4m40 Transmission "growl" on throttle increase in 4th gear

Mitsubishi Delica L400 production commenced in 1994 -- After much anticipation, the L400 arrived on Canadian Soil in 2009!
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Joined: Tue May 11, 2021 2:04 pm
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Vehicle: S2 L400 Diesel SWB PE8W
Location: Victoria

4m40 Transmission "growl" on throttle increase in 4th gear

Post by rhino604 »

I recently acquired a lovely van (Series 2 L400 Diesel) in excellent condition with ~135,000 km's. Shortly after receipt of the van I noticed an intermittent sound, only during throttle increase when the van already has forward momentum, i.e. if I'm already rolling in 4th gear, and I relax on the throttle, the sound comes for a moment when i give it some throttle again. The sound is usually in the 1.5 to 2k revs range and seems to be louder when the engine/transmission are warmer. I'm also pretty sure it only happens when the transmission is in OD/4th gear. It has a similar sound to a distant semi-truck using engine brakes, if that makes sense!

I'm a marine engineer but a total newbie when it comes to automotive engines, and I haven't yet had time to study any literature on how the power gets transmitted from the engine to the wheels. At first I suspected something related to the engine itself, but I think I've ruled that out since I'm unable to re-create the sound with the van in neutral.

I suspect there's some sort of excess backlash or loose gear somewhere in the connection between the engine and transmission. The transmission fluid appears to be in great shape, even after 5000+ km's of driving with this sound happening, though I haven't opened the drain plug on the bottom, I've simply looked at the fluid on the dipstick itself. This being my first Delica, I don't have a feel to compare whether this one in particular lacks power, but as far as I can tell it works and feels fine.

It's due for it's first servicing at CCA, so I'll be taking it in as soon as I get out of jail (the ship I work on ) in June and let them know my symptoms.

Hoping somebody here has some insight on this noise so I can get a better picture of what might be going on!

Much appreciated Delica fam.

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Joined: Mon Oct 22, 2007 8:42 pm
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Vehicle: 1994 L400 SWB
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Re: 4m40 Transmission "growl" on throttle increase in 4th gear

Post by VanVonVan »

Hiya Rhino,

Do you have any clunks when shifting into drive from park. A u-joint that is going can give some interesting vibrations and "road noise" at certain RPMs. I have change my rear one a few times, that is at the rear diff connecting to the driveshaft. A crawl underneath to give it a wiggle can tell if its bad. ie if you can wiggle it around its bad.

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Vehicle: 1999 L400 Chamonix Gen2
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Location: Vancouver

Re: 4m40 Transmission "growl" on throttle increase in 4th gear

Post by poochike »

Could be a U joint. Get under the van and try and rock the drive shaft. If there's play left and right, you've found the culprit.
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