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1-2, 2-3 bad synchros, 1980 FS5W71B 5 speed, buying time, Swepco/ATF or MT-90?


NewZed

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I just installed a used 1980 5 speed in my 76 and find that the 1-2 and 2-3 synchros are worn. At high RPM I get a quick one to two notch grind, and a full-on grind if I try to shift fast. "Normal" low RPM shifting is fine. I had a 78 5 speed that had a similar problem, using 75-90W Valvoline gear oil, and the problem was fixed by switching to Red Line MT-90. But I started with MT-90 here and am out of easy options.

 

Any thoughts on ways to buy some time or get a few hundred more RPM over the MT-90 oil? I've seen that the Swepco 201/ATF blend is popular but don't know if it will help or hurt a bad synchro problem, compared to Red Line MT-90.

 

In the long run, I'll probably swap synchros from another trans (maybe, I haven't had a transmission apart yet) but I just put this one in and haven't built up the urge to take the car apart again yet. It's the quietest, smoothest tranny I've had in the car, except for when I turn things up.

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I think the SWEPCO is worth a shot. You might try it full strength and 50/50. I've converted people with the steel synchro'd comp transmissions to SWEPCO from Redline, but haven't done a brass synchro back to back, so I'd be really interested to see what you think of the two as compared to each other.

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Thanks Jon. If it hasn't been tried, I might as well give it a shot, for the record, in comparison to MT-90.

 

I found a local Porsche racer who just got back from Sears point and was nice enough to hang out at his shop until I could beat the traffic and get over there. He poured me two quarts from his 55 gallon drum, but labeled it Swepco 210 80W-90W (not 201). According to the internet, apparently the 210 grade is popular with some of the sports car crowd also, so I have an unknown. He had just driven 14 hours today after the weekend races so must have a been a little bit punchy. It's a dark bluish green color. It didn't pour like an 80W-140W so I'm guessing it's 201 since he labeled it 80W-90W.

 

Either way, it's in and I'm just waiting for the Halloween candy scavengers to get off the streets so I can give it a test drive.

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Confirmed that the Swepco is the 80W-90W 201. It's definitely better, in this old, worn wrecking yard transmission, than the Red Line MT-90 I had in there. Took away the 1-2 notchy, partial grind and moved the 2-3 grind up about 800 RPM. It also feels less metal-on-metal and more cushioned when it happens, plus fewer teeth per grind. Still needs a rebuild but I won't be grinding unless I use the extreme upper end of the tachometer now.

 

Not the miracle work that I saw with a 78 5 speed going from Valvoline 75W-90W to MT-90, but still worth doing to buy some life for the synchros. Results in a tight tolerance, newly rebuilt transmission might be totally different. If I try the 50/50 blend, it will be later, I'll ride with this for a while.

 

Thanks for the conversion. Choosing gear oil for synchros is like voodoo.

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I think the SWEPCO is worth a shot. You might try it full strength and 50/50. I've converted people with the steel synchro'd comp transmissions to SWEPCO from Redline, but haven't done a brass synchro back to back, so I'd be really interested to see what you think of the two as compared to each other.

 

What brand of ATF did you use? Might as well finish the experiment and try to get a little more, the SWEPCO 201 alone was a benefit.

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  • 2 weeks later...

GM synchromesh is an excellent fluid for our old brass synchro transmissions. It helped shifts enough to get rid of a 3rd gear grind in a 79 transmission I had. Search the forums for it and you will find some excellent info on it. Pennzoil makes an equivalent, and it's inexpensive. I use it in all my transmissions now.

 

Swepco is also good, just a bit harder to get a hold of, and more costly.

 

I found the thread:

Synchromesh

Edited by rejracer
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rejracer, I missed your post, I'm just seeing it. I'll check out the Syncromesh, it sounds interesting.

 

In the meantime I tried a 50/50 blend of Valvoline Dex/Merc ATF and Swepco 201. It made the drop in to gear easier for relaxed driving but I lost a couple hundred RPM on the gear-grind limit when in a hurry, and it was noisier when it happened. I drained the 50/50 blend and re-mixed the Swepco 201 I had taken out, to give a 25% ATF blend. That made a significant difference and it feels like the best it's been, about the same as the 100% Swepco. I think that 50/50 was just too thin for the worn parts.

 

I ordered some parts, inserts and springs, from Courtesy Nissan and will probably just use what I have before opening the transmission to see what I can improve, unless GM's Syncromesh sounds amazing. Thanks for the tip.

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How about some details?!!! Which brand, GM, Amsoil, Pennzoil? What were you running before?

 

My take, from the internet, on the GM Synchromesh was that it was pretty low viscosity, about 30W, and was designed more toward the transmissions that run ATF, like some of the Borg Warner's. A good before and after story would be interesting.

 

Thanks.

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I was initially running swepco, when during some aggressive driving I tore up the 3rd gear synchro. 3rd synchro was always weak from that point on. I switched to GL-4 and it did the same thing. I drove the transmission like that for about 7 years. After reading about the synchromesh I tried it and the 3rd gear grind went away. I used the Penzoil variant of Synchromesh, I believe they are all the same.

 

Synchromesh is a thinner fluid for sure. I did notice a bit more bearing noise while in neutral, but no noticeable noise increase when driving. I don't know if this is a good fluid to use long term in these transmissions or not, so I'm experimenting with it. Since I put the fluid in ~ 2 years ago I've put on ~ 5000 miles. I did do one road trip which was about 400 miles one way, I was a bit concerned being it's not the factory fill. Lots of freeway driving along I5 which translates to cruise speed of 75 to 80mph for the majority of the trip.

 

I can attest to the fact that this fluid shifts much better than GL-4 fluids. I've never run swepco back to back with Synchromesh, but I remember swepco being very good as well.

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What? Another option?! I hadn't considered that Nissan might have their own transmission fluid, although I had my Pathfinder transmission fluid changed at the local dealer years ago (when I had less free time than I do now) and I remember noticing that the shifting was stiffer and notchier when I got it back. I wondered how the dealer fluid was different from the factory fill fluid but never followed up on it.

 

Thanks for the details rejracer. The Pennzoil Synchromesh doesn't seem to be stocked by anyone in my area. The GM dealer has the GM brand at $17.95 per quart. So far, the 25/75 ATF/ Swepco 201 blend I'm using has raised the aggravation threshold to where I can live with it for a while.

 

Synchromesh, Swepco and Nissan fluid seem like good options. Better than MT-90,which looks better than Valvoline 75-90W. Ranking based on a small set of experiences. How can a simple thing like oil get so complex?

Edited by NewZed
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Another option as well ;) I had an Mitsu Evo some years ago which can only use GL4 transmission oil. I was able to get some as well at the dealer. They filled up some empty bottles to provide me some.

Edited by Lazeum
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  • 3 months later...

A followup on the 25:75 ATF:Swepco 201 blend in my wrecking yard 1980 5 speed - the transmission must have had some minor rust, corrosion or "varnish" on the synchros or bearings. After a few thousand miles with the ATF/Swepco blend, it works like a normal transmission. The synchros work fine now, no more grinding or notchiness, even at high RPM. Just using all it would give, it slowly got better and better. The bearings aren't dying either, still quiet.

 

I never took it apart and don't know the usage or maintenance history so can only guess at what the original problem was. It might even have been freshly rebuilt and the synchros needed to wear in. The clutch released fine. Maybe the pilot bushing was tight on the input shaft? Didn't seem so when I installed the transmission. Maybe the Swepco blend has magic healing powers.

 

 

On the Synchromesh variants: I found this onthe Swepco web site - http://www.swepcolube.com/products/swepco-717-synchromesh-transmission-fluid - it's been around for a while, apparently, but I've never seen a report of anyone trying it. The links on the web site are screwed up so you can't really see any technical data.

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