Bad torque converter

check the TPS sensor as it could have a bad spot in it. also the trans maybe going in and out of overdrive at that speed.

Shudder could be the lockup torque converter if it is an automatic transmission. Another one would be the drive axles. Check the CV joints and u-joint in the drivetrain. If the shudder comes and goes with load changes, it could be either. However, to tell if it is the torque converter, watch the tachometer when the shudder occurs. If the RPM rises slightly, then drops off as the shudder stops, it is the torque converter. There is an additive for this issue that can be purchased an any parts store, called shudder-ease. Hope this helps you.

The first thing that comes to my mind is "45 MPH"... and let me explain why.....

Your engine you said is running GREAT so a MPH is not going to effect the running of the Car but what happens @ 45 MPH you ask?

Your Torque Converter goes into Lock up.... If the Torque Converter is slipping in and out of lock up, you are going to have an irregular pulsating of the engine playing catch up.

you need to do this, try and drive the vehicle (you did not say what kind of vehicle it is), and drive it without the OVERDRIVE On...

So drive it and see if it is RPM RELATED. If there is no CHUG and you can go all the way to 55-60 without issue, Slow down below 45 and put the OD IN and accellerate and see what happens..

Is the Problem SPEED RELATED? Is it RPM Related?

If it does not happen with it OUT of OD, then what you probably have is a Torque Converter Failing...

I hope this helps

If it does it only at highway speeds...over 40 mph or so....you could have a lock up torque converter issue. (This locks up electrically for overdrive) Dissable the overdrive and see if it will go away. (drive it in 3rd, if you have a 4 speed) (Or tap the brake, this will dissable it also)

Does the trany fluid smell burnt? Might want to have the trany flushed - torque converter too - and replace the filter in the trans. FYI you may know this but it is not recomended that overdrive be enabled when pulling a trailer - especially a heavily loaded one. Does your town have lots of hills - this is an added stain on the trany.

the throttle position sensor may be "noisey" causing computer to think your are accel. that unlocks the torque conveter. try a new one
also make sure the brake lights on coming on and off when driving that will do it to.

I would leave the gear ratio you have in there. If you go to a 4:11:1 ratio you are going to be turning higher rpms which means more air/fuel mixture being burnt. If you go lower say 3:55:1 you will loose your pulling power.

Dear kev4,

The problem seems to be originating from your gearbox. The gear box has two main components that convert the torque of the engine to the tailshaft; the 'torque converter' and the 'bands' within the gearbox. If at higher rpm the car starts to rev higher and slow down then it would suggest that one of these two components are slipping or not functioning correctly.

To fix this problem you will have to take your car to a gearbox specialist who with either reccomend a replacement gearbox, a overhaul of the orriginal gearbox or if you get lucky a new torque converter. Unfortunately this car be a costly opperation but is quite important in reguards to the life of the vehicle.

Reguards luke.

Hi I am Vortash sounds like Torque slip check your fluid levels in the transmission. Rpm will rise if there is weak drive then as the vehicle reaches change speed it will snatch because the rpm is high .. if your levels are ok you may need to get your Torque converter checked out .. hope this helps regards Vortash

When the transmission jumps the extra RPM by 200 or 300 RPM. That's your Torque Converter Clutch lock up disengaging or it's slipping. Pull the transmission dip stick out and check the fluid level and condition of the fluid, look to see that it's not burning. If the fluid is not burning then it's the Torque converter clutch unlocking and the Throttle position Sensor may need to be readjusted, or if the transmission is still running off a TV cable. The TV cable may need to be adjusted and or the transmission filter may be dirty and needs to be changed. Take it to a transmission shop and explain to them what the transmission is doing. I'm not sure if your transmission is an 4L80 or a 4L80E. If it's the 4L80E the PCM and ECM control the lock up to your converter. If the PCM detects a problem with the transmission, it drops the transmission fluid pressure to the converter clutch. If it's a 4L80, it's controlled by the TV cable and vacuum lines to the transmission modulator. Regardless they can look in to this when they change the transmission fluid and filter. Recap: Have the Suburban's ECM scanned for any transmission DTC codes. Service the transmission if the fluid is dark in colour and burnt. Adjust any linkage to the transmission that is an issue to it's performance. Good luck and keep me posted, be glad to help.