7AT rev slip when shifting 4 to 5

DarkJak

My 7AT revs slip up about 500 rpm when shifting from 4th to 5th under heavier load.
So if I were upshifting from 4th at 4000 RPM, it would surge up a bit to 4500ish rpm before dropping down and locking into 5th

Has anyone else experienced this or know what to beef up? Upgraded valvebody? I'm worried about wear and tear this would cause.

Background:
My local track has a straight where I'm topping out 4th right now, right before braking, and I'm thinking of switching from 275/40R18 to 275/35R18 due to better availability of the more competitive tire compounds. I think that would force me to shift to 5th if I didn't want to bounce off the rev limiter at that point. It's also concerning when it happens around town.

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Ghostvette

This is purely a guess on my part, but usually when a trans start doing that, it means that the clutch packs inside the trans are starting to slip due to wear. What kind of service have you done on the trans? Has it had fluid changed on a regular basis? Not to be negative, but it might be time to pull the trans for a rebuild before it craps itself somewhere inconvenient.

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SouthArk370Z

First thing I'd try is replacing the trans fluid. Not that difficult to DIY, from what I've read.

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DarkJak

I just had my second service last week. The car is now at 39,000 miles and first service was maybe at 20k. It sees pretty hard track use though, so I wouldn't be surprised if you are correct.

Anyone here with knowledge on the Exedy clutch packs?
https://www.z1motorsports.com/transm...at-p-9602.html

The one review on Z1 is very positive.

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@stupidtoycars | My track vids
09 7AT|MCS 2WNR|Topgunz Rotrex|Ecutek (Eugene)|Maxxis RC1|Titan-7 TS-5|OSG LSD|Rear Mount Derale Oil Cooler (WIP)+25 Trans Cooler|Fismo|G-LOC R12/R10|Zeta III L|NLR Wing and Splitter|CJM Pan and Fuel Hat|Radium Surge Tank|AP Racing CP9668