Hilux Ln166: Loose Gbox Bolts, Cant Get Into 5th & Reverse

[lemmyb]

I have a 1999 Toyota Hilux 4x4 (LN166) in which i have just installed a Toyota 3.0D (5L) engine. Previously the car had the 2.8D (3L) engine. I did not change the gearbox. I have driven the vehicle for almost 20 000km without a major problem. I use the vehicle quite often on dirt/muddy roads, though most of the time i use the vehicle in town.

Last weekend, while I was out in the bush, i suddenly could not engage gear 5 and reverse. I stopped and looked under the car to see if there is anything i could do. I saw that 2 of the 6 bolts that mate the gearbox to the engine were missing, and one was loose. Despite this, gears 1-4 were engaging well. I found some bolts and screwed them in as a rudimentary measure just to get me to my destination about 80km away. I tried to tighten the 3rd bolt - it would screw in well, but it would not tighten.

I have spoken to my mechanic who was surprised by this. He indicated though, that it can happen, especially on older cars - gearbox bolts can work themselves loose due to metal fatigue and vibrations. He also indicated that one of the ways to rectify this is to tighten the bolts with nuts. He also visually examined the 3rd bolt that wouldnt tighten and saw that the threads were still very good indicating that maybe the threads on the gearbox or engine are the ones that are worn.

He also removed the gear sticks and cover to test the selectors and they appeared to be ok indicating that the gearbox has an internal problem.

I thus have 2 questions:

1. Is it really true that bolts can work themselves loose to the point of falling off?

2. What would cause the gearbox to suddenly fail to engage gear 5 and reverse? (we havent opened the gearbox yet - am a little short of cash... :( :( )

Any help that i can will be greatly appreciated.

Regards

Lemmyb