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1969_Mach1

4sp Toploader Gear Oil

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Basically, what gear oil are members here using in their toploader 4sp transmission?  I initially filled mine with Lucus 80W-90 after a rebuild and it shifted great, smooth, was quite.  But read that GL-5 rated gear oils are bad for the brass parts and GL-4 rated gear oils should be used in these transmissions.  I drained it and refilled it with Joe Gibbs Racing 80W-90 GL-4 rated gear oil.  The trans is much harder to shift, especially downshifts from 3rd to 2nd.  Are the GL-5 rated oils truly bad for the brass parts in these transmissions?  Amsoil makes a synthetic 75W-90 GL-4 rated oil, but before I change the trans oil again I am curious what others are using?

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Thanks.  I can mail order the PennGrade from Summit Racing.  Apparently, that is the Brad Penn gear oil that David Kee Toploaders recommends.  I might be able to get the Sta-Lube gear oil locally.  I might try the PennGrade.  Hopefully, it will work better than the Joe Gibbs oil I currently have in it.

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I bought the PennGrade Gear Oil from Summit last fall after reading about this issue either here or elsewhere.  

Just need to drain out the GL-5 that has been in there since 2011 when I get it out of storage and pour in the GL-4.

I had bought a complete rebuild kit from David Kee and had a local guy give mine an overhaul back in 2011.   I just got the correct weight gear oil from the local auto parts store not knowing I should be concerned with it being GL4 or GL5 at the time.  

This Toploader had never been gone through before (short of a fluid change in the mid 80's) so the rebuild made a huge difference.  

However it does grind going into 2nd every once in a while, so I'm hoping a swap to the correct lube stops or lessens it … vs. having to take trans out to have my guy go through it again.

Doug  

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11 hours ago, Brian Conway said:

The stock 69, one year only,  4 speed shifter does have a troublesome reverse détente assembly.   First indication of a problem is the 3-2 downshift.   Brian

I've got an O.E. '70 Hurst Shifter on mine plus it is 1-2 up-shift only that I get the occasional grind.

Doug

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16 hours ago, barnett468 said:

There should not be a significant change in shift feel between oil, so it sounds like something is not right.

 

 

That was my first thought and I hope that's not the situation.  I would say there was definitely a noticeable difference in shifting, particularly downshifting.  I don't know where noticeable changes to significant.

I have done some research and apparently the Joe Gibbs GL-4 gear oils are formulated to flow easily and not leave much oil film on anything for less parasitic drag and less power loss.  I will say the 80W-90 Joe Gibbs oil pours easily, almost like a 50W motor oil.  The Lucus gear oil doesn't pour as easily, and leaves a slippery film of oil on everything.  But the Lucus oil is GL-5 rated and twice I've contacted Lucus and both times they have said their gear oils are not for manual transmissions that use brass synchronizer rings.  My guess is the Lucus oil doesn't have enough antioxidation properties to counteract the additional Sulphur in GL-5 gear oils.  I don't know, that technical information is hard to get.

I drained then refilled the trans with the 85W-90 GL-4 Sta-Lube gear oil that Brian Conway say's he has used with no problems.  Penngrade oil had to be mail ordered and I didn't want to wait.  I'll take the car out this weekend.  Hopefully I'll will shift (particularly downshift) a little better than with the Joe Gibbs gear oil.

For the shifter I have a Hurst Competition Plus.  Not the original 1970 model, but what Hurst now offers.  I'm not completely happy with it and would prefer the OEM 1970 type but they are extremely expensive when you find one is decent condition.  On the current model the shifter stick is not removable which makes things a little more difficult.

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4 hours ago, Brian Conway said:

Not a Hurst guy.  Brian

 

My Hurst is stealthy though with stock boot, lever & knob up top just like yours ... got to crawl under the car to see it !!

 

IMG_1262.JPG

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52 minutes ago, 1969_Mach1 said:

For the shifter I have a Hurst Competition Plus.  Not the original 1970 model, but what Hurst now offers.  I'm not completely happy with it and would prefer the OEM 1970 type but they are extremely expensive when you find one is decent condition.  On the current model the shifter stick is not removable which makes things a little more difficult.

I just started going though my old Mustang receipts (prior to 1998 when I started using Quicken).   I'm slowly putting all these old receipts in a spreadsheet by date and am up to 1988 (bought the car in 1981). 

Anyway I got this '70 O.E. Hurst Shifter from some guy selling Mustang parts and was curious what I actually paid for it.  This was the Summer of 1984 and I went to his house to look at his Mustang parts and a '69 Mach 1 project car he had for sale.

 Within my receipts I found a note saying ... Shifter FREE ... I don't show buying any other parts from this guy and I know it was NOT the shifter that I went to look at.   Maybe because the lever was all banged up or that the threaded end for the knob was snapped off I don't know why he gave it to me for FREE and I certainly did not remember this fact from that day and seeing the note recently certainly did not jog any memory either.

Thought I'd share,  

Doug

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On 3/29/2019 at 5:59 AM, stangs-R-me said:

I've got an O.E. '70 Hurst Shifter on mine plus it is 1-2 up-shift only that I get the occasional grind.

Doug

If you are using the correct oil then the grinding is 99% most likely from bad synchros.

.

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From my understanding the GL5 oil is more slippery than the GL4. Thus not letting the tapered part of the synchro grab the gear and speed it up to make a grind free shift. I think the GL5 will cause shifting issues but I can’t be certain, I’ve always used the GL4. I have the sta lube in one toploader at the moment it’s never had an issue. 

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12 hours ago, shelbyshelby said:

From my understanding the GL5 oil is more slippery than the GL4. Thus not letting the tapered part of the synchro grab the gear and speed it up to make a grind free shift. I think the GL5 will cause shifting issues but I can’t be certain, I’ve always used the GL4. I have the sta lube in one toploader at the moment it’s never had an issue. 

From what I understand depending on how fast you are trying to shift, the GL-5 oils can be too slippery for the blocker rings work correctly.  I haven't had a chance to drive it yet with the Sta-Lube gear GL-4 oil in it.  The Sta-Lube took much more effort to pump than the Joe Gibbs Racing gear oil.  And it leaves a heavier oil film on everything.  From what I have found the Joe Gibbs gear oils are designed to run off quickly to reduce parasitic losses.  I guess that's fine for racing applications but maybe not as good for a street car that's rarely driven.

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