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Advice re my 'new' 300GD

fig

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#1
Hi all

As you may have seen from the For Sale forum, I just acquired a 1982 300GD SWB. Overall it's dry and mostly straight, but has been badly abused in recent years.

The most pressing issue is that both the centre and front driveshafts are worn, especially the front. The vibrations make the car pretty much undriveable over 60km/h.

What is the best way to deal this? I've heard it's best to buy new ones from MB ($$$). Others have told me that Drivelines in Spartan know how to do a proper job of building new ones or rebuilding what I have. What are the forum's recommendations?

The brake booster is also non-op. Can these be rebuilt? Is it a G-specific part, or can I use one from another MB?

Once the engine is warm, it doesn't shut down when I turn the key off. I assume this is a faulty fuel cut-off solenoid. Where would I find this on the engine?

When I got the car home on Saturday my first task was to work out why it was not getting full fuel. I found a perished rubber damper on the accelerator linkage as Andrew suggested I would. I made a temporary repair with cardboard and a cable tie, which allowed full throttle. Wow! The car accelerates like a bomb! Better than my W123 300D. This damper looks like a very poor design. Has anyone modified it to make it more robust?

The only other issues on the car, apart from interior aesthetics, are:
Snatchy gearbox (I'll first check the box isn't filled with hypoid oil instead of ATF)
Odometer non-op
Aircon non-op

I'm looking forward to getting the car roadworthy, after which I'll deal with the lesser mechanical issues and aesthetics.
 

Gerhard van Rooyen

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#3
Congrats Fig.

I am sure you will enjoy fixing it!

My 2c regarding props - 3 options as you mentioned. lowest cost would be to rebuild yours with new yokes and "cups" - I have had one successfully rebuilt before without any vibrations.
second option would be new-build. not original and probably not strong enough for another 30 years but will be fresh and vibe-free.
If you would like the G to be 100% original etc. you can buy a new one from MB. if you have time you can search around for imported stock lying around or so.

If I am not mistaken Greg may still have a fairly new one.

All the best.
 

fig

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#4
I spoke to Drivelines and they say they can build me new shafts to same HD spec as original for about R6.7k each.

Does this sound right? Any other suggestions? Anyone have any MB or OE originals lying around?
 

JJVDMZN

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#6
Regading your engine not switching off and the brake booster not working, maybe check that the vacuum pump is working properly, both are relying on vacuum to work.

JJ
 

Rolf Redecker

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#8
Are you sure the vibrations come from inside the axle? Driven it without front and rear prop shafts (alternating).
How are the prop shafts? Alignment of those.
Regards
Rolf
 

fig

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#9
Are you sure the vibrations come from inside the axle? Driven it without front and rear prop shafts (alternating).
How are the prop shafts? Alignment of those.
Regards
Rolf
I'm quite certain the vibrations are from the propshafts. Both centre and front shafts have play in the UJs. Front is especially bad. Rear propshaft has no play.

I initially mistook the noises from the UJs as coming from the axle when I tested the car in 4WD.
 

Antony

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#10
Hi Fig,

Congratulations. It’s been a long time.

I had great speedo refurb service from Reef Industrial in Marshalltown Johannesburg.
(011) 334-1544

They did a complete rebuild of a broken speedo for me in a day for R1500 last year.

Regards
Ant



Sent from my iPhone using Tapatalk
 

Andrew

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#11
Well it still looks good!

Remove the front propshaft, and drive it like that, making sure you engage SA on the transfer case otherwise your speedo wont work and the transfer case will not lube itself properly. I believe it will then be driveable enough for you to make decisions about the shafts more carefully, and get it roadworthy etc. Drivelines in Isando understand G's.

The OEM shafts have crimped joints, ie not re buildable.

The fuel shutoff valve is mounted either on top (plastic and inexpensive) or at the back (pressed metal and pricey) of the injector pump depending which pump you have. Before replacing check the soft joints to the hard vacuum lines for leaks. This includes the vacuum switch that is piggy backed to your ignition switch.

Brake booster agents only or apparently Mercedes 450 SLC. With just a little violence a VW 2.6 caravelle works very well. You need the master also - then if required shout here again regarding what violence.

The snatchy gearbox normally begins with third and it is the syncro's. Dirk knows this gearbox like his hand. I might have a complete spare gearbox.

The odo is typical. Its drive gear is stripped. I think the VDO repair shop in Fishers Hill Germiston are still active.
 
Last edited:

Alan

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#13
Most has been said above. You can easily test the shutoff by just sucking on the vacuum line going to the pump as well. That will eliminate the shutoff valve on the pump itself. Work your way back. If it never was able to shut off my money is on the shutoff valve on the pump. They do fail and I have replaced one before as well, was about R700 - R900 from Bosch diesel electric but MB was cheaper.
 

Heinie

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#14
Enjoy the restoration Fig. That is the deal, one only get to know about the underlining issues once you drive it.
Fun part is getting it to work properly again. It is like a drug - cant get rid of it when first under your skin....
Looking good from the outside tough.
 
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#16
So I removed the front propshaft over the weekend and discovered that the front axle has an 8-bolt flange while the transfer case has a 6-bolt flange. The worn shaft had holes redrilled for the 6-bolt flange and they have been ovalled out, which implies they were loose at some stage. I haven't done a proper inspection of the TC flange to see if it's damaged, but I'm guessing I'll find ovalled holes.

Now that the front propshaft has been removed, the car won't stay in 4x4; it keeps slipping back into 4x2, so I have to wedge the drive shift lever in place. Is this normal or a sign of wear in the TC? At least the car is now driveable, but still a lot of vibration, possibly from the worn centre propshaft, although I'm not feeling it on the drive shift lever.

I'm not sure what to do next. I guess it's time to do some R&R on the crunchy gearbox and the transfer case, and have an 8-bolt flange fitted to the front of the transfer case.

Can anyone recommend someone who can do the work for me? Is Dirk Wentzel working on Gwagens again?
 
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#17
I also checked out the vacuum/braking issues. I discovered that the engine does shut down, so long as the brakes are not applied on shutdown. I guess this confirms that I am getting vacuum and that the leak is in the brake booster, as first suspected.
 

Alan

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#18
The 6 Bolt flange was used on the very early models.
4x4 should remain engaged. You could shift the lever to the middle between the 4x2 and the low range. i.e. when the lever is towards the back you can move it left and right and it is still 4x4 high.
Center shaft you can test by putting TC in Neutral and selecting gears on the GB and release clutch. It will spin up the center shaft and you can feel the vibrations if any on the gearlever or TC lever.
 

Alan

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#20
Old G's had 6 Bolt pattern on flanges. Was then changed to 8 bolt pattern. This seems to be a home fix of sorts. They were not mixed to my knowledge.