Now moved to the appropriate section:

Hi folks

Long story short, replaced gearbox oil (1.0 litre flush) then added the specified amount per Ford specification with cross check against Haynes manual for the 1991 Ford Sierra 2.0i MT75 Gearbox.

As the clutch cable was stiff, I removed it, then soaked overnight in WD-40 which freed it up immensely. Refitted, car ran grand.

3 days later, noticed a clunking when depressing/releasing the clutch pedal followed by difficulty getting into 2nd gear (spongy feeling). 1st, 3rd, 4th, 5th all in that order were trouble free.

When in second gear it would be grand until you released the gas pedal, then 2nd gear would pop to neutral.

A few days later, 4th gear started showing the same intermittent symptoms. Still, 1st, 3rd, 5th all good at this stage.

Then started to noticed longer cranking to get the engine to start one morning, where the car, once it started seemed to shake and now I'm experiencing this on a daily occasion when starting with a resulting clunking/whirring noise from the gear box.

Going to add video footage which captures the sound as going through the gears (where you can see me holding 2nd gear longer than normal to prevent it popping out).

Also, up to this stage, reverse was error free, but now, following on from the gradual reduction in 2nd and 4th keeping in gear, Reverse is roughly showing a 50:50 rate of going into gear.

No grinding of gears noticed over any of this. So not sure whether having replaced the gear oil, cleaning the clutch cable if this has somehow allowed gremlins of some sorts to appear out of nowhere.

Car now has 220,045km on it and I look after it irrespective of the costs involved.

Going to remove gearbox Saturday and replace the clutch kit and release bearing so hoping for the best!

(Just a side note, car is LHD and is sporting a MK4 Golf Gama radio and CD player and the engine in neutral runs smoothly, no rattles, all new engine bushes and gearbox mounting, center prop shaft bearing, donut bush and rear differential serviced)

Curious if any other people have experienced the same, or a similar occurrence?


Added new text based on previous location where initiall posted:

I used silicone spray afterwards to (which i forgot to mention in the post) once the bath of WD-40 worked as that removed a lot of internal dirt in the cable.

Gear oil used was Liquid Moly 75W - 90 based on the old Finis code from Ford.

No records exist in the comprehensive service history that came with the car, pre-2015 when i bought it. Had a clutch fitted by a mechanic back in 2015 as it was slipping at that stage who was supposed to have replaced the gearbox oil at that time but I can't be sure if he actually did that part of the request despite providing him gearbox oil at the time as the oil was pretty much a deep dark brown when removed.

 

MT75 gearboxes don't like 75W 90 oil. Originally Ford had their own specific MT75 oil, the colour and consistency of ATF. I put Ford 75W 90 oil im one of mine once as that what was what the dealer told me they now recommended as they stopped doing MT75 oil. It was horrible and notchy and slow to engage gears. I immediately dropped it out and put Comma MT75 oil in and it was fine. Granville also do an MT75 oil.

 

ah bugger so good chance then I’ve totally destroyed the gearbox as a result?

I can’t seem to get either brands you mentioned over here in Munich and the AUTODOC website where I got the 75W stated it was replacement for the original Ford spec. That could make total sense as it was only after I had changed the oil that the rumbling grinding sounds began. So in most cases it’s probably destroyed the needle bearings or the likes inside the box. And early today I bought another MT75 north of Nuremberg that I need to collect later this week thinking I’d need to change the gearbox out.

Oh well!

 

I changed oil to my mt75 gearbox and I put inside kroon oil which meet the spec of ford. Colour is red. Gear changes are perfect, smooth.

 

When I replaced the 75W 90 with MT75 oil, everything became peachy again, no lasting damage so you could be alright.

 

Half people say use 75w90 synthetic oil,half people say use ford mt75 oil. Personally, if the gearbox is std, I would use MT75 oil.

 

Cheers folks for the info on the MT75 oil.

finally managed to source some here in Germany and refilled the gearbox last weekend. Gears are working nicely again and narrowed down the other gearbox related noise to the needle bearing and ball bearing kit behind the flywheel so waiting on those parts to arrive from the uk later this week and will fit once here.

never a dull day with old cars.

 

Good news mate.