Auto gear box for a 1993 300 GEL AUTO estate

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Les Constant
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Hi  I am a newbie to the G Wagon world and had the g wagon fever so just jumped straight in, the overall condition seems fine however my issue is with the auto gearbox it changes ok but when accelerating each gear change is made with a thump not at all smooth please advise if this usual and what do you suggest on what action should be considered   many thanks from Les

Arnie
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Re: Auto gear box for a 1993 300 GEL AUTO estate

The gear changes should be smooth.

The quality of shift (what you are experiencing) is determined by a modulator valve on the side of the gearbox. These were upgraded after 1993,  so you may need to replace yours at some stage for the best improvement. The cost is about £70. However, the valve is operated through a vacuum line, which may have become disconnected causing the hard shifts.

Often, the required oil changes on auto-boxes are neglected, so the oil and filter should also be attended to, as the first thing you do. Initially change the transmission fluid with regular Dexron-II or III type fluid and once the issues are resolved you can do a further drain and refill with a synthetic transmission fluid likes Fuchs 5000 SL. To fully drain the system you need to also remove the torque-converter drain plug (see manual).

Take the dip-stick out for the transmission fluid and if the oil on it looks brown or has a burnt smell, then change the fluid ASAP. Check also that the fluid level is correct. this should be measured with the engine running and the transmission in P (and handbrake on).

Generally, if the gearbox shifts to reverse and forward gears quickly without delay, upon moving the lever, they gearbox itself is probably OK.

 

Read this thread and check the YouTube links:

http://www.gwoa.co.uk/content/auto-transmission-oil-filter-change

 

 

gooch
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Re: Auto gear box for a 1993 300 GEL AUTO estate

Hiya,

Action it immediately, can get worse from experience. It should have very smooth responses all the way. check auto box filter is not clogged. Renew fluid.

if that fails, there's a chap here in my town hoddesdon-herts that basically releases or increases the pressure in the hydraulic system. Which usually works every time. It could be there's too much in the system making it not switch gear at the right time.

Owned many 463 g300, the boxes are pretty solid though.

you may find someone closer to you who understands 'auto transmissions' well, it's simple technology on the 4matics ! 

Regards

Les Constant
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Re: Auto gear box for a 1993 300 GEL AUTO estate

Thanks Arnie,  That's  grate advise, I am of to my garage shortly to check out all the points i will respond  thanks again   Cheers from Les 

Les Constant
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Re: Auto gear box for a 1993 300 GEL AUTO estate

Thanks G   i will check out all what you suggest   Thank you from Les 

Arnie
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Re: Auto gear box for a 1993 300 GEL AUTO estate

gooch wrote:

.....there's a chap here in my town hoddesdon-herts that basically releases or increases the pressure in the hydraulic system. Which usually works every time....

 

That's the modulator unit (valve)  on the side of the box. It's vacuum operated and is also adjustable by removing its cap and turning one way or the other to make the gear-change softer or harder.

However, don't make it too soft, as it will wear the clutch packs more quickly. The problem may be that the modulator valve has failed or that the vacuum signal from the engine is disconnected or loose.

The modulator valve is not expensive and quick to replace. But first change the transmission oil and filter. Also, if your car is fitted with A/C, the A/C condenser (front radiator) is very close to the front of the main radiator and if your car has ever done any off-roading of fording, the proximity of the two radiators tends to accumulate a lot of mud and dirt between them.This cannot easily be seen, nor cleaned out, and has the effect of causing the system to run hotter, including the auto-transmission fluid-cooler, which is part of the main radiator,  and the fluid eventually degrades and starts to clog up infernal valves, which can also lead to hard shifting. So,

  1. check the radiator(s) are clean and clear of dirt,
  2. change the transmission fluid and filter.
  3. check the vacuum line is connected to the modulator, without leaks.
  4. replace modulator with upgraded version if necessary.

 

cox.adrian
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Re: Auto gear box for a 1993 300 GEL AUTO estate

  as gooch says oil filter first  

    for S EAST  sussex auto transmissions  station road ind estate hailsham

​    very good reputation  

https://www.google.co.th/maps/place/Auto+Gearbox+Specialists/@50.8555669,0.2589752,17z/data=!4m2!3m1!1s0x0000000000000000:0xa839c4b44df0c449?hl=en​

bigblock
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Re: Auto gear box for a 1993 300 GEL AUTO estate

Lots of detailed advice from Arnie including a few things I didn't know.

Always good to learn something new, thanks.