clutch/tranny problem/question

[zredbaron]

BACKGROUND:

 

Took an 82 5spd to a local tranny shop to be rebuilt (replaced all synchros, a couple bearings). I get it back, and I can't downshift into 1st (unless 5mph or slower), can't shift into 2nd if I left 1st above say, 3000 rpms, and can't downshift into 2nd unless at a very slow speed.

 

I take my car to them, they call me back and say it was my clutch. I hear the explanation, but my common sense asks "wouldnt the clutch take out ALL the gears, not just the lower ones?"

 

the clutch, a centerforce dual friction purchased via MSA, had perhaps 15k miles on it. i bought a new clutch (which they recommended NOT be a centerforce; they claim the problem i was having was not uncommon for centerforces). i bought a centerforce again (i always liked it).

 

 

NOW:

 

They put in the new clutch, seemed fine. It didn't shift effortlessly, but night and day compared to before. The problem has returned: can't downshift into 1st unless under 5mph, shifting from 1st to 2nd sucks.

 

Other pertinent information: the tranny/clutch has maybe 1500 miles since rebuild. 4.375 rear with quiaffe behind tranny. the car has seen its first few autox events (4 events + 3 schools) since the rebuild/clutch replace. i autox'd on street tires, so I broke the rear wheels loose all the time. i found the transmission fluid level to be quite low after my last school (hardest autox action it had seen), which was when i first noticed the problem return, at the end of the day, i had a problem getting into 2nd off of a start.

 

 

So, after writing my novel, I ask my questions:

 

Could my clutch be responsible for these symptoms?

Could the low oil be responsible?

Is my local tranny shop incompetent?

[Cruez]

Almost sounds like a syncho...

 

1st gear is a little more apt not to want to go in gear at higher speeds, but 5 mph is not much...

[JMortensen]

Sounds like a synchro to me too. Or clutch hydraulics, like the clutch won't totally disengage because the throwout bearing isn't being pushed far enough into the pp (because you have a bad clutch master or slave or something like that).

 

Did they explain to you how the Centerforce clutch was causing the shifting problems? Was it not letting go of the flywheel or pp or something? Because once you push the clutch in assuming everything hydraulic is working correctly the clutch shouldn't have anything to do with how the car shifts at all.

 

Clutch issues can be tough to diagnose over the net, but blaming the CF clutch doesn't sound right to me. Not a fan of CF clutches at all, but I've never heard of them causing hard shifting unless the hydraulics was not up to snuff.

 

Not enough oil is definitely a problem. Rectify that then start in on the other stuff.

[rudypoochris]

Intresting. How hard were you using the synchros? What gear oil are you using? Were you double de-clutch when entering 1st or second? Do you heel toe?

[zredbaron]

Jon,

 

If it were a hydraulic problem, wouldn't it make all gears difficult to get into, not just the low ones?

 

 

 

Intresting. How hard were you using the synchros? What gear oil are you using? Were you double de-clutch when entering 1st or second? Do you heel toe?

 

Not sure what you mean by 'how hard were you using the synchros'...could you please elaborate?

 

Gear oil: Valvoline Synthetic Blend, 80W-90, I believe.

 

Double-clutch, never.

 

Heel-toe, never.

[Idnevno]

It is probably going to be an internal problem inside of the transmission especially when you said the level was low. My first guess is that the synchros might not have all been changed and if so you could have warped or hurt one by being run low on oil. I would also wonder if they checked the shift rods for straightness?? If they are not straight then they tend to bind where they run through the case and not want to go into gear. If you want to pull it out or even bring the car to me i would be happy to break open the trans. and take a peek at it for you and then go from there. We are located maybe 30 miles away from ya i think, not to sure though.

 

-Dave

http://www.CreationZ.biz

[rudypoochris]

What I ment by "how hard are you using the synchros" i ment, are you taking 1st or 2nd at highspeeds with out matching the speed of the gears inside the trans to the output shaft speed. What rpm would you be idealy at after entering 1st or 2nd if the synchros worked fine?

 

BTW: You might try something in the 50 to 60 weight range for oil. 80w seems kind of heavy to me. Alot of people have had alot of success by simply changing the oil.

[zredbaron]

ah, i see. to answer your question:

 

shifting first to second, at the moment, isnt really a problem if i am driving casually (i.e. behind a minivan). if i am accellerating, i.e. adequate pedal, but not max accell, and take first above say 3500 rpms, then it takes about 1.5-2 seconds to slip into second. again, downshifting from second to first is nearly impossible unless under 5-10 mph.

 

ideally, i should be able to floor 1st until the wheels break loose (4k-5k rpm?), or if not floored, i should be able to take the rpms to 5k-6k and shift into 2nd. both scenarios should shift quickly -- i had this a few hundred miles ago.

[Idnevno]

I totally agree, you should be able to to shift very smoothly almost no matter what as long as the synchros are good, if the synchros are not good, then you would probably grind gears going in, or the shifter would have a tendency to pop out of gear under load, or sometimes it makes it extremely difficult to shift. You may also have a problem with the pilot bushing did you put a new one in??

[JMortensen]

The gaps between ratios are biggest in the lower gears so the synchros have to work harder on the lower gears. When accelerating from 1st to 2nd the engine you push in the clutch, let off the gas, and while you're shifting the gears naturally want to slow down to the correct speed to hit 2nd. Downshifting from 2nd to 1st is the hardest shift you can make because the synchro has to bring the first gear cluster up to a speed much faster than it was going. So decel is a lot harder on the synchro than accel. This is why heel/toe is SO important.

 

If the clutch is dragging a bit the synchros might not be able to overcome that extra bit of resistance, which is why I suggested that the hydraulics might be an issue. When my hydraulics went out (immediately after installing a stiffer than stock clutch) I had a very hard time getting the car into first and it would grind into 2nd, but after that it felt reasonably normal, but it just felt like the clutch pedal didn't have quite enough resistance. It deteriorated quickly and was pretty much undriveable with 3 days though.

 

Sounds to me more and more like the synchros might have been damaged due to lack of fluid. I'd suggest something other than what is available at your local auto parts store. Try some SWEPCO 201 or some BG Synchroshift or Amsoil or something else. A really high quality lube makes a big difference.

[zredbaron]

thanks, for all the great feedback, guys.

 

jon,

as far as the hydraulics go, both the slave and master have been replaced with brand new ones within the last two years, so that shouldn't be an issue. i bet you're right that the low oil damaged the synchros somehow. i hate myself.

 

btw - i forgot to mention that the problems aren't consistent in magnatude...on some days the problematic shifting isn't as bad as others.

 

weird.

[rudypoochris]

Cant hurt to change the gear oil... Try double declutching or heel toe (id start with double declutching if you have never done heel toe). My explorer redlines 1st at 35mph, but the synchro lets it in at 25mph, if I double clutch I can get it in a 35mph easy. But ya, one really shouldnt ever have a problem shifting up if their tranny is healthy, shifting into 1st and even second at times is another thing.

[technicalninja]

I would look for something causing drag between the engine and the transmission which basically results in clutch performance like a user is only depressing clutch half way.

Clutch not fully dis-engaging (poorly designed PP)

Warped or too thick disc (very rare)

Sticking pilot bearing (very common)

Mis-alignment of engine-transmission (missing dowel or pin at bell housing)

Lack of travel in clutch hydralics (probably not in your case)

Bent/damaged clutch release fork (creates lack of travel)

Improper TOB carrier (probably not in your case)

Improper friction surface height. IE flywheel needs step or flywheel has been cut to much (only seen this once on a Nissan truck but it did effect disengagement).

 

I would lean towards the pilot bushing first. A common misconception is that the pilot needs no lubrication. They are sintered bronze and require "oiling" by placing bushing on your thumb one open end down against thumb, filling the interior with common engine oil until totally full, and slowly apply your other thumb to top pressing oil through bushing. You will actually be able to see oil weep through the walls of the bushing. drain excess oil out of bushing and wipe or blow off. you should not be able to see liquid oil on bushing at install, you are "infusing" oil throughout walls of bushing. I use a wooden dowel to install bushing in crank to keep from mushrooming end. I have used a properly sized socket before and most of the time it worked OK but sometimes it would "ding" the end of bushing. My wooden dowel has never dinged a bushing. "oil" bushing slowly as I once split one by being to hasty- suprised the dog out of me.

A slightly damaged pilot might "fix" itself every now and then causing your inconsistent results.

 

Another minor possibility is the step in the flywheel. Yes there is a minor step. Years ago I verified the step by going out to Courtesy Nissan in Dallas and measuring all the new 280Z/ZX flywheels that they had in stock. .006 inch was what I measured. I fully believe that most clutches will work fine on a totally flat flywheel as .006 in is a very small amount and could easily be accounted for in normal clutch wear but a friend of mine (375 HP turbo using standard Nissan trans) who drag raced extensively could not get a clutch to last with out a step in the flywheel and he increased his step to .015 as I remember. His problem was different than yours- he was killing clutches; not having trouble shifting.

I also had a customer with a 350,000 mile Nissan truck in which his flywheel had been turned to much moving clutch closer to the engine which caused hard shifting due to lack of travel to disengage clutch. This is the only vehicle I have ever seen this on (20+ years professional import tech). very wierd and hard to diagnose. I had tranny out of truck more than once to find this. Shortly after the clutch/flywheel fiasco his truck started breaking headbolts from age/fatigue and he finially took my advice and replaced it with a newer Nissan truck.

 

The low oil level you described is not good- If the tranny shop did the install shame on them!. I would drain oil into clean pan and really look at oil for debris. Nearly every tranny that I have found problems with had crap in the oil. After draining trans stick your finger into drain hole and feel around floor of case (that you can get to) for debris that didn't come out with oil. Any of the oils mentioned in earlier posts should allow tranny to shift fine (including what you think is in it now). Some of the special oils can smooth tranny operation (and lower tempatures-important for track use) but none of them will overcome an actual problem

 

Hope this helps

Rick

[rudypoochris]

If it is debris you might want to hop on the supermagnet trian that has been in a few threads recently. From my experience with a ford t-5 (so it may be different) with a king cobra clutch (not CF!) they specifically say not to lubricate the pilot more than it already is, infact they say to remove excess. Then again my pilot was not bronze like yours.