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Doug
Doug, ASE Certified Technician
Category: Transmissions
Satisfied Customers: 8569
Experience:  ASE Certified Diagnostic Technician
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Mitsubishi Montero Limited: hey Doug, got a 2002 Montero Limited.

Customer Question

hey Doug, got a 2002 Montero Limited. Transmission got stuck in 3rd the other day. Can't reproduce it, and my son was driving. That said, it has seemed slower to engage over the past months. He put it in manual, and it still wouldn't move out of 3rd. One other issue is a clunking noise when transmission engages, or a quick on/off throttle so there is 'play' in something, either rear end or in the tranny itself. Same clunking can be heard when one engages transmission while the AC is on and the startup idle is above 1300
Submitted: 1 year ago.
Category: Transmissions
Customer: replied 1 year ago.
Once driving the transmission behaves 'normally' apart from any quick on/off of the throttle, which produces the clunking sound ...either in the rear end or...? WHen trans. fluid was replaced, Mitsubishi trans fluid was used. So it would be good to have an idea on why it is slow (2+ sec ish) to engage, possible causes for getting stuck in 3rd, and whether you have heard of that rear clunking sound...and its possible location.
Expert:  Doug replied 1 year ago.
Hi,
The slow engagement, provided the fluid level is correct and good quality, will only be a pressure related issue. The time before engagement is the transmission building fluid pressure to engage the holding elements for the gear.
This can be related to the oil pump, the regulator valve/valve body, or seals inside the transmission bleeding off pressure.
However, it is also possible to have friction materials that are just so worn down they require more clamping force than normal to engage, causing the fluid pressure to need to increase excessively.
The delayed engagement in itself will cause the 3rd gear stick... that is a fail safe move by the transmission and will occur anytime a strange reading is picked up by the sensors (when there is delayed engagement it shows as a ratio fault putting it into fail safe if the delay is more than 1/2-1 second).
Because of this the first thing you need to do is get the vehicle to a transmission shop with line gauges and do a full system pressure test to determine if you are in fact slow to pressurize specific circuits or not. Either way however, if the fluid level is correct and good quality, you are going internal no matter which is the case.
As for the noise that is something that would have to be heard, however given that you are having delayed engagement that will always carry with it some clunk like noises as the engaging of the gear is happening at the wrong time and the slack in the driveline is taken up at incorrect time/speed. This can sometimes be noise in the planetary set but most often it is noise in the drive shaft or rear differential.
I would not consider this an issue until after the actual transmission operation is corrected and you find that the noise persists... it is likely to go away when the transmission operation is restored to normal.