98 Grand Cherokee Transmission problem: At hwy speed transmission surges or shifts down RPM'S jump 200 to 300 RPM. Only does it when Transmission is fully warmed up.

old 1995
we need vastly more symptoms then that,sorry
if the engine surges, that is first. (surges in 1 gear)
but if a transmission down shifts that is normal, rpm rises
(after all its a lower gear) (higher numeric ratio)
find any machanic in town
ask him test drive it.!
10 min.later he wilt tell you
its trans issues.
or its engine, super easy this is driving.

seems you can not, and learning is 1hour in car class..or 10x that lacking facts of drive train functions.


stop guessing. why spend cash on a useless sensor now.
spend cash on $1 shop diagnosis and WIN.
i promise !

or get it scanned.
and post all those DTC errors. P0700? and more.

Any codes?

P0740-TORQUE CONVERTER CLUTCH CONTROL CIRCUIT...

POSSIBLE CAUSES:

RELATED DTC P0750 PRESENT
INTERMITTENT WIRING AND/or CONNECTORS
INCORRECT FLUID LEVEL
INTERNAL TRANSMISSION PROBLEM - TCC OUT OF RANGE
L/R SOLENOID INOPERATIVE

Further diagnostic with a good scan tool will help, could be all you need is a new solenoid or some electrical repairs. Hope this helps.

Cruising rpm even after the OD has engaged has a lot to do with the differential gear ratio and tire size.
There will always be a variation between different vehichles due to that alone.
To see if the OD is working, at about 50mph, lightly touch the brake pedal. If the rpms increase for a moment then the OD was engaged. (touching the pedal momentarily disengages it...good thing to know when hill climbing!

It could be your transmission trying to find the right gear it will jump around on diffrent road surfaces and going up hills/down hills. It is usaully noticable on cruise because it is at a constant speed and your thinking why would it need to shift. Sometimes it doesnt even really shift the gear its so inbetween it just jumps back really fast.

Try changing the transmission fluid and transmission fluid filter. It is a fairly easy but kind of messy job. Just buy the new fluid and filter, Grab your metric socket set and go at it. NEVER WORK UNDERNEATH A HOT VEHICLE. You have to pull the transmission pan to do this job. When you break the gasket seal several quarts (liters) of transmission fluid will cascade down on you. Be ready for it. Don't forget that when it stops draining there is still a lot of fluid left in the pan. When you finish cleaning up the fluid clean the gunk out of the pan. Install the new filter and reinstall the pan with a new gasket. Do not over torque the pan or filter bolts. If you strip them out or break them off you will need professional help to repair it. Refill the transmission with fluid. It should take six or seven liters.

I'd begin by having the trans fluid changed and making sure there isn't an excessive amount of debris in the pan (there is always some but should not be obviously a lot) You may have a slight varnish buildup inside that becomes less sticky as the internal temp rises.

You sure its the transmission? Wheezing sound is usually the catylitic converter becoming plugged. Also...at 3-5K rpm you are not idling, you are reving the engine...(in that case, trans may be slipping or flairing between shifts, unless the unit is staying in one gear and just delaying shift till you reach that rpm. actual shift point should be close to 2,000rpm) I'd check the cat first.

Check the adjustment on the brake switch. If the brake switch is not seated properly it will engage when hitting bumps and tell the tranny to come out of overdrive.

I would look into replacing the VSS which is the vehicle speed sensor, it is the input that tells the transmission when to go into overdrive and the torque converter to lock up, also make sure the connector is clean and tight to the sensor, this part is located on the side of the trans where the speedo cable would go.