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Tank
9th June 2008, 04:40 PM
Gearbox problems SIII, Advice needed
My son, has a 1980 SeriesIII 109 2.25D, he has replaced clutch Master and Slave cylinders, BUT he is still having troubles changing 1st to 2nd and 2nd to first, crunching synchro's, OK if he double clutches.
Also has a hard time getting into 4th (Top) once over 60Klm/h, under that speed, no problems. Gearbox runs 90 grade Gear oil.
Plenty of oil in Gearboxes.
My 1975 Series III 2.25D 109 has Auto trans fluid (ATF) in it's box, as I have not driven it yet, (still rebuilding engine), I can't comment on what difference ATF makes to gearbox changes and longevity of gears and bearings over the standard EP90 gear oil. Anyone with any experience with different oils and the problems my son is having, I would be much obliged for any help in this matter, Regards Frank.

https://www.aulro.com/afvb/images/imported/2012/09/1339.jpg
isuzurover
9th June 2008, 04:49 PM
1st up, series boxes SHOULD run 90w GL4 gear oil (most standard gear oils are GL5 rated). Running a GL5 oil MAY cause excessive wear/deterioration of the phosphor bronze parts over time.

However - not related to the current problem.

How much actual clutch depression is he getting at the pedal - i.e. when you press the clutch, you can feel when the slack/freeplay is taken up. After that, you need a good few inches of travel with a solid pedal.

Sounds very strange, it really sounds like a clutch problem. But the change to 4th should be pretty easty even without a clutch.

It could be a selector issue (easy to check - just need to remove the box top cover) - but that wouldn't explain the crunching...
Tank
9th June 2008, 05:18 PM
Clutch is releasing OK pedal travel adjustment spot on, I told my son to check the gear change mechanism and selectors first for any signs of wear, do you think ATF in my box would cause any problems, I'm wondering why the previous owner used ATF, Regards Frank.
isuzurover
9th June 2008, 06:18 PM
Clutch is releasing OK pedal travel adjustment spot on, I told my son to check the gear change mechanism and selectors first for any signs of wear, do you think ATF in my box would cause any problems, I'm wondering why the previous owner used ATF, Regards Frank.

I don't know why he would use ATF - maybe he thought it would help the synchros. Rick is the expert, but ATF is AFAIK about the same as running 70W75 or similar oil. Some ATF is GL4.

I tried VMX80 in my IIA, didn't make much difference and didn't help the oil staying where it should (the series selector mechanism isn't the best at sealing).
Aaron IIA
11th June 2008, 07:57 PM
Also has a hard time getting into 4th (Top) once over 60Klm/h, under that speed, no problems.


https://www.aulro.com/afvb/images/imported/2012/09/1339.jpg

You seem to be over-reving the engine. You should be able to get into top gear at about 20MPH (32KPH) on the flat, and should definately be in top gear by 30MPH (48KPH).

As for the first and second problems, perhaps the synchromesh rings are worn, or the synchromesh springs are worn/broken. This could also be making it hard to change into fourth at such high speeds. I would just double de-clutch and make it a bit easier for the synchromesh.
Aaron.