89 cherokee laredo shifting funny

Hi, I have an 89 cherokee laredo. It has the 4.0 6cyl. with automatic transmission. Heres the problem. With the transmission selector in comfort, it shifts smooth until it shifts from third into fourth and when it does it produces a big jerk. With the transmission selector in power, it shifts ok in all gears except from second to third which isn't as bad as the other let me know something

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Well start by checking the fluid (tranny warm, idling in neutral) and then check the transmission mount, they break and cause hard sometimes violent shifts.

do you think if the bellhousing bolts were not tight it would jerk like this. I haven't checked them yet but I'm going to