBA headers----(even though headers are a waste of money)!
As for the clutch----I installed the King Cobra clutch----which is heavy but has greater holding ability than the cheap stock Cobra clutch----and I installed a new pressure plate with my aluminum flywheel. The clutch is definetely the culprit on the 2001. I'm telling you----I have a buddy who replaced his clutch-----because of the same problem----and he hasn't heard that sound again!

 

[Trblmkr]

I've heard the clunk on my '01 as well. However, I normally here it when I'm putting the car into 1st gear while still coasting to a stop.

I have more problems with the clunk when the temps outside drop below 50 degree. On hot summer days, I only hear it at the stop lights as stated above.

When I asked my dealership guys (3 who own Cobra's) they all told me it's normal for the 99 and 01's for the way they have the clutch set up to continue to rotate and make it easier when upshifting on hard acceleration.. BS... I don't know, but I trust these guys...

If there is a bulletin on it... let's get the number and get our babies fixed...

 

[pichon244]

I'm telling you bro . . .

its normal for the clutch on a stock Cobra----but the stock clutch is crappy-----after market clutch is better with no clicking and way better holding power.

 

[SVTNICK]

thud is normal. dont worry..be happy. Its in most stangs since 83..and in all 3 of mine...just driveline slack..sometimes u hear it (usually when shifting into first)..sometimes you dont. Ford can tighten bolts here and there..but its hit or miss...but its a very common "problem".

 

[wildosvt]

Re: I'm telling you bro . . .

Originally posted by pichon244
its normal for the clutch on a stock Cobra----but the stock clutch is crappy-----after market clutch is better with no clicking and way better holding power.

Isnt the stock clutch a centerforce clutch???????:shrug:

 

[pichon244]

the stock clutch . . .

is a centerforce clutch----but not high quality at all.

 

[mechanic66]

......so 1 month later....
you can get rid of the clunk by shifting into 4th FIRST and then shifting into 1st.........dunno why......somebody tried explaining it before but I still don't really understand it.

 

[Steve]

I have found that it does seem to be the bearing spin down as stated above. If I hesitate 1 or 2 seconds after I press in the clutch, but before I shift the tranny, the thud is gone. I makes sense, I guess, that when the pedal is out, the input shaft is spinning at the same RPM as the motor. When you press in the clutch, it takes some time for the assembly to stop rotating.

 

[Lo Pony]

There are many things that contribute to this clunk. Get under the car and rotate the driveshaft. 1/2" of side to side play is normal. I've had 4 of these cars, and they all do it. You just get used to it after a while.

A ex-honda or toyota owner would notice this, because these rear drive mustangs don't have little spindly rubber-band drivetrains. Big heavy flywheels and clutches, steel driveshafts, etc. The clunk usually comes from the stackup of looseness in the transmission, and the axles in the side gears of the differential. The slack between the side gears themselves also contribute. Rarely ever is is slack in the ring and pinion.

Unless you're getting an unusually loud metalling clanging noise or have more than 1/2" of rotational slack at the driveshaft, it's nothing to worry about. Just enjoy.

 

[Coop]

Some clunk is normal, due to drivetrain slack. IMO, what you are hearing is the resulting noise sourced at the differential, as you load up the drive train, radiating a "clunk" back through the drive line and often believed to be tranny or drive shaft noise.

I've setup quite a few gears on the 99 and 01 Cobra's, and a good number of them having been shipped from the factory with excessive ring gear backlash. Ford uses a fixed iron shim. Specs do allow for a range of adjustment, from 0.008" to 0.015", but on those that I dialed in at 0.008" with adjustable carrier bearing shims, the clunk was very minimal, almost non-existent.

Mine is clunk free.


__________________
99 Cobra coupe Xtreme daily driver!
(I do all my own work, including engine, transmission and differential rebuilds)
T-56, built motor w/cams, P&P heads (just to name a few mods)
Still using returnless fuel setup and independent rear!
570rwhp/466tq on only 10.5 psi boost, 93 octane pump gas tune.
Official 1/4 mile: [email protected] 1.81 60' (limited only by the half-shafts and hot weather)
A 10 sec capable car!

A Cobra on the surface, a Viper underneath!

Exterior - larger view || -- Engine-zoom in -- ||Chassis/Suspension

Other stuff (partial list):
T-56 R&R guide tube
T-56 R&R input shaft breakage
Spring cleaning

http://www.svttexas.com

 

[wildosvt]

Mine used to clunk til the 2nd gear fork went bad and I took it in for repair.Now after the trans was rebuilt the clunk is gone...........:thumbsup: