95 Riv Overdrive

I took a trip in my 95 Super Charged Riv from L.A. to Central Cal. I was taking my son and his cargo to college. His stuff filled the trunk and the back seat. My wife rode in the passenger side.

I would say there was 200+ pounds of cargo.. my wife and I together added 325 more pounds. Didn't seem like a big deal to me.

The self-leveling suspension worked perfectly with no sagging or bottoming out.

However, once we got going I noticed it never shifted in overdrive (never). When I got up around 75mph the engine was 3000rpm. Consequently, I got about 17mpg.
.

Once we unloaded on the way back I got 27mpg. at 70mph the engine was at 1800-2000rpm.

I understand the system detected the extra weight and prevented OD, but on open flat highway OD should have kicked in. OD should only be prevented during acceleration, inclines etc. I wondered is there any malfunction (trans fluid full, no warning lights).

Advise.. anyone?

You are correct, it should have dropped into OD under light throttle and basic cruise. Was your wife holding the shifter in D?

The 4T60 transmission tends to run hot. Particularly when there is extra load on it. Once it get's hot enough it will not hold overdrive. If you have access to a scanner try scanning to see your trans temperatures. Usually anything above 210-220 degrees the trans will not hold overdrive.

Buickman104 wrote:

The 4T60 transmission tends to run hot. Particularly when there is extra load on it. Once it get's hot enough it will not hold overdrive. If you have access to a scanner try scanning to see your trans temperatures. Usually anything above 210-220 degrees the trans will not hold overdrive.

Thanks......

I have this problem with my 95 as well. Is there anyway to solve it?

As stated above, find out your T-fluid temp. Try adding a cooler?

lost overdrive pulling a hill change fluid or, when it cooles down will it come back?

...also check if your front brakes are dragging. Raybestos makes little springs to discourage brake pad drag (look under brake pads on RockAuto.com for them). That extra drag can conceivably keep you our of OD if you're loaded enough.

Need to determine what you mean exactly by "lost overdrive". There are two components needed for OD to work properly: 4 gear and torque converter clutch lock-up. Did you lose 4th gear, or did the TCC stop working? Usually TCC isnt engaged anyhow on a hill, so im guessing you lost the gear. If you noticed a big jump in RPM, it was probably stuck in 3rd. This could be mechanical, or it could be the PCM thinks the trans is getting hot, so goes into limp mode. TCC lock-up failure is less obvious, a smaller bump in RPM. However, this situation can lead to overheating and eventual torque converter or transmission failure. Often you will see a code when TCC doesn't lock-up. If not, I don't think most drivers would notice unless you look at the tach.

When this happened, how fast were you going? How long of a trip was it? Any firm shifting? Ever happen before? Does OD come back the next time you drive the car? Any SES lamp?