Hard Shifting When Hot

[malibujason79]

I have a Muncie transmission in my car and use a hydraulic throwout bearing with an after-market f-body clutch master cylinder. When the car is cold it shifts fine through all of the gears, once the car is hot, it is hard to get into any gear at a stop. If I'm coming up to a stop sign and put it into 2nd and then 1st while I'm still rolling it goes into gear fine, if I'm at a dead stop and hot, I have trouble getting it into gear. Thoughts or suggestions as to what is causing this issue and how to resolve it

[Timbers68]

I’ll start here, what fluid are you using? Only real choice is 90wt. Synthetics don’t work in a Muncie.