Manual Transmission - what gear oil?

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canucksafari

canucksafari

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I was going to change out the tranny oil today with Castro Syntec from Wallymart. Can't beat the price but ... then I got reading and now am pretty much totally confused (and procastinating). Some say only use sythetic gear oil designed for synchro transmissions because it needs the modifiers for the synchros to work right. Others say don't use synthetic gear oil for transmissions because it has the modifiers for LSDs and will screw up the tranny. I had wanted to put synthic in just for smoother shifts when is is cold and to be able to get going right away when its real cold. Below -15C it can be a pain to even get 1st gear unless I let her idle for about 5 min or more at 1400 rpm.

So I thought I'd ask the guys I do know rather than going by the conflicting advise in the outernet from people I don't know. FSM only says 75/90 GL4 for the tranny and T-case and 80/90 for the difs but nothing about synthetic oils So, which synthetic oil for the tranny do I get and where do I get it? Or should I just put in some more dino 75/90 and put up with a cold tranny issues.

Right now I have a jug of dino 85/140 for the rear lsd (with as tube of the lsd friction modifier) and a pail of dino 80/90 for the case and front dif.
 
Dino gear oil is 80/90W and synthetic gear oil is 75-90W. As you know nothing beats synthetic oil for keeping viscous at low temperatures. So for cold weather starts, synthetic is the way to go.

However most synthetic gear oils are GL5 and our old trannies want GL4, which is an older grade. I have found that GL5 is more slippery than GL4, which does not allow the synchromesh’s to spin properly and you can get gear clip between shifts. The only synthetic GL4 gear oil I know of is made by Red Line – its called MT90, buts it very pricey. I use Chevron synthetic 75-90W, which is a GL5 oil and I shift slowly to allow the syncros to catch up. However, I still occasionally clip gears.
 
I bought 18.9 l (5 US gallons not 20 l) of Chevron syn 75-90 (GL5) for about $160, which is about $8.80 per litre. I use this in the trans, transfer and rear diff and dino in the front diff as it gets used much less.
 
canucksafari said:
I had wanted to put synthic in just for smoother shifts when is is cold and to be able to get going right away when its real cold. Below -15C it can be a pain to even get 1st gear unless I let her idle for about 5 min or more at 1400 rpm.
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Ya I was thinking of going all syntytic this year too, as the shifter is hard to move at -40 with the 80/90, I had to train the :princess: to jam the tranasfer in neutral and jam it in gear while warmin the truck up as the cruiser is now her daily driver.

You guys think the 75/90 GL 5 stuff won't work..... I think I ll have a hell of a time trying to find anything else up here,
 
jfc said:
You guys think the 75/90 GL 5 stuff won't work..... I think I ll have a hell of a time trying to find anything else up here,
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GL5 will work in the t-case but as Glenn says, you have to be careful with your synchros. But try the Amsoil stuff I put up in the link of my other post:
mtg_75w90_medium.jpg


It is a GL4 synthetic oil specially made for our trannies. I called a local rep. He doesn't have any in stock so will either call some more local reps today or order from their online store. The local guy told me it was just over $14 a bottle. I need 4 of them for my tranny. My t-case is chain driven so good old 80/90 is all I need there and for the front dif.
 
Mopac carries the Red Line stuff, prices aren't too bad there.
CT (at least my local CT) has Red Line, but a pretty limited selection.
 
canucksafari said:
GL5 will work in the t-case but as Glenn says, you have to be careful with your synchros.
Click to expand...

Not for me, my seal is gone between the transfer and trany, so all my oil get sucked into the tranny, so I tapped both the fill bungs and connected them with some stainless line:grinpimp:(only part of the cruiser not rusty), to let the oil flow back,

I'll take a look at CT
 
canucksafari said:
So, which synthetic oil for the tranny do I get and where do I get it?
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Norm beat me to it: Redline MT90 at Mopac off 200th. Syth, GL4 75/90.

Glenn-BJ74 said:
I bought 18.9 l (5 US gallons not 20 l) of Chevron syn 75-90 (GL5) for about $160, which is about $8.80 per litre. I use this in the trans, transfer and rear diff and dino in the front diff as it gets used much less.
Click to expand...

That's what I had in all the same places. The H55F did not like it (slightly notchy shifting). Put MT-90 in the H55F, and maintained the Chevron syn 75-90 in the rest.
 
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Greg_B said:
Norm beat me to it: Redline MT90 at Mopac off 200th. Syth, GL4 75/90.



That's what I had in all the same places. The H55F did not like it (slightly notchy shifting). Put MT-90 in the H55F, and maintained the Chevron syn 75-90 in the rest.
Click to expand...

I thought about using MT90, but the H55F takes 4.9 litres, which is 5.2 US quarts. ( 1 US quart = 0.946 litres) The stuff is sold in US quarts, so 6 X $12 or $16 = $72 or $96 per change out. Too expensive for me.

Does any one know of a dino 80-90 GL4, I could mix (maybe 50:50 with the Chevron syn 75-90, which would solve the problem, much cheaper than going MT90 or Amsoil.
 
Glenn-BJ74 said:
Does any one know of a dino 80-90 GL4, I could mix (maybe 50:50 with the Chevron syn 75-90, which would solve the problem, much cheaper than going MT90 or Amsoil.
Click to expand...

Chevron 80-90W. Last time I asked about it at the Frieghtliner dealer, they told me the syn. and dino were blendable with each other. Last time I bought a pail it was about $90 CDN. I don't know off hand if it's GL4 spec. , but I run it straight in the whole drivetrain without problems (yet) except of course for hard shiftin' in cold weather until the Xmsn warms up.
 
Is there any syntetic stuff I can use for the brake fluid for the cruiser and dodge, and power steering for the dodge,
 
jfc said:
Is there any syntetic stuff I can use for the brake fluid for the cruiser and dodge, and power steering for the dodge,
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You can get the DOT 5.1 brake fluid (silicone based brake fluid). Was doing some reading about it a while ago. The good is it doesn't attract moisture, doesn't eat paint, and has a much higher boiling point. The bad is that it tends to slip past seals of brake systems designed for DOT 3 or 4 brake fluid. The bad is enough for me to keep on using the old stuff for my brakes and clutch.

Synthetic power steering fluid is just synthetic ATF. Redline and Amsoil makes it as does a lot of other manufacturers. It is the only stuff i can use in the tranny of my other Safari - except Nissan Matic Fluid ($$$). If leaks are your problem or the power steering pump is whining away, try the Lucas Power Steering Stop Leak. On my wife's Tercel, it was constantly loosing fluided and the pump was whining away. I bought a bottle of this stuff and just started topping up the power steering with it. I went through half a bottle before the leak stopped. The power steeing pump whining stopped after the second top-up. Its been over two years since doing it and the power steering system is about the only thing that doesn't leak on the Tercel. Amazing stuff.
 
Helomech said:
Chevron 80-90W. Last time I asked about it at the Frieghtliner dealer, they told me the syn. and dino were blendable with each other. Last time I bought a pail it was about $90 CDN. I don't know off hand if it's GL4 spec. , but I run it straight in the whole drivetrain without problems (yet) except of course for hard shiftin' in cold weather until the Xmsn warms up.
Click to expand...

Most 80-90W are GL4 and GL5. I am looking for a GL4 only, which is an older grade.
 
canucksafari said:
You can get the DOT 5.1 brake fluid (silicone based brake fluid). Was doing some reading about it a while ago. The good is it doesn't attract moisture, doesn't eat paint, and has a much higher boiling point. The bad is that it tends to slip past seals of brake systems designed for DOT 3 or 4 brake fluid. The bad is enough for me to keep on using the old stuff for my brakes and clutch.

Synthetic power steering fluid is just synthetic ATF. Redline and Amsoil makes it as does a lot of other manufacturers. It is the only stuff i can use in the tranny of my other Safari - except Nissan Matic Fluid ($$$). If leaks are your problem or the power steering pump is whining away, try the Lucas Power Steering Stop Leak. On my wife's Tercel, it was constantly loosing fluided and the pump was whining away. I bought a bottle of this stuff and just started topping up the power steering with it. I went through half a bottle before the leak stopped. The power steeing pump whining stopped after the second top-up. Its been over two years since doing it and the power steering system is about the only thing that doesn't leak on the Tercel. Amazing stuff.
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thanks john,

maybe i keep using two feet to stop the truck then,

but i'll giv that lucus stuff a try becase the steering pump is leaking...:hhmm: how did you know? I guess it is a dodge part eh ;p
 
jfc said:
maybe i keep using two feet to stop the truck then,

but i'll giv that lucus stuff a try becase the steering pump is leaking...:hhmm: how did you know? I guess it is a dodge part eh ;p
Click to expand...

What, no power assist brakes??? Feet dragging out the door doesn't count. :hillbilly: How old is the brake fluid? If it's been in there a while, then it is worth it to buy a jug of brake fluid and flush the whole system - from the back forward. New brake fluid can make a big difference.

As for leaks, everything leaks fluids - eventually. The only vehicles that I have had which haven't leaked were the old Nissan van and so far the Safari. All my Toyotas cars have leaked and the VW diesel leaked lots. The old 76 Chev 3/4T leaked everywhere including the gas tanks. I have a bit of experience on cheap and easy ways to stop leaks and a few on not so cheap and easy ways when the former doesn't work.
 
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