Clutch question.. not slipping but wont hold sitting still?

[AcIdBuRn02ZTS]

Hey guys..

So.. 2 nearly identical trucks.. only difference is rear gear (4.10 vs 3.55). Same 37" rubber... same trans... same clutch kit (luk single mass conversion).

The truck with 3.55s has no problem resting on a grade in gear without using the parking brake. Mine however, will slip the clutch in very slight little bumps (and you can hear the clutch chatter slightly as it does it).

The clutch holds solid under power and has never slipped (only has 5k miles on it or so).. no oil contamination/etc..

So.. what would cause it? I didn't replace hydraulics when I replaced the clutch.. could that be the cause? The other truck has all new hydraulics.

 

[A48WillyzGuy]

Here's a correction for the above post.

I am the owner of said 3.55 geared truck. As stated in my sig, I have a 460 ZF which is lower geared. Overall gearing on mine is a good bit lower than his in first gear. Could this be the reason for his situation?

 

[79jasper]

I don't see gearing really having much to do with it.
Quite the mystery though.
I could see rolling the engine over, but having the clutch slip with the engine off, but not when on is wonky.

Sent from my SAMSUNG-SM-G935A using Tapatalk

 

[snicklas]

Are you 100% sure the clutch is slipping? The only manual transmission I have in the fleet is my 91 Jetta 5 speed. It is a 4 cylinder N/A IDI with fairly high compression. I have a relatively steep driveway..... I can't just leave it gear, any gear, or it will learch down the driveway. It's not the clutch slipping, the engine is being turned over by the transmission. An IDI truck is heavy and can put a lot of force on the driveline.

Here is my driveway to give you an idea.....

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I am standing in the street, you can see the Jetta in the upper left, and the angle of the driveway by looking at the overhead door..... I actually have chocks on the drivers side to keep it where it is.

 

[shawn deere]

Hey guys..

So.. 2 nearly identical trucks.. only difference is rear gear (4.10 vs 3.55). Same 37" rubber... same trans... same clutch kit (luk single mass conversion).

The truck with 3.55s has no problem resting on a grade in gear without using the parking brake. Mine however, will slip the clutch in very slight little bumps (and you can hear the clutch chatter slightly as it does it).

The clutch holds solid under power and has never slipped (only has 5k miles on it or so).. no oil contamination/etc..

So.. what would cause it? I didn't replace hydraulics when I replaced the clutch.. could that be the cause? The other truck has all new hydraulics.

Mine will roll the engine over with 3.55 gears on a grade.
Put her in 4 low and she dont. Lol

 

[AcIdBuRn02ZTS]

Well.. I can actually hear the sound coming from the clutch.. it makes a slight chatter sound and it will roll backwards slightly (like an inch or so at a time).

What gear the trans is in makes a difference as well. In 1st.. it does it but not bad.. any other forward gear and it wont hold at all. Reverse seems to hold ok but will still slip it from time to time.

I'll pop the hood and watch it here in a bit.

 

[riotwarrior]

Chock wheels...set emergency brake

Remove clutch inspection cover

Paint marker, felt pen or grease pen a line on flywheel clutch disk and pressure plate.

Remove chocks release emergency brake amd test...if clutch slips line would not line up any longer.

JM7.3CW Eh!

 

[shawn deere]

A guy could also mark something on the belt under the hood. The gear reduction would be crazy:1 tho

 

[towcat]

have you considered compression bleeding off. that's what happens with the Sulaco. key indicator is when I fire up, it's popping through the intake something fierce for 5 mins or so and then the lifters refil and it's fine again.

 

[Thewespaul]

Could be that one truck has better compression than the other and your truck has less resistance to being turned over

 

[AcIdBuRn02ZTS]

Engine starts easy and runs strong... And again, Everytime this happens, the clutch pops/chatters. I'll see tomorrow if the engine is turning over bit I've had that happen on low compression turbo gas burners... And this doest feel like that.

 

[Macrobb]

Alright... wait a second here.
My truck, with 4.11 gearing and a 5-speed does the same thing in anything but first. Even first, it depends on the steepness of the hill.
It's because the actual force needed to turn the engine over isn't particularly high... except for the air that's being compressed. So the engine turns over a little until the air being compressed creates enough force to stop it, then that pressure bleeds down through the rings. Repeat.

Also, you've got 37" tires. Which, I believe would give it more "leverage"/'"torque" against the engine on a given grade vs smaller stock tires.

Now, maby it *does* have lower compression than the other truck. It doesn't mean that it wouldn't start and run just fine - these engines have compression to spare.
I've found a lot of "engine's shot, won't start" has a lot more to do with glow plugs and injector timing than low compression.
Sure, *too much* leakdown will keep it from starting... but the engine's going to be using a ton of oil due to broken rings before it gets to that point, most likely.

The solution? Fix your E-brake, or install a driveline brake.

 

[IDIBRONCO]

I hope his IDI doesn't have lower compression than the 460 in the other truck.

 

[AcIdBuRn02ZTS]

The other truck doesn't have a 460... It has a zf5 from a 460 which has a much lower first gear.

 

[IDIBRONCO]

Oops! My mistake. Ok. The lower gear ratio can make a difference.