Okay I've been having problems with my 7.3 IDI (ZF5 4x4, 4" lift 35"s, I believe regeared at 4.10s) not having the power it did a few weeks ago. I thought it was the ebrake stuck, so I replaced that (as in drum hardware and cylinders, I didnt replace the cable but I now know its not sticking). I then thought it was partially my front calipers sticking, replaced those. I got the whole thing put back together and no difference. This is starting to get on my nerves as I've already spent close to 400$ on the brakes and it seems like that wasn't an issue... So here are the symptoms

I used to be able to start from a stand still in second just fine, steadily getting up to 25mph when I'd hit 2500 rpms and shift to third. Now if I start in second it takes much longer to get going and if I put to much throttle on, the rpms will skyrocket to 3000 with no difference in performance from the motor, as if its under a major load (hence my suspecting of the brakes). If I start in first to get it going, it'll go up to around 10-11mph before hitting 2500rpms and I'll shift into second. Once in second It acts pretty much the same trying to get up to 25mph(a little better). Its almost as if Im putting the throttle on while in neutral because the turbo doesnt spool up like its under a load. (It's not quite the same as neutral because i am getting some throttle response just not as much as I had a month ago)

Could it be the clutch pad is "slipping" and therefore not transferring the power to the tranny and drive train properly? I dont even know if this is possible based on how a clutch works.

I checked my K&N airfilter for clogging and poor air flow and it has oil and seems fine. According to my boost gauge my turbo hasn't failed and is still spooling up. It can't be a fuel deliver issue (pump, injectors, etc.) because im still getting the rpms from the motor.

I first noticed this poor performance while hauling my unloaded 4 horse about a month and a half ago. I've hauled the trailer before and had much better results from my truck with it loaded down. Since the problem didn't get a whole lot better after the haul I new it was an issue with the truck, not the trailer.

Any way the only thing i can think of is clutch issues. But as usual you guys are more of the "experts" and will probably bring up something i never even thought of. So let the comments fly! Any and everything welcome cuz I'm at a loss on how to get my old truck back

Thanks in advance guys

 

If the engine speed (rpms) is changing without the vehicle speed changing at the same rate, something is slipping. Since you've got a manual trans, nothing should slip, so that means something is wrong. And it's almost certainly going to be the clutch slipping.

Obviously if the tires are spinning you'll get the same issue, but you can probably tell if that's happening.

And auto trans do slip, that's normal there. But not with a manual.

 

Yep no tire slipping. So it could be the clutch. That was the only thing I could think It'd be...

Thanks

 

Any idea on what I'd be looking at spending for a clutch kit?

 

It amazes me how few people know what a slipping clutch is. But anyways, yes. If your RPM shoot up with no gain in speed, your clutch is cooked and it needs to be replaced.

 

Touche, next time you have a question I'll be sure to point out your lack of knowledge.

After more diagnosing I'd get up to third gear drop her into second and there is a delay in the rpm response.... definitely the clutch.

Thanks for the help. What kind of a kit/what should be included? Price?

 

Sorry if I came off as insulting, but I just find it remarkable how often I see this question + symptoms pop up - even from quite wrench-savvy. Dying clutches are just super obvious to me I guess? High clutch pedal, delayed engagement, slipping in higher gears, etc...

 

while your clutch may be bad, i would put my money on the pos dual mass flywheel being the culprit and not the clutch.
when i pulled the ZF out of my 88 the clutch disc had almost 250,000 miles of very hard miles on it. the clutch looked like it was just put in.
but the flywheel fell out in a pile of pieces.
it was so bad that after 1/2 to 3/4 of an hour of driving, if you hit a hill you would have to downshift sometimes to third gear to get over it.

the upgrade clutch is the luk one piece flywheel setup.

 

No worries there I'll be the first to admit I don't know it all lol

Well the thing is the PO said he replaced the dual mass flywheel shortly before I bought it, although I dont have receipts to prove it. So I dont know why it would be bad. I would think he would've redon the clutch too..

doing some research it looks like I'll need to spend between $500-$850 sound right?

Thanks for your help guys

 

I was also suspecting the dual mass flywheel.

If you pull the tranny and clutch out it should be pretty obvious what's bad if the clutch still looks new or anything.