When I accelerate rpm's go to 3500 at 45mph should be around 1500 and keep increasing more as I accelerate but rpm is normal when idling. What's happening?

Sounds normal to me,the rpm's should increase as your accelerating.

Welcome!
What vehicle do you have, year, motor, transmission, etc...
You can add this info to your signature and it will provide others with helpful information with any future postings, questions, etc...!

_________________
Supporting Vendor and Moderator of LOST
05 Jeep Liberty CRD Limited
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
IronrockArms/wwdieselMount
98 Dodge Cummins 24 Valve

The too fast rpm's are on a 2003 Liberty Renegade with 3.7 liter 6 cyl.

It's also an auto trans with high low 4wd but so far it's only doing it in 2wd. Thanks

is it up to operating temp when it does this?

_________________
03 Renegade (Black)
177k miles 3.7L gas - 45RFE
Command Trac / 4.10s
Lift: ft. 790+ rr. JBA4+
The last of the TrailReady Front&Rear Bumpers and TR Rock Rails
Jarhead Offroad light covers
31x10.5R15 RedLetter Grabbers on Blackrock Dunes
L.O.S.T #KD098632

Engine rpm is a function of speed and the gear you are in. Under "normal" acceleration, at least on the CRD with automatic, the rpms will rarely go above 2,500 unless you have manually set the gear selector to 1 or 2 instead of D. However, under hard acceleration your rpms could easily exceed 3,000 and increase until the transmission "up" shifts again unless up shifting is overridden.

Questions:
1. do the rpms drop back to normal once highway speed, say 65, has been reached?
2. what is the rpm at 65?
3. in fact what are the rpms at the various shift points, you should be able to feel the shifts?
4. what's the vehicle mileage and when was the transmission last serviced?
5. have you only used ATF+4 in the transmission and what's the fluid level?
6. does it do this all the time or only on cold starts?

_________________
Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs