I have searched. Found one thread with a similar issue, but the solution was not posted.

Hey guys, this recently started happening. About 600 miles ago I had my transfercase replaced (TRE Stage Three) , then shortly after had my transmission worked on by a different shop (buddy shot a dowel pin out of first and second select fork...). The shop that did the work on the transmision WAS NOT A EVO SPECIFIC SHOP, and in fact just specialized in transmissions (tranny is great!).

450 miles later (two days ago), and I am in Fifth gear doing 70 mph at 3k (5 Speed). Acceleration is smooth up to apprx. 3000rmp, then quick (0.5 sec) jump to 3500 to 4000 rpms, with speed increase, back down to 3500rpm and continues to accelerate normally. If I keep rpms above 5k throughout shifting, no problem, just grab and go.

So I figure, "ok...clutch needs bled from install ect." I do this (correctly I've done it many times, I know of the tricky reservoir), road test and everything is great!

Then it happens again. I adjust the clutch this time and bleed it and it goes away... Then comes back in fourth gear, and SOMETIMES fifth at random.

So this morning I bleed the clutch and even push in the slave cylinder to bleed as much air as i physically can. And guess what it goes away...until tonight.

So to sum it up,the problem is intermittent, varies, and is hard to replicate over and over again. I have put on over 200 miles since the start of the problem, and nothing has changed.

I do know that I have throttle body shaft seal leaks, and my intercooler coupler that connects to the throttle body blows off frequently enough to be very annoying (stock, I have tried everything, I'm going to get a new coupler...anywho).

Could this be a boost leak? Or does it sound like clutch. I've never experienced a clutch death like this on any of my previous vehicles. I am stumped, and don't want to shell out dollars for a clutch and install, just to find that the issue is nothing more than a POS coupler of TB shaft seals...

 

Sounds like it could be the start of the clutch slipping. How many miles do you have?

 

The clutch has around 20k on it. Stock clutch.

 

Have you done a lot of launching? I had 60k before my stock clutch started slipping.

 

Yeah I think you are starting to experience some clutch slip. How much power are you making? 20k is around the norm for the stock clutch with spirited driving...haha I'm surprised you didn't upgrade that when you did all the other work to the tranny...would have saved you some money

 

I'm not sure I was making 300 wheel on a mustang before the cams, not sure now(road tune).

I was planning to but when I asked the shop who did the transmission work how the clutch looked they said great...so I trusted them. between the transfercase and install and transmission work I was out around 5 grand. I made a bad decision I guess, but the shop that did the transmission work had GREAT labor rates (I paid 700 dollars with parts included for the transmission) and did a good job. I will have them do a clutch next week I guess.

I was hoping that this issue was something else; bad boost leak or something...maybe even poor instalation, but I guess I'm not that lucky.

 

Hey did you ever figure out what was wrong with your car? I'm having the same problem. Every time I accelerate at a fast rate, there's a delay at around 3000 rpms and then it pulls really hard. I've found a couple of threads where people have had the same problem, but no one has ever posted what the problem ended up being. I really don't want to bring it to the dealer because they are going to charge me a minimum of 200$ as usual.
Thanks

 

Odds are you can't get it to repeat because of the amount heat affecting the amount if friction in the clutch discs.