Truck jumping in first and second gear once clutch is let out fully when accelarating

we dont know what was in that kit.
are you in neutral"????????????
does it grind, foot on clutch taking up slack or only fully depressed.
or both.

new throw out bearing
new center of flywheel bearing,? pinion shaft end to fly?
the front bearing on the tranny can be bad
and all CLUTCH techs,no to check that TOO.
does car have hydraulic clutch actuator,MC and slave or is it cables.
there are 3 bearings here

• T.O. (loves to fail , it does)for sure drivers that rid the clutch.
• fly center bearing or bush.
• and front main shaft of tranny (pinion gear front bearing)

all can fail.
or is this grinding going in to 1st or reverse gear, NOT TOLD !

fist gears work , but if you cannot get it into first gear with out grating ( normally reverse will be at fault also) then it is not first gear but a clutch activation problem
if the gear is very noisy , it will be a clutch input shaft bearing or a problem in the bush/ bearing in the end of the crankshaft
if the bearing is faulty then 4th gear will keep jumping out of engagement
so check for air in a hydraulic system or a cable in a cable clutch

Sounds like something with pedal to throw- out bearing. Go to a transmission shop they'll check it for free in most cases!

The throw out bearing will be on the outside of the clutch assemble. What it does is push against the fingers in the center of the pressure plate.

from the description , the noise is a failing throw out bearing
the gear scratching is the fact that the clutch is not fully disengaging and there is still excessive torque in the input shaft for the syncro rings to work properly
fit a new clutch kit ( including new throwout bearing) before you have to rebuild the transmissionas well

4R100 or 4R70W?

Geartrain
Power is transmitted from the torque converter to the geartrain components through the input shaft and forward clutch cylinder.

• By holding or driving certain members of the gearset, four forward ratios and one reverse ratio are obtained and transmitted to the output shaft. The ratios are as follows:

GEAR RATIO 1ST 2.71 to 1 2ND 1.54 to 1 3RD 1.00 to 1 4TH 0.71 to 1 REVERSE 2.18 to 1
Input Shaft
The input shaft is supported by two bushings in the stator support. End positioning of the input shaft is controlled by the splines in the converter turbine and the overdrive planet assembly.
Output Shaft
The output shaft is supported by two bushings in the case and by the slip-yoke and bushing in the extension housing. End positioning is controlled by the parking pawl gear and snap ring or shoulder and by the reverse ring gear hub and snap ring.
Overdrive System
The overdrive planetary system consists of the overdrive planet assembly, overdrive sun gear, overdrive ring gear, coast clutch cylinder, overdrive one-way clutch assembly and the center shaft, as shown in the following illustration. The overdrive planet assembly is splined to the input shaft. The overdrive sun gear is centered by a bushing on the input shaft and held in place laterally by needle bearings on the reactor support and the overdrive planet assembly. The overdrive sun gear is splined to the coast clutch cylinder, which in turn is splined to the overdrive one-way clutch inner race.
The outer race of the one-way clutch is splined to the overdrive ring gear, which is splined to the center shaft. The center shaft is centered by the forward planetary assembly and is laterally held by needle bearings on the center support and the overdrive planet assembly. The center shaft is splined into the forward clutch cylinder.
Two friction clutches are assembled in the overdrive planet assembly. The coast clutch is splined between the coast clutch cylinder and the overdrive ring gear. The coast clutch is activated to perform engine braking in MANUAL 1, MANUAL 2 and third gear with the transmission control switch engaged.
The overdrive clutch is splined between the case and the coast clutch cylinder. The overdrive clutch holds the coast clutch cylinder and, in turn, the overdrive sun gear, to permit the planet assembly to overdrive the ring gear.
--------------------------------------------------------------------------------------------
Forward Drive System
The forward drive system consists of the forward clutch cylinder, intermediate brake drum, intermediate one-way clutch, input shell, forward ring gear, forward ring gear hub, forward/reverse sun gear and the forward planetary carrier and forward planetary gears.
The forward clutch cylinder is splined on the center shaft. The forward ring gear is piloted on the forward ring gear hub. Thrust bearings on the forward planet assembly and forward clutch cylinder hold the forward ring gear hub in place.
The intermediate brake drum is radially supported by bushings on the center support and is laterally controlled by thrust washers on the forward clutch cylinder and center support. The intermediate brake drum has the inner race of the intermediate one-way clutch press-fitted on its pilot. The intermediate one-way clutch's outer race is splined to the intermediate friction clutch, which is splined to the case. The intermediate brake drum has lugs that are slotted into the input shell to form a mechanical connection. The input shell is splined into the forward/reverse sun gear. The forward/reverse sun gear is common to two planetary gearsets. The forward planet is splined to the output shaft and is laterally positioned by needle bearings on the sun gear and on the forward clutch cylinder, as shown in the following illustration.
Two friction clutch assemblies, the direct clutch and the forward clutch, are shown with the forward planetary assembly. The direct clutch assembly splines the forward clutch cylinder to the intermediate brake drum. The forward clutch assembly splines the forward clutch cylinder to the forward ring gear. The forward clutch is activated during all forward gears. While in third or fourth gear, both the direct and forward clutches are applied to hold the forward planetary assembly and enable it to act as a solid shaft.
In second gear, the intermediate clutch assembly holds the forward/reverse sun gears. It is applied, along with the intermediate one-way clutch, to hold the intermediate brake drum, input shell and forward/reverse sun gear. In higher gears, the one-way clutch overruns.
----------------------------------
Low and Reverse Drive System
The reverse planetary assembly consists of the reverse planetary carrier, reverse planet gears, the reverse ring gear, the reverse ring gear hub, the reverse clutch hub and the low-reverse one-way clutch assembly.
The reverse ring gear hub is splined to the output shaft and to the reverse ring gear. The reverse ring gear hub is laterally held by a needle bearing on the inner race of the low-reverse one-way clutch and a snap ring on the output shaft. The reverse planet assembly is splined to the low-reverse clutch hub. The low-reverse clutch hub is connected by the reverse clutch to the case. The inner race of the one-way clutch is bolted to the case.
The reverse clutch assembly is activated in REVERSE gear and in MANUAL 1. The reverse clutch bypasses the reverse one-way clutch during coast and MANUAL 1. The reverse clutch holds the reverse planet assembly in REVERSE gear to enable the sun gear to drive the reverse ring gear in the opposite direction.
-------------
Apply Components
The following information describes the operation of the three 4R100 one-way clutches.
One-Way Clutch—Overdrive
The overdrive one-way clutch, shown in the following illustration, transmits engine torque from the overdrive sun gear to the overdrive ring gear in first, second and third gear range. The overdrive one-way clutch transmits power when the sprags are engaged between the inner and outer races. The inner race is splined to the coast clutch cylinder, which in turn is splined to the overdrive sun gear. The outer race is splined to the overdrive ring gear.
The overdrive one-way clutch engages whenever the overdrive planetary system attempts to drive the overdrive sun gear clockwise when the overdrive ring gear has a counterclockwise torque from the vehicle. When torqued counterclockwise, the overdrive one-way clutch engages and acts as a wedge to lock the sun gear and the ring gear together. During coast, the overdrive one-way clutch enables the ring gear to overrun or spin at a faster rate than the sun gear.
The overdrive one-way clutch overruns when in overdrive (fourth gear). In overdrive, the coast clutch cylinder is held by the overdrive one-way clutch, which in turn holds the overdrive sun gear. This causes the overdrive planet assembly to walk around the sun gear and overdrive the overdrive ring gear. The inner race of the overdrive one-way clutch is thus held stationary while the outer race is allowed to overrun clockwise.
--------------------------------------------

Probably your synchros in the transmission, if so it's cheaper to replace the tranny with a known good/tested junkyard trans.

If it was your release bearing on your clutch you would hear a ringing noise when you push the clutch in to release it.

If the car is in overall good shape you might consider changing the trans and installing a new clutch kit, it will come with the bearings, etc. Be prepared to lose a gear completely and you'll have to skip that gear during your shifting order to get up to speed.

you have 20k miles after the clutch has been changed, now are you used to drving clutch, secondly is it hydraulic or cable controled clutc?

if you are used to drving clutch sys probable cause is defective pressure plate or the throwout bearing is not fully releasing in other words the clutch is partialy applied all the time because of the re;ease bearing not fully releasing!!

Sounds like its not sticking to the flywheel instantly but skippng a little bit and the squeek could be the clutch plate springs groaning.If the clutch and flywheel have been used hard it could have a heat glaze on it that resists grip Probably need to get flywheel machined when you eventualy change the clutch.

it maybe can be clutch plate also clutch bearing.
It can be also in side the gearbox front main shaft when the bearing is worn out it makes noise.