Rebuilt auto tranny lurches forward in cold start-ups

[shorepig]

I have a new (rebuilt) auto tranny, torque convertor, diff, and LSD in my 85 westy mated to a 2.3 GW motor. The motor has 100,000 km on it but the rest was installed recently. Also had new drive shafts and cv's installed recently.

PROBLEM:

If the van is cold when started it lurches forward when the engine starts. Not much, but there is a noticable forward motion of a few inches. This only happens on occassion (about 1 in every ten start ups). It has never done this when the van has started when it was warm.

As well, when the van is decellerating and slowing down gradually (imagine coasting to a stop) the downshifts seem a bit harsh (not a smooth shift but rather harsh). When accellerating slowly, the van also has a rough shift when shifting into a higher gear. These shifting issues are intermittent and only occur on slow shifts or when the van is accellerating or decellerating gently. Also, if I tap the gas pedal abruptly there is a definite clunk sound/feeling. BTW engine mounts were replaced recently.

Westfalia gurus, what could be causing this? Is something out of adjustment? Someone else mentioned an issue referred to as "drain back issue" but didn't elaborate. Any insight would be great! cheers!
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85 Westy
92 Mitsubishi Mighty Max 4x4 V6
74 Honda CB500T cafe racer
2013 ktm 690r
Sector nine pintail

[MarkWard]

Hello, are you saying that when you start the van, it lurches forward in park or when you select drive?
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☮️

[shorepig]

MarkWard,

It lurches forward when I start the van in park.
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85 Westy
92 Mitsubishi Mighty Max 4x4 V6
74 Honda CB500T cafe racer
2013 ktm 690r
Sector nine pintail

[Terry Kay]

If this is do, there is something amiss with the park pawl, along with some more items from your description.

Better get it repaired pretty quick.
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T.K.

[shorepig]

Thanks TK

Another thing I've noticed but figured wasn't an issue is shifting between gears is more difficult. It takes more arm strength to shift the selector. Bit of a clunk too when shifting between park, drive, and reverse. This clunking is typical though correct?
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85 Westy
92 Mitsubishi Mighty Max 4x4 V6
74 Honda CB500T cafe racer
2013 ktm 690r
Sector nine pintail

[pablum]

Yeah the pawl or the dentitions it falls into. Have you been throwing it into park while the van is still moving? Or maybe you did what I tried and ran through the gears while the axles were removed with the motor running? Don't put it back in park if you try that.
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The wise man learns from history, the fool from experience.
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I see [a cat] in the street and i aim for the pest with my car. -- bluebus86

[Terry Kay]

Get it back to the trans shop asap.

Let them figure it out.
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T.K.

[shorepig]

Pablum,

No. I stop before putting the van in park someone else did the install so I'm not sure if they ran through the gears without the axles installed.
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85 Westy
92 Mitsubishi Mighty Max 4x4 V6
74 Honda CB500T cafe racer
2013 ktm 690r
Sector nine pintail

[AtlasShrugged]

[AtlasShrugged]

I should add..if your idle speed is too high..the transmission will behave the same way too. Idle speed should be less the 1000 rpms

[Terry Kay]

I have been thinking the same on this phenomenon.

What actually is a lurch?

If the idle is cranked up too high, I would be more prone to describe it as a "Bang"
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T.K.

[amwaj]

he said it lurches forward when in park

could that be idle speed?
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the best way to make a small fortune in life, is to start with a big one, and become afflicted with Vanagon-itis

[Terry Kay]

As mentioned the idle should be under 1000 rpm.

850-900 would be good.

What is your van idling at?
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T.K.