Manual Tranny ?'s

[smoove2022]

Hey,

 

Just got my first truck a 1993 silverado over the weekend. It's a 2wd short bed/reg cab 4.3v6 with a 5 speed manual transmission. On the trip home I was noticing the trans was making a crunch noise while engaging the forward gears. The noise seemed to be more pronounced and lasts longer when shifting while the engine is revved high. The guy I bought it from was saying it was the throwout bearing? But I am unfamiliar with manual transmissions. Does this sound like a throwout bearing? The truck has quite a few miles on it (222k) So I am planning on putting a new clutch set in soon. Are there any good websites out there that detail clutch replacing? Will I need any special tools? Does Zoom make a decent oem replacement clutch? They seem to make the least expensive one. Also, what transmission is in my truck?

[citydriver]

Welcome to the site...

 

Sounds like it could be the throw-out(release) bearing...especially if it gets louder when you apply pressure to th clutch pedal....replacement of the clutch assembly is somewhat staight forwrd..especially on a 2wd...a Haynes or Chiltons manual from your local auto-parts store (about $20) that explains the procedure pretty well....

[PFarkas]

With the information given, it doesn't sound to me as though it's the throw out bearing.

 

The throw-out bearing engages the pressure plate in the same manner when using the clutch to select forward and reverse gears. If the problem is with the throw out bearing, the noise should be observed when using the clutch at any vehicle speed with the motor running, even when the vehicle is stopped and the engine at idle or high RPM.

 

Knowing exactly when in the sequence of selecting gears, and under what circumstances the gears are being selected, the noise is heard would go a long way to getting a clue as to what the problem is.

 

 

However, with 222k miles on a transmission, it wouldn't be unreasonable to suspect the synchro bands. I like the synchros better than the throw-out bearing because the original poster said "when shifting while the engine is revved high", and not "when I step on the clutch". The greater the disparity between appropriate the speed of the input shaft and the speed of the output for a given gear being selected, the more the synchros have to work.

 

The problem could also be that the pressure plate isn't being fully disengaged from the clutch plate when the clutch pedal is being applied. This could result from the throw-out bearing being worn, the pressure plate leaves being worn (where they contact the throw-out bearing), and the fly-wheel being too thin and not properly shimmed out from the crank. All of these conditions would be resolved with the proper installation of a new clutch set (pilot bearing, machining the flywheel and shimming as necessary, clutch disk, pressure plate, throw-out bearing).

 

 

Smoove, aside from the number of miles on the truck, why are you considering installing a new clutch set? Is it slipping? Has it ever been changed?

 

I replaced mine at 85,000 miles because the pilot bearing was shot and I wasn't about to take the transmission out to change that and NOT change the clutch set. At 85,000 miles, the clutch still had plenty of life left in it, and the throw out bearing was still fine. I didn't make any measurements on the parts, but comparing the old parts with the new I would guess that I could have gotten another 50k miles out of my old clutch.

 

Of course, I don't do as many hole-shots as I used to, so maybe I could have gone even longer...

[Colorado Kid]

My '91 V-6 5speed still had the original clutch at 215K when I sold it, and I wasn't about to replace it unless it gave me a reason.

 

I too tend to think your syncros aren't keeping up. The tranny you have is the NV3500. It calls for an expensive and tranny fluid called Syncromesh or GLS. If the wrong fluid is used in it the synchros are noisy and the shift feel is lousy. A drain and fill with the proper fluid (Penzoil Sycromesh, get it at Autozone) might just improve it dramatically, and is way less work than a clutch or throwout bearing. (Any job that involves seperating the engine and tranny is a CHORE!)

[Wingnut]

Only thing I can add here, is in answer to the tool question.

 

Yes, you will need a special tool. It's basically a big pin, or shaft that centers the pressure plate/clutch assembly on the motor when you install it. Most auto parts stores have them for borrowing.

 

I have also heard that some clutch replacement kits are coming with plastic throw-away jobbers that would negate my post entirely. I havn't done a clutch in about 6 years, so I don't know whether or not this is true.

[PFarkas]

I EMPHATICLY agree with Wingnut's tool suggestion.

 

For every clutch disk there is available a matching tool.

 

My experience has been that if you buy a clutch kit, the alignment tool is often bundled with the parts.

 

In any event, do not even consider attempting the job without the correct alignment tool. The throw-away ones that I have used have worked fine for me. I can't remember paying more than $5 for one.

 

Make sure that the alignment tool fits the clutch disk you are installing as well as the one that you are replacing. It's an easy way to find out if you were sold the wrong clutch disk without taking the pressure plate off of the flywheel (and believe me, you only need to find out that you SHOULD have checked that ONCE to have the lesson stick).

 

Clutch life varies greatly and depends almost entirely on driver technique, experience, and skill. The clutches in my vehicles last a LOT longer now than when I was 16. I expect that when I'm 50, they'll last even longer.

 

One early sign of clutch failure is slippage. The clutch will begin slipping when a lot of throttle is applied in high gears. As catastrophic clutch death approaches, you'll find that it takes less throttle to induce slippage in the highest gears. My experience has been that when you start observing slippage in 3rd with modest throttle, you'll probably need some help getting the vehicle home if you don't change it within 300 miles.

[sjspor]

A bad throwout bearing will grind, or whine and rumble when you push the clutch in, if you have the tranny with the creeper gear, the first gear you won't use, then for sure that tranny is shot. I can't say about the light duty tranny. Usually if the syncho's are bad it will be a bear to shift, or it will pop out of gear.

 

Anything with over 200K, I just wait for the bang and then decide what to do.

[smoove2022]

WOW guys! Thanks a ton for the replies (or should I say 1/2 ton )

 

The grind is comming only while letting off the clutch pedal for engaging a gear. So when starting from a stop for example - The stick is in the 1st gear position and the clutch pedal is depressed (truck is still). As I let out the clutch pedal and the truck starts to move, it will grind untill the gear is completely engaged and my foot is off the pedal. Unless I heel-and-toe it just right and apply only light throttle, then it won't grind too bad. At no other point in the transmission operation does it grind. I feel no shaking, nor do I hear any squeeking or other strange sounds.

 

I am definately going to pick up some of the syncro mesh gear lube and give that a shot before tearing the tranny apart.

 

Also, at what point should the clutch engage? I am feeling it engage when at the very end of the pedal travel. Is this right? Is this a way to determine if my clutch is wearing? In most of the other manual trans vehicles I have driven (all were cars, not trucks) the clutch would engage sooner in the pedal travel... Not that that has anything to do with anything but it just feels different than I am used to.

 

Thanks again for all of your input!! You guys rock!!

[PFarkas]

With that information, specificly that you don't hear any sort of grind except when you are releasing pressure on the clutch pedal, I think the throw-out bearing is the most likely suspect, followed by the pilot bearing.

 

If the problem is the result of a bad throw-out or pilot bearing, no amount of changing fluid in the transmission will resolve it. However, changing the trans-fluid is still a good idea if you don't know how long it has been in there.

 

Either bearing (throw-out or pilot) requires nearly the same amount of labor to replace - you have to separate the transmission from the motor to get at either of them.

 

While it is possible to change the throw-out bearing without removing the pressure plate and clutch disk (which you pretty much must do in order to get to and replace the pilot bearing), I think that if any of us found out that you replaced the throw-out bearing and didn't change the rest of the clutch maintenance items, we'd have to send you to a shrink and possibly beat you.

 

Doing this job on a two-wheel drive truck shouldn't be too bad, assuming you have a dry place to work and are comfortable with removing and handling heavy parts.

 

Here's a link to an overview of the assembly, which may give you a better idea of what you may be getting into.

 

 

As far as "when should the clutch engage", many people will tell you that the clutch should start to engage at about 25% of pedal travel and be completely engaged at 50% of pedal travel. In cable actuated clutches, this can be adjusted as the clutch disk wears, however in a hydraulic clutch, this is not operater adjustable (it adjusts itself the same way that disk brakes adjust themselves - by allowing fluid from the reservoir to enter the system as additional fluid is demanded by the slave cylinder).

 

If you need to press the clutch pedal very far in order for things to work, that usually indicates a worn clutch disk.

 

 

With the indicators you've given pointing to a failing throw-out bearing and a worn clutch disk, I think that sjspor's advice of "just wait for the bang and then decide what to do" is probably best, except I don't think you're likely to experience a "bang".

 

I'd wait until either the clutch begins to slip, or the noise becomes more frequent and too irritating to put up with, at which point I'd replace the pilot bearing, clutch disk, pressure plate, and throw out bearing. I'd also replace the clutch fluid and inspect the slave cylinder and replace or repair it if the seals look questionable.

 

 

Good Luck!

[C1500]

I believe your problem is the input shaft bearing is going bad, not the throwout bearing. I have the same noise in mine. In my case the noise started about 3 years ago & slowly got worse for about three months and has stayed about the same since. I get the "chattering" sound in first gear every time, and half the time in 2nd gear. If I lug the engine in the upper gears I can get it to do it in them too. the noise is annoying but it hasn't caused any problems. As far as your clutch pedal, If it is engaging at the end of the pedal travel I would say it is working properly, they are not adjustable. you should feel pressure as soon as you press the pedal, if not you may need fluid in the master cylinder. My "release cylinder" is leaking and I need to fill the the fluid about once a week.

 

I have 174,000 miles on mine.

 

 

Does anyone know where to get a repair manual for the NV3500? Since I have to repair the clutch, I would like to repair the noise too.

[Jerther]

I EMPHATICLY agree with Wingnut's tool suggestion.

 

For every clutch disk there is available a matching tool.

 

My experience has been that if you buy a clutch kit, the alignment tool is often bundled with the parts. 

 

In any event, do not even consider attempting the job without the correct alignment tool.  The throw-away ones that I have used have worked fine for me.  I can't remember paying more than $5 for one.

 

Make sure that the alignment tool fits the clutch disk you are installing as well as the one that you are replacing.  It's an easy way to find out if you were sold the wrong clutch disk without taking the pressure plate off of the flywheel (and believe me, you only need to find out that you SHOULD have checked that ONCE to have the lesson stick).

 

 

<{POST_SNAPBACK}>

 

 

 

awww, 5$!?!?!? I replaced my engine last summer.. and I remember it took like half a day to put it back with the tranny, just by guessing. that was terrible