My auto transmission seems to be going in and out of O/D at slow speed . Also when you stop and start to take off it goes to almost 3000 rpm's then makes a clunk sound then takes off

FORGOT TO SCAN THE PCM I SEE.
check all fuses.?
not told
fails hot and cold engine or both
car must be in transmission DRIVE selected? right?
and foot off gas pedal (accelerator)_ rpm goes to 2000 or up to 6000 rpm . and or
so driving foot off the pedal and RPM goes too high
or in drive, I step on the throttle (gas) and RPM shoots way high
and Never leaves 1st gear. that is transmission failures.
in DRIVE.
if rpm also goes that high right foot doing nothing and in park
that is engine idle control's failing.
we can not see you drive or how. so answers can be a tad hard.
in what gear? PRNDL (choices)
right foot doing what?
and what SPEED is too slow 20 or 85mph? or?
does tranny fail to upshift?

2wd right?(1995 is GEN1, T100)
auto trans or manual trans no told and both are told.
we can't guess drivelines blind,so tell it.?
2.7L, 3.0L and 3.4L engine options new.
toss coin land on A/T box. (most common )
the TCM decides all this not you,
the Tcm/Pcm/or TCU are all transmission brains , the PCM does engine too, and tells the TCM speed, and engine loads (hills etc)
rpm based on all that and gear ratio, in the transmission, 1:1 or overdrive. too and the axle ratio and tire size (circumference)
are tires stock, or low rider tiny.???????
5 speed manual or 4speed automatic and 4 engine choices not one told and if an automatic the TCM is turned to all things stated above.
a hard fact that. the RPM drips in OD ,overdrive and TCC lockup
the service manual lists 5 transmissions
A340F, A340H, A440, A442F and A343F units
top 2 are A340e & A340f (USA answers me) 2wd/4wd

A340F (30-40LE) 4speeds + tcc

seen too on
2000-2004 Tundra (4x2)
A = Aisin-Warner Automatic.
340 generation 3. 3L v6 used.
E=electronic shifted (TCM brain
F= 4wd same as E shifted.
3 electrically controlled solenoids for shifting and torque converter(TC) lock up(TCU runs the SHOW)

There is s TV cable here too, that causes upshifts late or early.
super hard top find this, Asian boxes. but here goes.
?1st: 2.80
?2nd: 1.53
?3rd: 1.00 (end to end lockup , look ma' NO gears here !)
?4th: 0.75 (23-spline, 0.705 21-spline
4th gear cam be less on smallest engine.(less rpm drop)
now you learn vast version of transmissions exits.
I read the side of box and it tells me the model there fully, every time.


so are you not getting 4th gear OD or the TC lockup failing
scan the PCM see if there are P07xx errors"? tranny errors. ?

in 3rd gear the RPM is the axle ratio and tire diameter (pi X r squared is circum and distance moved is that)

I can tell you the math below see the online calc. at end here.
and some TC slip. (it slips not locked up)
4 gear is RPM ,= is 0.75 x 3rd gear RPM. and tc slip.
TCC lock up is is less RPM but that depend slip and hills.
that is why I call them slush pumps, TC SLIPS and turns HP in to wasted heat and is why TCC was mandated by the EPA, for more MPG, and less waste.
that is how the pump slips as they say.

why not just see if all gears work (count them with easy right foot on flat earth)
and TCC locks up, in 4th
and scan the PCm for errors.
1,2,3,4+TCC is really like 5th speed, if you noodle that.
4-1/2" gear,(5th) locked.
make sure TV cable not rusted and jammed up and for SURE not jammed in the Pulled out position, rusted, there. and is WOT
wot is wide open throttle and that make the tranny shift way late
or never goes past 3 gear... test it.(or worse 2nd)
I see folks put a new transmission $2500 for the want of $20 cable.
wow. that. The TV cable bad is an on car fix.
P0750 to P0770 are all tcc errors to the box. scan it if gears ever shift wrong. and speed sensors failing or clutch packs slipping in the box,will dtc code out too.

so in 3rd gear the axle 3.4L auto T100 4x4 should have 4.30 gears.
so 1:1 x 4.3 is still 4.3 so 3000 rpm the read prop shaft.spins

at 3000 rpm and axles spin 698 RPM( AND TAD LESS TC SLIPS.)
knowing tire circumstance or diameter. nets speed.
manual trans runs 4.10 axles. (and no slip at all)
if not running stock tires the SPEEDO lies to you.
taller large tires spin slower and VSS lies. to cluster.
called ticket getter
235/75R15 (stock'ish)
Diameter : 28.9"

here is 4.3 axles.
3rd gear, 60mph , axle above 28.9" stock tires
is 3000 RPM
so shift to 4th, be on flat ground and light right foot and not hills]
and TV cable not JAMMED (rusted and locked out)
https://purperformance.com/p-29669-rpm-calculator.html

so 4th OD is, what .75 x 3000 is 2250 RPM (my guess never seen)
TCC locked up ,is less RPM, a bit.

so learn to scan any TCM(PCM) when gears fails.
scan it. now.

The idle air control solenoid is very common to quit working. The only other thing would be a large vacuum leak.

sounds like your transmission is going bad fast. get it checked asap to see if it can still be saved. aamco will take a look at it. if its completely bad, then getting a new transmission might be cheaper than getting the current one fixed so look into that!!

With the little information I was given there is two possible answers,The first is not an easy fix or a cheap one and that is a slipping band in the transmission and the second is the speed sensor on the transmission eighther one would require having it looked at by a transmission shop.

You may want to check the cpu and see if he upgraded it when he did the trans,bully dog makes a tuneable one thats really good.

try to reset the computer if that doesnt work reset the idle speed it may have picked up bad codes

for better help with this go to mpvclub.com there are a great bunch of guys there, with ALOT of expertise.

With normal acceleration the 1st to second shift point should be around 2500-3000 rpm. Most of your shifts under moderate acceleration will take place at this same point or when there a light load on the transmission. Under hard acceleration the RPMs will climp higher due to increased power needs and the computer will shift when less power is needed or the RPMs climb to an unsafe speed say5000-6000rpms (depending on where yours redlines). Also going up a steep hill will raise the RPMs higher and goind down a hill will cause a faster shift at lower RPMs. These can always be altered by an individual owner by adjusting shift points, using performance parts and if you have problems (low tranny fluid/trans issues). Your trans RPMS are fine and will vary depening on how your foot accelerates. The shift pattern should be the same every time you drive slow/medium/fast/, look for changes in those patterns you will also catch a problem early.

one unit that operates ratio changes and is connected to the engine is that vacuum operated actuator on the transmission
it is possible that that unit is failing , vacuum hose is leaking and that will cause ratio changes as the vacuum varies
run the fault codes to check for wiring problems or VSS or TCM problems as well