Hi

Been away for a while (3 years in East Africa). Exported my vehicle out there in 2004, problem is I have recently been having some problems with my gear box: basicaly all is OK around town however when I go on a long run at 50+ mph the gear box heats up drastically and I loose 1st, 3rd and 5th gears. However if I continue at speeds lower (say max 40 in 4th gear) evenyually the gears cool down and I can get it into 5th again. The problem then comes when stopping - I have to leave it long enough to cool so that I can get it into 1st to pull off. 2nd is a definate no-no when fully loaded (around 3000kg).

Anyone have any ideas as to what is going wrong and how I can sort it?

Thanks

 

Have you checked the oil? Does it feel like the clutch wont let it go into gear?

 

The problem only occured after dropping the box and replacing the third gear thingy (it was kicking out of 1st and 3rd). That happened in Zim, I then drove about 1000km to Lusaka (at about 80kmh) in Zambia where I thought that might be the problem and changed both 4wd transmission and gear oil.

After a short test drive it seemed OK but after about 150km back on the road I experienced the same problem. Nursed it 4000km to Nairobi where I had the gearbox dropped and checked - my mechanic could see no problems and all tolerances seemed OK so we reassembled. Around Nairobi everything worked well, however after 6 months there we drove down to South Africa (about 6000km) again the problem occured and I had to nurse it home at 80kmh.

Now I'm going back to Africa to pick up the vehicle and want to get it sorted this time so any hints as to what I should look out for would be appreciated.

 

When the engine is cold, the clutch etc works fine. Gear changes are smooth and clean - this problem only occurs after a couple of hours of continuous driving at 80-100kmh.

 

try differnt oil and when it wont let you go in try leting the clutch out just a little bit when your trying to get into gear and see if it goes in or just drive with out the clutch if need be

 

I'll try that. however what concerns me is the great amount of heat generated in the gear box - I've got a mul-t-lock bolted to the side of the box and this gets hot, hot, hot! Is this a clue?

 

Hmmm....don't know what a mul-t-lock is.

What kind of gear oil are you running in the transmission?

 

mul-t-lok is a brand of padlock; for car security a plate is bolted to the gear box and that extends up into the cab. The low/high 2wd/4wd leaver (or the gear stick) can then be locked in neutral using a special U bolt and lock.

SAE 75W-90 transmission oil

 

Put some known good 75w90 api GL-4 oil in it. I'll bet that they used whatever they had, which is probably OK for beating around in the bush, But problems arise under sustained loads.

I will say though that being 1st, 3rd, and 5th is curious since those are the gears that engage in the rearward direction in the gearbox. So I guess it's possible that a collar is getting hot and slipping on the mainshaft and allowing things to get out of position.

But try the oil first

 

Someone on another forum suggested:

Castrol MTF 1067 PLUS - fully synthetic SAE 75W/85W manual transmission fluid.

Just have to see if I can get some in SA before we pick up the truck in Zim.

 

To be honest - I do not really understand the workings of the gearbox. Can someone point me at gearboxes 101?

 

Here is some info, Manual Transmissions Basics


I'm sure you can find more with a more diligent websearch