22re rolls backwards while in 1st gear

[Itsme71190]

as title states, plan on getting a tcase brake but I feel like it shouldn't roll. I do need to do a compression test but I feel like there should be enough resistance through the drive train.
Engine
22re bored .075
LC engineering hyper street turbo pistons
Eagle rods
Lc engineering full perimeter crank scraper kit
Arp rod bolts
Arp head studs
OEM toyota seals and head gasket

Cyinderhead
22re
Stock valves
Valve springs and retainers
Stock rockers and shafts
Engnblder 268c crawler cam
Osk oem toyota timing chain and tensioner

Also looking at replacing the tailgate latch cables. Found these, will they work or is there an alternative?

https://www.amazon.com/gp/aw/d/B07ZBXY71P/ref=psdcmw_15709351_t1_B00FZJDQ7U

 

[Hyde802]

How steep of hill are you on? Does your factory parking brake work?

A compression test would help confirm if the engine is tired. Hows it run otherwise?

 

[SaulG]

Automatic or Manual transmission? I would think manual by description, so have you checked~verified that the engine is turning over as it rolls backwards??
Is it clutch/transmission/t-case problem?

 

[jsabowabo]

Do a compression test. The truck shouldn't roll backwards in first gear as the engine is being forced through the 4-stroke cycle if that's happening. The other option is the engine is being bypassed by something else, like a slipping clutch.