So long story short, I upgraded my vortech setup to make more power. Now, when I'm on the dyno getting tuned, we have a 1000 rpm discrepancy and my tuner telling my my trans is probably slipping, also no more HP made but a good amount of TQ.

WTF is going on? I thought trans wasn't supposed to slip until 450hp or so? I'm only making ~370. Now this is on a notoriously low reading mustang dyno, tuner told me I'd be at around 400 on a dynojet but still... I've always taken good care of the trans, changed fluids, monitored temps. I also installed the transgo shift kit which is awesome. Trans only has 60k miles on it, 20k with the shift kit and 10k boosted. I've done a few Auto-X and a track day but I don't really beat the car to death. Everything feels smooth while driving normally and it performs well under load but I have noticed lately that when I start getting on it in first and second gears I hear the engine rev but I just don't feel like I'm moving as fast as I should be.

Just some points to note.

Previous to new mods I was putting down 368hp/281tq @ 7psi in April. Weather was a lot nicer then here in Dallas, TX.

I installed a 2.87 pulley (from 3.12,) a fuel return I put together, and a fluid dampr crank pulley. When I went to get retuned it was a hot day in July, around 100f and I noticed my intake temps were pretty high at 65c. So I know I need to do something about intercooling that air. I'm sure part of the reason it was so hot was because I was now boosting around 10.5 lbs. My new numbers were 366hp/319tq. No idea where all the TQ came from but I was disappointed with the lack of HP gain. Something doesn't seem right to me.

Anyways. Here is my dyno plot with the mysterious missing 1000rpm. Please note, the car was rev'ed out the same in both sessions. The dyno was also calibrated multiple times at 3k rpms so we are attributing that loss to something in the transmission. Hopefully some of the wise experienced folk here could shed some light onto what is going on.

 

looks like its time for 6mt for you too lol, bump for the homey...i am of no assistance

 

In to troll

 

figures..

 

Probably your trans I take it that 1k drop wasn't there when you dynoed N/A before.

Can't you run a SC NA by taking of belts. If you can see if the dip is still there or maybe your belt is slipping from going to the 2.87. GL with whatever the problem hopefully it's not the trans.

 

I'm sure it's the trans.
I had same issue at 360hp but 399tq

 

You did have gains except for the lowend the run was cut short to see your actual HP gains. The red line on top is the 2.87 right?

 

Depending on your yr G a built one is for sale for cheap in the marketplace.

R1 his tq is no where near yours and doesn't hit as hard due to being SC.

Go back to the 3.12 and see what happens.

 

Check your trans fluid. If it has a burnt smell, it means you're burning the clutch plates and they're wearing out.

 

It looks like you just needed to keep going. The run ended early - that's what it looks like. You can try bumping up est torque in your UpRev flash and drain/fill the ATF.

 

Dash is ur tranny still stock? The trans in the market place is already sold. I told him to buy it but he didn't listen. I went 6mt to avoid all the issues

 

Rob go buy that bult transmission!...oh nvm damn that was a good deal

 

After I installed the built longblock with low compression pistons my numbers are 360/360 and trans was still slipping

 

No it's a fully built GTM stage 3 trans and it's held 500 wtq/whp for nearly 30k miles and 4 years. The key is keeping the ATF cool (below 220 F), install the valve body for no-slip shifts, and frequent fluid changes (every 6k ATF drain/fill). It looks like it reaches it's limit around 575 whp above 6k rpms (doesn't slip completely, but power drops off). Below that it is rock solid.

My turbos are likely good for 700+ whp now, so I may end up doing a 6MT swap also. The sad part is I will likely have a slower car! 5AT's seem to be as fast as most 6MTs with 75-100 more whp (on the airstrip )

 

the car was taken to redline on the dyno on both runs. It wouldn't go any farther. So basically, the car said it was doing 6900 rpm but the dyno said it was doing 5900... dyno was calibrated multiple times and same thing happened. Runs were done in 3rd gear.

 

also I should note my trans fluid rarely gets over 190F

 

Doesn't look like he hit the rev limit though... you SURE he ran it all the way out? The stock tach climbs faster than actual RPMs... mine is at least 500rpm higher than my datalogs on pulls. If you have a video of the pull I'll tell you what RPM you're hitting.

 

I remember pretty distinctly him hitting the rev limiter because he was watching the dyno screen as he did the pull. we were both like WTF.

 

you know, I didn't take a video. I was about to except I was embarrassed with the numbers and was pretty sad to hear my trans might be slipping already.

 

slipping shows up as engine speed goes up while tq goes down. I'm not seeing slip here.

Looking more closely at the two overlays it look like it's not picking up your RPM signal correctly -- the new chart is squished to the left (A/F, boost, tq and all). I'll put money that the dyno run is ****ed. HP is simply a function of TQ x RPM and the tq and boost looks legit.