Hard to reach above 6k RPM

[mercedesx7]

Hi guys,

my ride is '91 Auto with 70k miles.. i wonder, after i have warmed up the car for 20 minutes and a drive of 20 miles, it is still hard for the rpm to reach above 6k..

only if i keep driving by changing the gears manually (from D to 1, 2 then 3) with rev limits at 6k rpm, then after 20 miles, i'll be able to reach 7200 rpm range..

Oil pressure seems to be ok.. temperature seems to be ok as well..

Is this normal?

if not, what are the things i need to check/do?

 

[Briank]

Try installing a new thermostat.

 

[IsR]

Hi guys,

my ride is '91 Auto with 70k miles.. i wonder, after i have warmed up the car for 20 minutes and a drive of 20 miles, it is still hard for the rpm to reach above 6k..

only if i keep driving by changing the gears manually (from D to 1, 2 then 3) with rev limits at 6k rpm, then after 20 miles, i'll be able to reach 7200 rpm range..

Oil pressure seems to be ok.. temperature seems to be ok as well..

Is this normal?

if not, what are the things i need to check/do?

Not normal.
Have you tried what BrianK suggested?