4th to 5th grind after gear linkage work

[Targa_whaletail]

Hi,

I have an '84 Carrera 3.2 with the 915 gearbox, 120k miles, gearbox rebuild about 8k ago. It was hard to select 2nd and had a lot of play.

I just had the following replaced:

91142402404SP GEARSHIFT ROD COUPLING BUSH 911 1970-89 (PAIR) *SuperPro
SuperPro Replacement Gearshift Coupling Friction Rings / Polyurethane Suspension Bushes will give you:

91137504300 ENGINE MOUNT 911 65 -89 NOT CLUBSPORT OR CABRIO
Mounts for both engine and gearbox

PCG42402000 GEARSHIFT ROD REPAIR KIT
Repair Kit contains:
- 91142402404 x1 Shift rod coupling
- 91142413901 x1 Ball socket
- 91424222400 x1 Friction ring
- 90142422900 x2 Conical screw

I also had the Seine gateshift kit installed.

New Swepco 201 gearbox oil.

Standard (not short) shifter.

My questions:

1. At highway speed, I'm getting a grind 4th to 5th. Any idea what is wrong? Is this nicking reverse, or maybe needs more adjustment on shifter linkage or what? Mechanic thinks this is due to the change of gear oil...

2. The leather boot / gear gaiter is in poor condition. What part works to cover the Seine gateshift? I see Lakewell have a leather part, but they only advertise from '85 on.

Overall, other than the 4th to 5th issue, massive improvement. 2nd still needs some care - allowing synchros to do their work...

Thanks!

[Discseven]

May be called wrong on this but seems a stretch to blame gear oil. Typical grind would be dogs not sync'd due to worn rings... Given comprehensive rebuild, surly all things internal were attended as needed. Mechanic would have aligned shift linkage and tested. Interested to see where this goes... in particular if anyone supports oil theory.

[porschenut]

Your shift linkage needs adjustment. I had exactly the same issue on one of my previous cars. It's a DIY job, outlined in the 101 Projects book.

[Targa_whaletail]

Originally Posted by Discseven

May be called wrong on this but seems a stretch to blame gear oil. Typical grind would be dogs not sync'd due to worn rings... Given comprehensive rebuild, surly all things internal were attended as needed. Mechanic would have aligned shift linkage and tested. Interested to see where this goes... in particular if anyone supports oil theory.

Well, the gearbox rebuild was by the previous owner, and I had the extra items changed above just now as these seemed to have been untouched...

The mechanic actually thought it was the synchros, but that the new oil mightn't be working great.

I guess since it's a 4th to 5th issue, it's not due to nicking reverse / reverse lockout pawl..?

Car is going back in anyhow, as I'd have thought (hoping!) that it is a further shift adjustment needed...

I'm assuming the worn / torn leather boot / gaiter is not at fault. Also assuming I have replaced all of the linkage parts that could be at fault. Just for clarity, 4th to 5th was fine before this. Just awkward getting into 2nd (still not wonderful, but maybe a 915 "feature"), and a heck of a lot of play (and concern at wrong gear selection as things were so vague).

[Targa_whaletail]

Originally Posted by porschenut

Your shift linkage needs adjustment. I had exactly the same issue on one of my previous cars. It's a DIY job, outlined in the 101 Projects book.

Thanks - just saw this - was writing reply above!

Is this the book you mean? https://books.google.ie/books?id=onrWx9_kJmQC&pg=PA106&source=gbs_toc_r&cad=3#v=onepage&q&f=false

[Discseven]

Am not familiar with Seine kit. Does that modify stock config?

[Targa_whaletail]

Originally Posted by Discseven

Am not familiar with Seine kit. Does that modify stock config?

It is a spring loaded gate for 1st and 2nd that fits on top of the shifter assembly - Seine Systems > Gate Shift Kit

[DRACO A5OG]

You just need to adjust the coupler one more time. Does it still jam when you double clutch?.

item #2, yes the leather boot will fit nicely over the shift kit mods, I have the Siennes kit, with the rubber boot and leather boot on top of it.

[cabmandone]

Had basically the same problem when I installed my Seine gate. IIRC you need to make sure when adjusting the shift coupler that the shift lever is in the 1/2 plane. I used a quick grip to hold it there. Once I had it close, I loosened up the coupler and made very... very slight adjustments. It could be both a slight fore/aft and a clockwise/ counterclockwise adjustment. When the engine is off, can you go through the gears smoothly?

[Targa_whaletail]

Originally Posted by DRACO A5OG

You just need to adjust the coupler one more time. Does it still jam when you double clutch?.

item #2, yes the leather boot will fit nicely over the shift kit mods, I have the Siennes kit, with the rubber boot and leather boot on top of it.

I didn't try to double clutch - just had this twice on the motorway [sometimes double clutch when changing down at low speed]. Shifted 4th -5th Eeek! Shifted back to 4th, no drama, shifted back to 5th Eeek!. Was around 50mph ish I think. Tried shifting up to 5th later when doing around 35mph and all seemed OK.

In terms of a replacement rubber boot, then leather boot / gaiter over the top, what do you think of:
In terms of the boot, for the rubber part, is this OK? Part 91142418101
Buy Porsche gearshift boot parts | Design 911 (Porsche brand / original) 911 1970-89 Gearshift Rubber Boot - Type911 - Porsche Parts Shop

The leather boot could be:
https://www.lakewell.com/en/porsche/911/84-89/shift-boot-/-gaiter-porsche-911-85-89
or
Porscheshop
or another brand?

From what I can tell, the rubber boot was the factory one as can't find a Porsche number for the leather boot..? This is a UK Targa sport (not supersport) so I've no idea if the leather boot was part of the sport pack - it's not something that is properly written up that I can find.

Originally Posted by cabmando

Had basically the same problem when I installed my Seine gate. IIRC you need to make sure when adjusting the shift coupler that the shift lever is in the 1/2 plane. I used a quick grip to hold it there. Once I had it close, I loosened up the coupler and made very... very slight adjustments. It could be both a slight fore/aft and a clockwise/ counterclockwise adjustment. When the engine is off, can you go through the gears smoothly?

Makes sense - thanks. I'll pass this on to the mechanic. Simple adjustment beats (another) gearbox refresh!

Actually, it's done less than 4k miles since the rebuild. Service records indicate that after 400 miles, "3rd gear was lost" - suspected manufacturing fault as cog for third gear was badly damaged with teeth rounded off on right side. Was re-rebuilt then. Handwritten note "that gear change now a bit clumsy, but hopefully will ease with wear". Personally, I think the sloppiness noted was primarily due to the coupling.

By the way, Sherwood (Seine Systems) said something similar via email just now in terms of the adjustment.

When shifting with engine off, it is a little tight. 5th hardish to get. Reverse very hard (but that's good!).

[DRACO A5OG]

I purchased the leather boot from our host to replace my torn leather before I even put the Sienes gate shift kit. Very nice quality and thicker to boot. If you have the center console, just make sure you give enough slack on the leather so it will not bind when you shift. I installed mine snug and tight and it resulted in leather squeel against the plastic console.

[VFR750]

I just did an adjustment and it is very tricky to get right.

Get some white paint and a fine paint brush. Mark the location of the spline to the coupler.

You can then accurately make changes and know if you really did or not.

I noticed that you could put the spline where you think you want it, and the act of tightening the pinch bolt moves the coupling, and it is no longer where you think it was.

Took a couple tries to get right and it was night and day.

One! Spline tooth pitch changed from balky 3-2 downshift to butter smooth.

Also the depth of the spline into the coupler really matters relative to the region where the reverse lockout is and the internal workings of the transmission gate. Takes a while to find the right spot where the transmission internal gate is in line with the 3-4 to 5-R mid point.

The paint line really helps.

[Walt Fricke]

The 4th to 5th grind makes little sense (not that it isn't happening). When you adjust the coupler in the back you want the boot or boots off the shift tower so you can see how things are working. It is easy to be off a bit in the fore and aft direction so that when you go into 5th the pawl (reverse blocker) doesn't clear the shift lever shaft. Then when pulling out of 5th to go to some other gear, if you pull a bit too far to the rear on the shift lever you knick reverse. Worse things can happen, as reverse has no synchros or sliders to damage - you just round the edges of the gear teeth a bit. But it isn't good, and certainly is worth an eek or two, as you feel stupid.

Basically, the shift lever is a bit too far rearward in this situation.

When you move, against the stock spring pressure, the shift lever all the way over to the right (to get either 5th or Reverse), an arm sticking out to the side of the shift rod which sticks out of the transmission (and to which the rear of the coupler attaches with that grub screw)drops into a slot milled into the top of a fore and aft rod, to which the fork which moves one way to get 5th (which has the usual synchros and slider teeth) engaged. Move it the other way, and it slides a gear onto the idler gear between the input shaft gear and the gear on the pinion shaft, with the idler doing the reversing of the rotation. All five forward gear are "constant mesh" gears, but reverse actually has a toothed straight cut gear moving to mesh with the idler - something like that, anyway.

It is hard to see how the act of lowering this arm into the slot on a shaft, and moving the operating sleeve to the rear so it can engage 5th is going to cause reverse to knick the idler.

But after a rebuild you'd not expect an issue with the 5th synchronization system, and 5th is the least likely system to get worn out - unlike 3d, where there is a temptation to hurry the 2-3 upshift.

Still, I'd experiment with the fore and aft adjustment, unless dry shifting to 5th lets the pawl click nicely into place so in order to get to reverse you have to go to neutral, let the lever move to the 3/4 plane, and then push to the right and back.

The Seine is one of the two great improvements which transform the 915's shifting. The other is a shift coupler with no slop at all in the bushings. Not quite up to Boxster and later shifter standards, but PDC.

[Targa_whaletail]

Originally Posted by DRACO A5OG

I purchased the leather boot from our host to replace my torn leather before I even put the Sienes gate shift kit. Very nice quality and thicker to boot. If you have the center console, just make sure you give enough slack on the leather so it will not bind when you shift. I installed mine snug and tight and it resulted in leather squeel against the plastic console.

Thanks - that's good to know - had just seen a brown gaiter on first search here.

Is there any advantage to putting the Porsche rubber boot under the leather boot, or just a new leather boot (slack as you suggest) and maybe put something on the Seine upstand?

Originally Posted by VFR750

I just did an adjustment and it is very tricky to get right.

Get some white paint and a fine paint brush. Mark the location of the spline to the coupler.

You can then accurately make changes and know if you really did or not.

I noticed that you could put the spline where you think you want it, and the act of tightening the pinch bolt moves the coupling, and it is no longer where you think it was.

Took a couple tries to get right and it was night and day.

One! Spline tooth pitch changed from balky 3-2 downshift to butter smooth.

Also the depth of the spline into the coupler really matters relative to the region where the reverse lockout is and the internal workings of the transmission gate. Takes a while to find the right spot where the transmission internal gate is in line with the 3-4 to 5-R mid point.

The paint line really helps.

Thanks - I will pass this on.

Originally Posted by Walt Fricke

The 4th to 5th grind makes little sense (not that it isn't happening). When you adjust the coupler in the back you want the boot or boots off the shift tower so you can see how things are working. It is easy to be off a bit in the fore and aft direction so that when you go into 5th the pawl (reverse blocker) doesn't clear the shift lever shaft. Then when pulling out of 5th to go to some other gear, if you pull a bit too far to the rear on the shift lever you knick reverse. Worse things can happen, as reverse has no synchros or sliders to damage - you just round the edges of the gear teeth a bit. But it isn't good, and certainly is worth an eek or two, as you feel stupid.

Basically, the shift lever is a bit too far rearward in this situation.

When you move, against the stock spring pressure, the shift lever all the way over to the right (to get either 5th or Reverse), an arm sticking out to the side of the shift rod which sticks out of the transmission (and to which the rear of the coupler attaches with that grub screw)drops into a slot milled into the top of a fore and aft rod, to which the fork which moves one way to get 5th (which has the usual synchros and slider teeth) engaged. Move it the other way, and it slides a gear onto the idler gear between the input shaft gear and the gear on the pinion shaft, with the idler doing the reversing of the rotation. All five forward gear are "constant mesh" gears, but reverse actually has a toothed straight cut gear moving to mesh with the idler - something like that, anyway.

It is hard to see how the act of lowering this arm into the slot on a shaft, and moving the operating sleeve to the rear so it can engage 5th is going to cause reverse to knick the idler.

But after a rebuild you'd not expect an issue with the 5th synchronization system, and 5th is the least likely system to get worn out - unlike 3d, where there is a temptation to hurry the 2-3 upshift.

Still, I'd experiment with the fore and aft adjustment, unless dry shifting to 5th lets the pawl click nicely into place so in order to get to reverse you have to go to neutral, let the lever move to the 3/4 plane, and then push to the right and back.

The Seine is one of the two great improvements which transform the 915's shifting. The other is a shift coupler with no slop at all in the bushings. Not quite up to Boxster and later shifter standards, but PDC.

Thanks - I will pass this on. Agreed, it's a little surprising on the upshift.

I deliberately went for the Polyurethane shift coupling bushes rather than a fixed coupler like the Wevo PSJ as I had read this was not great for street use due to gear whine, vibration etc. transfer that would otherwise be damped by the bushing. Not sure if this is correct..? I also avoided the short shift kit to be kind to the synchros, and used Porsche original rather than solid gearbox/engine mounts.

[DRACO A5OG]

The rubber boot is to keep dust and debris out of there. Also helps reduce noise. I guess the leather can do the same as some if not many have removed the leather and center console. Even the rubber boot if they track it.

[Targa_whaletail]

Well, would you believe that I continued to drive the car and have had no recurrence of the 4th to 5th grind. No adjustments made. Maybe I was just adapting to all of the gearbox changes (user error!), or indeed the box was bedding in after gear oil change?

[DRACO A5OG]

Well it is possible. Just keep and eye on it and practice double clutch just to be safe or rev match at a minimum.

[Targa_whaletail]

Originally Posted by DRACO A5OG

Well it is possible. Just keep and eye on it and practice double clutch just to be safe or rev match at a minimum.

Fingers crossed... I do double clutch down to first if still moving anyhow.

A new leather boot and a Porsche rubber boot are on order to tidy that up.