Conversion from automatic to manual gearbox.. Part 3

In part one the engine was removed, part two saw the manual gearbox, pedals and gearlever go together and finished with gear oil making a large puddle on the garage floor.

Oil seemed to be pouring out of the gap between bellhousing and the engine, at first i thought that the sump gasket has gone as the oil looked pretty dark, and set about taking the sump off, replacing the gasket and putting it back together again. Another test run saw the problem persist and I realised the gearbox was leaking a LOT of oil. At this point it looked like the box itself had lost a seal so had to come out again. I couldn't face taking out the whole engine again so decided to split the bellhousing from the block in situ and drop the whole thing out.

All I can say about this is don't bother! in a 5a there isn't much room to play with, you have to simultaneously tilt the engine up whilst slanting and rotating the gearbox down, trying to catch 100 odd kilos of cast iron box and bellhousing is not fun. Unless you have access to a ramp or lift its much easier to remove the engine and box in one and split on the crane or garage floor.

With the gearbox off the problem was pretty obvious, one of the bellhousing to gearbox bolts had stripped its threads, for some reason these bolts go straight through the gearbox casing and if loose can allow gear oil to leak out. The image below shows which one caused all of the trouble.

   click to enlarge images

After removing the overdrive I took the box to a couple of local engineering firms to try and get a helicoil fitted, no one had a milling machine large enough to drill out the old thread. Instead I ordered a helicoil kit online. After some head scratching I worked out that the thread size was 7/16 BSW. The kit comes with a drill, tap, helicoils and insertion tools, see pictures below.

   click to enlarge 

Drilling was very carefully done with a hand drill at a slow speed stopping every few minutes to make sure too much heat wasn't being generated. Once the hole is the correct size the tap is used to cut a thread into which the helicoil will screw into, this was also a slow process with plenty of lubrication and backing off every few turns before continuing. The helicoil is screwed in and held pretty securely. Once the bolt is screwed back in it is supposedly stronger than the original thread. Not wanting to test this I was careful when tightening it all up.

After the whole lot was reassembled and the engine reinstalled a very nervous test drive showed that the gearbox was holding oil, there was a weep from the overdrive gasket but until it gets a lot worse I am leaving well alone.

I still have some of the 7/16 BSW helicolis left if anyone needs one drop me an email and I will lend the kit.