1948 D25 2nd gear selection issues.

[Nigel Bailey]

Hi all, seeking advice from the brains trust! I have an intermittent issue with second gear (both changing up first-second or changing down third-second) where the gear either won't engage, or will pop out). After various attempts to adjust the linkage the gearbox was pulled, disassembled and professionally rebuilt by a trusted repairer with all new internals, and a good 'old school' mechanic has had a couple of goes at adjusting the shift linkage since, but the problem still persists. First, Third and Reverse slot in perfectly. The advice I've had here in Oz is possibly too much float/end play in the second gear set, or possible misalignment between the gearbox and clutch housing-I believe there are shims for the latter? I took the car out for a drive yesterday and found that if I held onto the shifter for a few seconds after making the change that it would generally stay in second. I'm really trying to avoid pulling the 'box again and sending it back to the repairer for checking, as the logistics for this are involved, but I seem to be running out of options.  This is driving me nuts and spoiling what is otherwise a great drive-any thoughts/advice would be greatly appreciated! Thanks. 

[Sniper]

What gear box fluid are you using?  A lot of shift issues can be caused by that.

 

 

[Nigel Bailey]

Penrite Transoil T90, which is the same as the SAE 90 Gear Oil listed in my service manual. 

[9 foot box]

      This a page from a 56 Plymouth service manual. Rick D.

[Nigel Bailey]

Thanks! 

[DJK]

On 1/27/2025 at 12:06 AM, Nigel Bailey said:

Penrite Transoil T90, which is the same as the SAE 90 Gear Oil listed in my service manual. 

Be sure it is rated GL-1

[Sam Buchanan]

12 minutes ago, DJK said:

Be sure it is rated GL-1

 

Five seconds on Google:

 

https://penriteoil.com.au/products/transoil-sae-90

[Los_Control]

Just throw my 2 cents in .... The fluids available today are far superior to what was available when these vehicles were made.

They suggested GL1 back then because it is all that was available.

 

I'm using 85-140 GL5 from walmart because it is easily available to me. .... And it is cheap!

The 85 is a little thinner then the 90 .... 140 is offering higher protection and GL5 means it has more special additives to it.

The main concern is to read the label and verify the oil protects soft metals .... after a large lawsuit a couple decades ago, most if not all do .... just read the label.

 

You will get many opinions when talking about oil .... my opinion on GL1 is, I would not use it in a old farm tractor that sits in a field .... when there are better and cheaper oils available.

 

The next question would be, How are your engine mounts?

If your rubber mounts are deteriorated, shrunken and hard .... it could cause excessive play in the linkage and mess with your shifting.

[Sam Buchanan]

The issue with GL5 is in some applications (like my P15) it is too good! The superior lubricity may not allow the syncros in our vintage trannys to grip the gears sufficiently to allow smooth meshing. It was only after I replaced GL5 with Redline MTL that the syncros began functioning as designed and smooth shifting in all temps is now the norm.  I wouldn't discourage anyone from using GL1 if it works well in a particular transmission. It appears the Penrite Transoil is a modern take on GL1 and is most likely a fine option since it is intended for vintage vehicles.

[Nigel Bailey]

11 hours ago, Los_Control said:

Just throw my 2 cents in .... The fluids available today are far superior to what was available when these vehicles were made.

They suggested GL1 back then because it is all that was available.

 

I'm using 85-140 GL5 from walmart because it is easily available to me. .... And it is cheap!

The 85 is a little thinner then the 90 .... 140 is offering higher protection and GL5 means it has more special additives to it.

The main concern is to read the label and verify the oil protects soft metals .... after a large lawsuit a couple decades ago, most if not all do .... just read the label.

 

You will get many opinions when talking about oil .... my opinion on GL1 is, I would not use it in a old farm tractor that sits in a field .... when there are better and cheaper oils available.

 

The next question would be, How are your engine mounts?

If your rubber mounts are deteriorated, shrunken and hard .... it could cause excessive play in the linkage and mess with your shifting.

Thanks yes; I've belatedly remembered that the engine mounts were all renewed as part of the overhaul, as the old ones were fairly worn. Although now 'correct', there may have been some compensating adjustments done over time as the mounts deteriorated, or perhaps the alignment of the engine/clutch housing etc is not quite right? Another avenue for investigation-thanks! 

[Los_Control]

Sounds good on paper .... linkage previously adjusted to compensate for worn mounts.

New mounts, now they need to be adjusted again .... hope that is all it is.

[Nigel Bailey]

Me too!  

[Dan Hiebert]

This is sounding like an internal problem to me.  If it is affecting only one gear, it probably is not the lubricant.  The advice you've received about end play is probably pretty close, the end play for the intermediate gear set/countershaft is supposed to be negligible.  That tolerance is set with thrust washers, if they used original specs, that wouldn't account for wear and the end play would be too much. 

[Nigel Bailey]

Thanks; yes I will explore the engine/clutch housing/gearbox alignment situation, but I definitely feel it's internal, much as I'd like it to be otherwise. I've since been in touch with the specialist who rebuilt the gearbox, and the car will be going back to them in the near future for some investigation/rectification.