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Discussion Starter #1
Evening all,

I replaced my gearbox oil two track days ago with torco MTF, the car has probably done 200 road miles since and then 2-3.5 hours of track work at quite a fast paced circuit.

The day after i swapped the gearbox oil i drove 50 miles to the track and then got one with my day noticing that every now and then i'd get a small crunch shifting from 3rd-4th. This had never happened before with the old MTF i was using.

I then did a 100ish road miles and went on my next track day, when i was on track progressively throughout the day i started getting a crunch from 4th into 3rd downshifting of which got worse throughout the day. The track is fast so there is no 2nd gear corners, but naturally on the road at high revs shifting from 2nd to 3rd its crunching like my morning cereal.

Has anyone else had this 'problem'? The box was shifting okay before, i never heard or felt a peep from it yet ever since i put the Torco MTF in it its started crunching quite badly now.

This was the oil i was using before...
Smith & Allan MTF 94 Gear Oil | Buy oil, lubricants, greases and more from Smith and Allan

I have since bought a master rebuild kit from syncrotec and an M factory plated diff as it was on the list to do anyway. I will put the old MTF i used in it from before to see if i can enjoy the car for the last few weeks of summer, but im just curious as i planned to use Torco RTF in the box once its built.

I hasten to add that 2.5 years ago i had the box to bits to replace a snapped shifter fork and add a 4.4FD. I inspected and ensured the syncros, and shifter forks were in spec. It has probably done around 10,000 miles since then.

Any ideas would be great,

Lee
 

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\/Your Mom Was Here\/
Vibe GT
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4,833 Posts
The stuff you have listed is gear oil, AKA 90 weight. Honda prefers 30 weight motor oil or the like (syncromesh or Torco fluids). 90 weight is too thick of oil and may have hidden a problem for a while and also may have caused more!

The product can be used in a variety of synchronised manual transmissions where a 75W-80W or 80W manual transmission oil meeting the API GL-4 performance level
 

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Brokedick Millionaire
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The stuff you have listed is gear oil, AKA 90 weight. Honda prefers 30 weight motor oil or the like (syncromesh or Torco fluids). 90 weight is too thick of oil and may have hidden a problem for a while and also may have caused more!
You don't know about viscosity do you?

A common misconception about gear oils relates to the SAE rating of the product, what most people don’t realize is that the SAE classification for gear oil and engine oils are different! The most common mistake is the belief that the viscosity of SAE 80W gear oil is much thicker than the viscosity of SAE 10W-40 motor oil. This is absolutely incorrect! A 10W-40 motor oil’s viscosity is actually similar to the viscosity of 80W gear oil, and the viscosity of SAE 10W-30 is similar to 75W gear oil.
 

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Wonder what else he doesn't know about...? ;)

Why did you change the oil in the first place?

Third Gear synchro often wears out, I've seen it first hand with Synchrotec Carbons!
 

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\/Your Mom Was Here\/
Vibe GT
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Yes I do know this... and I somehow knew someone would chime in with that. I know redline MTF will wreck a input shaft bearing, what about gear oil, does it contain those same additives in it or why aren't we this gear oil in all our trans?
 

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I made the mistake of running 80/90 gear oil in my s20 Trans once. thing became a bear to shift but once I moved back to a 10w30 motor oil it shifted like a dream. if the weight is off by a large enough amount. it wont shift correctly. I did read Bones post as well. But I do think there is a big difference in what I tried to run vs what the factory recommends.
 

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Discussion Starter #7 (Edited)
I changed the oil cuz it had a few 1000 miles on it and 3 track events so it was probably due a change.

I used torco mtf after doing a few hours of reading and saw numerous posts by bone and fina saying how much better it is than the now reformulated honda mtf. I trust both there judgements so thought I'd give it a try. I'm just curious as to why it's caused my box to crunch.

The smith and Allen oil I used before said it was suitable for my box so I took its word for it. I was a little coy when first putting it in as it did have a slight smell of regular gearbox oil, where as mtf does not. However it seems to have worked well. Suppose the decider will be when I tear the box down.

Also I'm well aware of 3rd gear going but it was absolutely fine before I swapped oils. I've put regular gearbox oil in a Honda box before when my skills weren't up too much, it immediately starting eating 3rd gear and when I tore it down it wasn't pretty. The oil was black and like treacle, the old oil when drained was still clean and flowed well like mtf.
 

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Brokedick Millionaire
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I have three fluids I avoid.....

Redline MTF and MT90, seems the ATF attacks the plastic cages.

Honda current MTF, pisswater thin.
 

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Discussion Starter #9
So strange thing happened yesterday...

Went to a local meet and there always something to play with on the drive home and the box was faultless, no crunching in any gear. I'm a little baffled by it, nothing has changed on the car.

The only thing i can think of is the temperature last night was around 10 degrees/50F cooler than the last 2 times i've driven the car.

Any ideas? Oil thinning out when it gets too warm...
 

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RTF is very slippery. If your synchro is worn near the service limit or gear cone glazed, you will have shifting issues.
 
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