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As I remember I found somewhere here in BB that Red Line MT 90 GL4 was the best oil for this transmission
Well maybe, but Alfa owners certainly weren't using synthetic gear lubricants in 1975, and their synchronizers didn't grind. But admittedly that's not to say that your lubricant is the problem.
 

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Discussion Starter #22
Well maybe, but Alfa owners certainly weren't using synthetic gear lubricants in 1975, and their synchronizers didn't grind. But admittedly that's not to say that your lubricant is the problem.
I understand your point and I agree that viscosity of synthetic Red Line seems to be very thin in comparison with SAE 90 gear oil. Change of oil with a conventional one is on the troubleshooting list also but really I can't put in which priority...
 

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But Mad North-Northwest
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The gear oil isn’t your problem. Gear oil won’t cause grinding into reverse: your clutch is not releasing.

Synthetic is fine, lots of folks here use synthetic Redline 75W90NS.

MT90 is the proper weight but it’s GL4 instead of GL5 so it uses different EP additives. I’ve tried it, it works fine, though probably not my first choice.
 

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Discussion Starter #25
So, I did some break-in to smooth the contact between clutch disc and flywheel. The improvement was very obvious as all 5 gears work almost fine now. With the assistance of my son in driver's position I did test in all 5 gears car with the car raised and definitely the clutch is working perfect, i.e. with the engine running in 4th gear (which actually locks main and secondary axles) with the clutch engaged I was able to keep the central shaft by hand and to turn it in any direction. Regarding reverse the grinding now was much reduced when I tried the engagement just after pressing clutch pedal and it was completely eliminated when I was waiting a few seconds with the clutch engaged before select reverse. I think that Red Line MT 90 is quite "thin" and permit secondary shaft to maintain some rotational speed due to its inertia thus the grinding not appeared if I was waiting let's say 5 seconds. A "thicker "oil like SAE 90 may absorb faster the inertia rotation energy of secondary shaft thus enabling normal engagement of reverse gear. Tomorrow I will try conventional SAE 90 oil (as per original spec) and I will let you know the outcome.
It seems that my problem had 2 causes, not complete disengagement at the beginning plus gear behavior with Red Line. As for the proper oil specification I think that GL 5 is not suitable for the bronze alloy of fork selectors, so I will stay with GL 4.
 

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But Mad North-Northwest
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Well, glad you figured it out.

I think you're misunderstanding how gear oil viscosity is characterized. MT90 is a 75W90 multigrade. This has the same hot viscosity as 80W90 or a straight 90, it just doesn't thicken up as much when cold. Once the transmission heats up they are all the same viscosity.

Your problem with reverse happens in every Alfa 5-speed and isn't indicative of a problem with the gear oil. Reverse is not synchronized: the grind fix is either to wait a few seconds after pushing down the clutch for the gears to spin down, or to touch another synchronized gear before shifting into reverse.
 

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Discussion Starter #27
A post above talks, I think, about lubricating the input shaft splines. I've never heard of this before. Any material will end up on the clutch disc due to centrifugal force as the assembly spins.

The next issue is the gearbox hanging on the input shaft ...

Ignoring the fact above 2 concerns, I'd put the rear wheels safely up in the air and start the car in gear and using the brakes and clutch pedal see if any bedding in car help

Good luck
Pete
Splines lubrication is just a greasy touch to make assembly just slippery. I already did as you said... if you see my previous long post is self explanatory.
 

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Splines lubrication is just a greasy touch to make assembly just slippery. I already did as you said... if you see my previous long post is self explanatory.
Yes, we must have been posting at the same time. I deleted my post after seeing yours.

Glad you are making positive progress:)
Petr
 

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Discussion Starter #29
Well, glad you figured it out.

I think you're misunderstanding how gear oil viscosity is characterized. MT90 is a 75W90 multigrade. This has the same hot viscosity as 80W90 or a straight 90, it just doesn't thicken up as much when cold. Once the transmission heats up they are all the same viscosity.

Your problem with reverse happens in every Alfa 5-speed and isn't indicative of a problem with the gear oil. Reverse is not synchronized: the grind fix is either to wait a few seconds after pushing down the clutch for the gears to spin down, or to touch another synchronized gear before shifting into reverse.
It seems that you are fully right! Of course reverse is not synchronized, so as far as the clutch disk and flywheel found themselves in harmony the 5 gears behave normally and certainly reverse need a gentle handling. For many years in automatic it seems that I forgot the kindness that reverses gear is asking! Regarding oil I will check tomorrow the traditional way thus to have the comparison ready for judgement!
 

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But Mad North-Northwest
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Yeah, it's an interesting experiment to run, and I've tried a lot of gear oils. I successfully used the OEM Shell Spirax HD90 and it worked fine, just impossible to find in the US now. Lots of people here have been happy with Redline 75W90NS. Best I've personally found is Swepco 201, but not many other Alfa folks use it.
 

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It was just the arm I replaced, the link from pedal to master cylinder I can't explain why it fixed the issue but it did
 

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Reading your adventure, I realized that during assembly of the gear box ( I did myself alone under the car) I had, for a while, the hole transmission hanging on its input shaft partially inserted to the engine part, which in turns may had as a consequence to bend the input shaft(!) but can this happen so easy?
We know something is rotating shaft while engin.e ruining , Pilot Bering my guess drag in pilot shaft . bearing ****ed from trans hanging .
 

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I recently had a warped pressure plate. An initial OVER depression of the pressure plate bent a spring such that future depression of the clutch would not fully disengage disc from flywheel.
 

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Discussion Starter #36
As I confirmed earlier clutch setup works fine. After filling with a little heavier oil (Liqui Molly 85W90 GL4) the situation improved further and reverse is engaging smoother as heavier oil absorbs reverse gear spin during clutching. As soon as the car will be on the road and clutch break-in complete in real conditions I think everything should be fine!
 

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Discussion Starter #37 (Edited)
I recently had a warped pressure plate. An initial OVER depression of the pressure plate bent a spring such that future depression of the clutch would not fully disengage disc from flywheel.
I see... I have a complete new clutc set by Sachs and fortunately I don't have such a
problem!

Thank you all for you help and advice!
 

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Your problem with reverse happens in every Alfa 5-speed and isn't indicative of a problem with the gear oil. Reverse is not synchronized: the grind fix is either to wait a few seconds after pushing down the clutch for the gears to spin down, or to touch another synchronized gear before shifting into reverse.
Old racing trick with a 105 Alfa is to put into 2nd gear just before selecting reverse. You will find it slides smoothly into reverse. Mechanical sympathy goes a long way in any gear......
 

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It is possible the flywheel ring surface was machined too deep or not true causing the clutch plate to not be parallel to flywheel surface. Also I have witnessed, if the clutch plate was not tightened down concentrically, the pressure plate springs can warp causing the same problem.
 

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Old racing trick with a 105 Alfa is to put into 2nd gear just before selecting reverse. You will find it slides smoothly into reverse. Mechanical sympathy goes a long way in any gear......
I haven't tried to go from N to reverse WITHOUT first cycling into second since I rebuilt my '71 Spider gearbox. Works like a charm, every time. Much less embarrassment leaving the parking lot without the R gear crunch!
 
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