1983 base model, 134K-ish miles

Between 1800 and 2400 rpm it drives like the clutch is slipping with a mind of it's own, anything above 2.5K and it holds just fine. Even dumping the clutch at 4K feels fine without any slip. It doesn't make sense to me that a clutch would slip while fully engaged with a low load, but not slip more consistently with a larger load, even if being dumped.

 

Sounds like a clutch to me. Heres the best test. On the highway if your cruising along,
say at 60 mph in 4th gear, floor it. If you see the rpms going up inconsistent with the
speed, your clutch is slipping.

Dumping the clutch at 4k will always result in some slip so thats not a good test and
its hard to tell if it is slipping or if its your wheels breaking loose or what. The highway
cruise test is pretty accurate because its the highest load you can put on the clutch
short of dumping it. If its gonna slip thats when you will first notice it.

 

+1 ^^^^^^

 

The procedure for testing a clutch that I read in a repair manual decades ago was to:

1. With car idling and foot on brake, press in the clutch pedal.
2. Move shift lever into 5th gear.
3. With foot on brake, slowly release the clutch.

If the clutch grabs enough to stall the engine, then the clutch is "serviceable" (useable).




.

 

it will stall in first no problem. i will try some 2nd, 3rd, and 4th gear pulls on my way home to see if i notice anything odd.

 

I'm baffled... here's a list of the things I tried on the way home:


Semi-harsh launch (twice), 1st & 2nd gear WOT to 7k, 3rd to 75MPH, 4th from 50 to 75MPH... speedo and tach moved in unison for all of these (though in 4th they moved at literally the same angle, by design I assume?)

Upon parking I plopped it in 5th, and with my foot on the brake very slowly let the clutch out. While it did slip some and bogged the engine down, as I would assume, It always stalled it just around half pressure.


When I say it feels like a slipping clutch, I mean more or less the G's I'm experiencing... Random herky jerkyness that doesn't seem to relate to speed, gear, throttle position, or road condition. It ONLY happens between 1500 and 2400 rpm and is annoying as hell!

 

wait. So if you're in say.....4th gear and you let off the gas and it slowly drops to about 1700...it starts to jerk around at random? that's normal if I'm not mistaken.

Does it do that if you're accelerating?

also - get it to that point and just barely touch the gas to keep it at a consistent rpm. it should stop.

 

I know what you mean by the normal bit... but this isn't like that... it's far more pronounced. Not just the touchy throttle. Happens even when I've been cruising at 30 for 2-3 minutes with no traffic/reason to slow down.

 

The street car clutches that have started to fail on me started slipping in 5th on the highway. They always worked fine in lower gears or under hard acceleration

On my racecar a bad or worn clutch will slip on an upshift from 3rd to 4th and then hold okay. No issues on downshifts.

How many miles do you have on the clutch?

Also look for oil/trans lub at the bottom of the bell housing. A leaky rear seal on the engine or a leaky front seal on the trans could put oil on the clutch. This would cause it to slip.

Between a leak or a worn out clutch - I'll take the clutch anyday.

 

I don't think it's the clutch at all... be it fuel or timing or something, it's giving the sensation of the clutch slipping. Unpredictable lurching... but only at the previously mentioned range or RPMs

 

Uh, what your now describing is called bucking and its not unusual for these cars
when running lean or something. I would look into your fuel supply system. Check
the filter, flow and pressure.

Change the filter.

Test the flow by seeing how fast it fills a measured container at the carb.

And if you have a way to test the pressure do that and get back at us.

I'm thinking you have a fuel delivery issue.

 

I will hopefully do that this weekend.