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06-23-2016, 04:01 PM | #1 |
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Tranny experts - ATF in 39 trans ??
I know that some of the todays modern transmissions call for ATF in them .
After telling an "old timer" of my downshifting problems (grinding going from 3rd to 2nd) in my recently rebuilt tranny , he suggested using ATF in it . I had never heard of this before . He says it won't hurt it , just might leak a little .Is this a common practice ? For the record , I have tried 90wt. & 140wt. , and it made no difference . Thoughts ? |
06-23-2016, 04:04 PM | #2 |
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Re: Tranny experts - ATF in 39 trans ??
I suspect something other than a problem with the transmission gear lube. A properly built and functioning 39 transmission should not have this problem on a down shift, assuming that your are attempting the down shift at an acceptable speed or RPM range. My '39 transmission does not have this problem.
A call to Mac VanPelt may help you further trouble shoot the problem. |
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06-23-2016, 04:04 PM | #3 |
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Re: Tranny experts - ATF in 39 trans ??
I think it will leak a LOT!!
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06-23-2016, 04:23 PM | #4 | |
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Re: Tranny experts - ATF in 39 trans ??
Quote:
Bruce
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06-23-2016, 04:46 PM | #5 |
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Re: Tranny experts - ATF in 39 trans ??
Some of the new synchros sold are not up to par. Assuming that the clutch is adjusted correctly, I'd guess the synchros were either not replaced, or were the poorly made type.
PS....do not use ATF trans fluid in that transmission. Regular gear oil (GL4 spec in a 140 wt)
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06-23-2016, 04:58 PM | #6 | |
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Re: Tranny experts - ATF in 39 trans ??
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Thanks for all the reply's so far , guys ! |
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06-23-2016, 05:15 PM | #7 |
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Re: Tranny experts - ATF in 39 trans ??
My mechanic told me that the only reason ATF is used in a modern tranny is to help with gas mileage, not your issue.
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06-23-2016, 05:34 PM | #8 |
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Re: Tranny experts - ATF in 39 trans ??
If you ever open up a trany that uses ATF you may figure out why they use it. Modern gearboxes are an art form in their complexity. They have a way lot more parts in them than the old buggers have. Some of the newer materials that are used require a whole different kind of lubricant to keep things working correctly. The oil being thinner doesn't always help all that much for windage when they are shifted to direct drive or overdrive.
Mac knows where he speaks on blockers. His early Ford transmission rebuild book illustrates how to check the new ones during reassembly. The external conical shape of the gear has to mate well with the conical shape of the blocker ring to be effective at equalizing rpms. I learned to drive in an old 1952 F3 with the non synchro 4-speed. Besides double clutching, a person gets good at knowing just how much to increase the engine RPM to match the oncoming downshift dogs. In a partially synchronized 3-speed, there should be no trouble selecting the lower intermediate gear from the high one. The blocker is not working as it should if it does have a grind. Low gear isn't synchronized so a little grind going in is not unusual there. |
06-23-2016, 05:51 PM | #9 |
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Re: Tranny experts - ATF in 39 trans ??
Off the top of my head I'd say it would leak like a sieve. The modern transmissions that do use that type of fluid (oil) have much better advances in sealing than our old transmissions.
Mart. |
06-23-2016, 06:04 PM | #10 | |
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Re: Tranny experts - ATF in 39 trans ??
Quote:
the 39 sedan i drove I would downshift at 40-45 in hills, it was the 60 with the early type syncros,but couldn't just force it ----the 46 with the later syncro I would downshift at any speed even at 50---just jam it in gear and slide my foot off the clutch as I floored it---that trans was made of all used parts, still worked fine when i sold the car |
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06-23-2016, 07:22 PM | #11 | |
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Re: Tranny experts - ATF in 39 trans ??
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I believe it is time to take it to" Charlie NY ". He is less than 2 hr. away . |
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06-23-2016, 07:38 PM | #12 |
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Re: Tranny experts - ATF in 39 trans ??
we raced an HQ holden in the series here for a few years,using atf in the gearbox was worth some small bits of HP,and you needed all the HP you could get,,I looked inside the box after three years and it was like new.
Lawrie Last edited by Lawrie; 06-23-2016 at 07:44 PM. |
06-24-2016, 10:54 AM | #13 |
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Re: Tranny experts - ATF in 39 trans ??
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06-24-2016, 12:31 PM | #14 |
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Re: Tranny experts - ATF in 39 trans ??
Modern transmissions use carbon-fiber laminate synchros that must have ATF instead of gear oil.
As for the OP, sounds like you may need some new synchros in that trans. |
06-24-2016, 12:59 PM | #15 |
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Re: Tranny experts - ATF in 39 trans ??
Yep, they changed the lubrication requirements when they went to the carbon-fiber synchros.
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06-24-2016, 01:43 PM | #16 |
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Re: Tranny experts - ATF in 39 trans ??
Use a can of STP in it, it will be the smoothest shifting transmission you;ll own.
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06-24-2016, 02:05 PM | #17 |
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Re: Tranny experts - ATF in 39 trans ??
I think there is/was something called "Double Clutching"?
Seriously, have Charlie look at it . |
06-24-2016, 02:33 PM | #18 |
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Re: Tranny experts - ATF in 39 trans ??
Yes, there still is "double clutching". Unfortunately, it does NOT fix worn-out synchronizers.........it only allows you to shift in spite of worn-out synchros. DD
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06-25-2016, 09:13 AM | #19 |
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Re: Tranny experts - ATF in 39 trans ??
You may also want to investigate top-quality synthetic transmission oils of the proper viscosity (GL4 spec in a 140 wt). This stuff is incredibly slippery, so if any lubricant is going to help resolve your problem, synthetic is your best bet.
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06-25-2016, 10:15 AM | #20 |
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Re: Tranny experts - ATF in 39 trans ??
I don't believe there is a lubricant that will fix my trans . I do believe there is something wrong mechanically w/ my trans . Probably syncro related .
I was just throwing the ATF thing out there 'cause I never heard of it being used in old trannys . Thanks to all who replied ! - FF |
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