G50 Occasionally Struggles to Go Into Reverse When Cold
 

Been having this problem more and more, and it seems totally random but only happens when the engine is stone cold and when the car hasn't been driven in a week or so.

I just can't get the car to go into reverse. I move the selector into the Reverse plane but when I push forward it won't engage and I hear kind of a thunk. Sometimes it won't go into ANY gear at that point but if I keep working it it'll eventually go into a gear. If I then let the clutch out to move the car forward slightly and then try reverse again it'll go.

From that point on I don't usually have any more issues.

I'm thinking this winter I'm gonna have to drop the engine and take a peek at this thing.

Thoughts?

My G50 improved dramatically after rebuilding the shift mechanism in the tunnel. Pelican sells the kit to do this. JWST-G50-BUSH $36.

Gear oil weight and brand?

had the same issue some years ago, there was 80W-90 in the gearbox, changed to SWEPCO 202 MolyXP 75w90 Synthetic Gear Lube (not the 201, that's for the 915 gearbox) and now can do whatever I want with the gearbox, at whatever temperature

Hi John, I'm using Liqui Moly 75W-90 Fully Synthetic Gear Oil.

Was told at a recent rally by a pcar mechanic that I should be using Mobil 1 Delvac 75W-90. So I'm planning on changing to that this weekend.

I put Mobil 1 Delvac 75-90 in my G50 and it shifted much smoother especially the first few shifts in the winter.

I would start by checking engine / transmission mounts and the shift linkage.

My thoughts as well.

Unless the car is due for an oil change, don’t just start changing oils. I’d also look to the clutch slave and that fluid over the gearbox fluid itself.

I changed the shift bushings in the front last summer, and while the shifter is tighter and now has almost no slop, it doesn't prevent this issue.

I'll take a peek at the engine/gearbox mounts but I'm sure they're fine.

I'll pop the cover off and take a peek at the coupler, too. Haven't been in there for years so that's certainly a possibility.

I have bled the slave cylinder in the past when doing a brake fluid flush but this hasn't improved the situation. Both Master and Slave cylinders are 11 years old.

Gearbox oil has about 8,000 miles on it, so while it's not at the end of its life I'm inclined to change it nonetheless.

Have you played with the alignment of the shifter to the body? Did you mark the position of the shifter fitting before loosening the 3 bolts? This would've been when you disassembled to do your shifter bushings. Did you use the 5mm pin to index the shifter while re-installing it?

Any alignment issues with 5th or other gears, or is it just R?

Because you're able to roll the car some and get it to go, it sound like alignment with the shifter mechanism. Would like to know more about mileage and what work occurred before you started noticing this.

Some items to check; Sounds like some are complete.

1) Fluid/Bleed
2) Shifter condition
3) Shifter position/alignment (relative to body) <--- Feels like you are here. Interested to know if you followed the book on re-installing your shifter.
4) Shift coupler condition
5) Master/Slave
6) Pedal stop position
7) Trans/Engine mount sagging/wear/broken
8) Trans/Engine position/alignment (relative to body)
9) Trans internals

I did indeed mark the shifter fitting before loosening the 3 bolts, and did indeed set the gap at 5mm when reinstalling.

I think the very first time I noticed this issue was driving out to Rennsport Reunion in 2018, and I just changed the front bushings last year.

I have had this happen occasionally for 1st gear, too, Like reverse, if I can get another gear and let the clutch out to move the car forward slightly I can then get first to engage.

In the 11 years I've owned this car I've not had the engine or gearbox out. I'm thinking that might have to change this winter unless I can find something obvious outside of the gearbox.

Didn't see your mileage yet. My G50 is at 150k. I couldn't solve the cold shift issue (mine occurs on 1st gear, sometimes R) and tore into internals. I found my 1st gear synchro worn. R was pretty beat too.

You sound exactly where I was before tearing into trans. Hopefully you find something else.

I have a thread going for my partial g-50 rebuild. I'm due for a thread bump.

Mileage on the gearbox is 166k. I have no service record showing it was ever apart so I'm probably in the same boat as you.

I had been following your thread, concerned I may very soon be up against something like this myself.

If you're handy and can get a few pullers the 1, 2, 5, and R synchros are not bad.

Good luck OP, you're always welcome to drop a PM to ask questions or discuss the work more if you go that path.