Jump to content
Trnelson

Transmission experts please help

Recommended Posts

So I have a grind downshifting to 2nd. My first thought is I need to replace the synchros, yet even when double clutching I still get the grind. I can drive around casually just fine but the least bit of aggression creates a grind. Thinking that when the first road salt goes down I’m gonna drop the transmission and see what is going on.  Could the gear be screwed up?  My question is, where is the best place to shop for parts for a Type A transmission?  Plan to do a complete clutch rebuild and rear main seal while I’m in there, I just want to get the best parts so I only have to do this once. 
Thanks for the help

Share this post


Link to post
Share on other sites

First make sure your clutch hydraulics are working well and your clutch friction material is still good before you blame the transmission.

Just went through this with a friend. 2nd and reverse were hard to get. Trans was just fine when I took it apart. Clutch was worn out as were the hydraulics.

Share this post


Link to post
Share on other sites

The right fluid can add thousands of miles to a worn transmission.  Redline, Synchromesh, etc.  Plain old Valvoline 80-90W isn't good enough.

Share this post


Link to post
Share on other sites

I just received AC Delco synchromesh friction modified oil, plan to change tomorrow if all goes well. Can the fluid or friction plate really make that much difference for only one gear?  All other shifts are smooth as silk. It took a few attempts but I’ve wrestled most of the monkey motion out of the shifter and it feels great other than the 2nd gear downshift grind. It did have the grind prior to my fix on the monkey motion. 

Share this post


Link to post
Share on other sites

Clutch issues show up more in reverse because it has no synchronizer.  So, if reverse is fine, then worn clutch is less likely.

You can have one worn synchro and fluid will make the difference.  But, your problem seems odd in that you say it happens when downshifting.  I assume it's fine while upshifting?  And why are you being aggressive in downshifting?  You do mean the shift from 3rd down to 2nd, right?

3rd gear is usually the first synchro to wear out also.

If the fluid change doesn't work and you decide to take the transmission out, save the fluid,  It won't be ruined from just a few miles in a worn transmission.  It will be fine to use after a rebuild.

Share this post


Link to post
Share on other sites

Aggressive like when your coming into a curve and downshift from 3rd to 2nd. Pretty bad grind in that situation. 1st to 2nd is smooth unless I’m really pushing it (I’ve only had it happen once or twice). I live in the mountains so lots of opportunity for hard or aggressive downshifts coming into corners.  Hopefully the oil will make a difference, if it were worn synchros I think double clutching would hide that issue but not 100% sure. Good info on the oil, I’ll save it as long as there are no shavings on the plug when I drain it. Could the clutch pedal need to be adjusted, friction point is a little over half way up. 
thanks for the pointers

Share this post


Link to post
Share on other sites
8 hours ago, Trnelson said:

Aggressive like when your coming into a curve and downshift from 3rd to 2nd. Pretty bad grind in that situation. 1st to 2nd is smooth unless I’m really pushing it (I’ve only had it happen once or twice).

I've got exactly the same in my 240z (with a worn out euro 5 speedbox  the FS5C71B which i got out of a euro 240z)    Or when coming from 4 or 5 th braking hard and going to second gear... it's very  much a grinder..!!!    My gearbox started that years ago and now going back to 3th from 4-5th is also starting to grind.  It needs a new set of bearings AND synchro's. (after 49 years!!!)

Btw, what do you mean with a " A type transmission" ?   an FS4W71A? 

Maybe @Zed Head knows where we can get a revision set for these transmissions.

Share this post


Link to post
Share on other sites

It certainly sounds like your synchros are wearing down. Probably below minimum spec. A good oil could make all the difference. The GM AC delco oil suitable for brass synchros has yielded good results for some members here on this forum. That or Redline MT-90 75W90 GL-4 gearoil.

Btw: The A type transmission (F4W71A) uses the same synchro rings in second gear as the F4W71B the FS5W71B and the early FS5W71C transmissions (the 71C without the reverse synchro). All four gear have the same synchros. Only fifth is little smaller in diameter.

 

  • Like 2

Share this post


Link to post
Share on other sites

Gentlemen, thank you for the advice. I changed to the AC Delco this morning and within A 15 mile test drive I can tell an enormous difference!  I would agree that the synchros are probably somewhat worn add that to a poor gear oil choice and it equaled a bad grind.  I feel like I’m good for now but I’ll probably dive into the transmission over the winter. 
I read somewhere that the earlier transmissions had “Porsche” type synchros?  Is that not the case?

  • Like 3

Share this post


Link to post
Share on other sites
57 minutes ago, Trnelson said:

I read somewhere that the earlier transmissions had “Porsche” type synchros?  Is that not the case?

The transmission with the porsche type servo synchros are the 5 speed usded in the roasters (short tale) and the 240Z outside the US and Canada.

They have the code FS5C71A and later the FS5C71B. The "C" refers to the type of synchro ring. W is for Warner type ring.

Of course there are some exceptions along the way with both syncrhos in the 5 speed transmission. Then you can find the warner synchros in 1st to 4th gear and the servo type in 5th.

Share this post


Link to post
Share on other sites
Gentlemen, thank you for the advice. I changed to the AC Delco this morning and within A 15 mile test drive I can tell an enormous difference!  I would agree that the synchros are probably somewhat worn add that to a poor gear oil choice and it equaled a bad grind.  I feel like I’m good for now but I’ll probably dive into the transmission over the winter. 

I read somewhere that the earlier transmissions had “Porsche” type synchros?  Is that not the case?

Glad to hear you got it sorted! That’s very pleasing indeed!

Share this post


Link to post
Share on other sites
13 hours ago, AK260 said:

I changed to the AC Delco this morning

And ofcourse this oil is no where to be found in Europe.. the Netherlands to be specific?  Is it General Motors ac delco 75W90 or ??

i see 10-4016 75w90 is a pure synthetic and an other one which i forgot.. i went to amazon.nl (netherlands, typed in: ac delco 75w90 and..... i got a Bosch filter... yep.. thats amazon in the Netherlands....pffff... never have and prob. never buy from amazon overhere. duhhh..:finger:

Share this post


Link to post
Share on other sites
3 hours ago, dutchzcarguy said:

And ofcourse this oil is no where to be found in Europe.. the Netherlands to be specific?  Is it General Motors ac delco 75W90 or ??

i see 10-4016 75w90 is a pure synthetic and an other one which i forgot.. i went to amazon.nl (netherlands, typed in: ac delco 75w90 and..... i got a Bosch filter... yep.. thats amazon in the Netherlands....pffff... never have and prob. never buy from amazon overhere. duhhh..:finger:

I recommend SWEPCO 201 for use in Servo (Porsche patent) synchro 'boxes. The proper Porsche specialists in NL should be able to supply it, but here's a UK-based supplier:

https://type911shop.co.uk/epages/de867ca1-377e-432e-84fd-bdccf2206766.sf/en_GB/?ObjectPath=/Shops/de867ca1-377e-432e-84fd-bdccf2206766/Products/2042

Share this post


Link to post
Share on other sites

8 hours ago, dutchzcarguy said:

And ofcourse this oil is no where to be found in Europe.. the Netherlands to be specific?  Is it General Motors ac delco 75W90 or ??

i see 10-4016 75w90 is a pure synthetic and an other one which i forgot.. i went to amazon.nl (netherlands, typed in: ac delco 75w90 and..... i got a Bosch filter... yep.. thats amazon in the Netherlands....pffff... never have and prob. never buy from amazon overhere. duhhh..:finger:

 

4D7A63CB-FC5A-469C-ACEC-6441F077663D.png

Share this post


Link to post
Share on other sites

Apparently Pennzoil developed the "synchromesh" formulation for GM.  So if you can find Pennzoil Synchromesh, it's the same formulation, as the internet seems to show.

But, for whatever reason, maybe because a copyright wasn't acquired or not enforced or because GM let the formulation data out, there is a "synchromesh" for several other brands of oil.  And a "Synchromax".

https://www.amsoil.com/search/?text=synchromesh&timezoneOffset=420

https://www.valvoline.com/our-products/grease-gear-oil/synchromesh-mtf

https://www.pennzoil.com/en_us/products/other-oils-fluids-fuel/manual-transmission-fluids-axle-oils/synchromesh-manual-transmission-fluid.html

https://www.royalpurple.com/product/synchromax-manual-transmission-fluid/

 

Share this post


Link to post
Share on other sites

And, on the Porsche synchros, there are several discussions about steel baulk rings in the early 5 speed Nissan transmissions.  Another side thread.

JMortensen said he used to work for a shop that used Swepco 201 for those in the Porsche transmissions, and a blend of Swepco and ATF for the "brass" Nissan rings.  I used the blend on an old 5 speed ZX transmission that had problems with Redline and it fixed it.  It's spendy but good stuff.  Most Porsche racing shops will have a 50 gallon drum of it in the shop.  That's where I got mine.

https://www.classiczcars.com/forums/topic/19361-gearbox-oils/

https://www.classiczcars.com/forums/topic/19261-early-5-speed/

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.