NickD

Just this past weekend I changed my transmission fluid. I used GM 88862472 I found on Amazon ( ). After I put about 80 miles on the new transmission fluid it started popping out of 5th gear. If I put it in 5th and give it any amount of gas it pops right out. Every other gear is fine. I read somewhere that this could be due to low fluid. I filled it until the fluid leaked fairly heavily back out the fill plug. I ended up putting 1 and 3/4s of the total fluid into the transmission. There's 103k on the transmission.

southal cobalt

iTrader: (3)

Yes. Probably low fluid. Except the amount you mentioned sounded correct. Check axle seals and make sure you're not losing it there.

I killed one of these f35s because I had a rear main seal leaking engine oil at the same time that I had an axle seal leak trans fluid. I did not differentiate the two because I knew I had an oil leak. Could see oil on the ground. It started out by popping out of 5th for a few weeks like you mentioned, then it locked out of every gear.

Wish I would have caught it, Because I have had 2 shops rebuild it each with problems of their own. Still don't have a perfect transmission. But oh well

NickD

I checked tonight and the fluid was completely topped up. When I removed the check plug, it started to pour out. I'll try re-adjusting the shift linkage next to make sure it's definitely getting into 5th gear.

southal cobalt

iTrader: (3)

I don't know then. If your linkage was good before. But not now, I'd suspect that it may just be an issue with your 5th synchro. You can actually access it with the trans still on the car, but I am not sure about changing it

NickD

I can't imagine an issue with 5th gear though. It's pretty much a cruising gear and doesn't get abused ever really. Maybe a few quick shifts into 5th from time-to-time. I am going to mess with the linkage today and see what happens. Maybe it's adjust where it's not perfectly in 5th and the new fluid makes it slip out more easily? I'm grasping at straws here with this but we'll see what happens.

royce777

iTrader: (29)

if you need a 5th gear and synchros I have a good set.

NickD

Okay, so I played quite a bit with the adjustments last night and there's no change. Even if I'm doing 30mph, put it in 5th and touch the gas, it pops out. Maybe it is that syncro... How do I check it and what am I actually looking for when I do see it? The last manual transmission I worked on was from a 1938 Buick Special. 3speed, syncros only in 2nd and 3rd. I was also 8 at the time.

NickD

I may have to take you up on that.

NickD

I took one last stab at the fluid level. I jacked the car as high as I safely could on one side and, using a rag, I sealed off as much of the check plug hole as I could and I filled it. I then quickly sealed it up before loosing too much fluid. I think that's about as much as I can get in there and it made absolutely no difference for 5th gear.

Over the weekend I read up some more, and learned a LOT about manual transmissions. I think this theory might be pretty accurate. The helical-cut gears, used to reduce noise, produce a thrusting motion under power. 5th gear is on it's own spline and thus has it's own set of bearings. Under load from acceleration the thrust from the gears are pushing in the direction of the syncro's dog teeth, keeping it all aligned within the sleeve. Give it throttle and we now reverse the flow of power pushing in the other direction. The worn bearings allow a slight amount of movement marginally disengaging those dog teeth and created a greater distance between the syncro ring and the cone allowing it to slip out of gear. The more gas you give it, the more forceful this will be. Thus, in the end, my syncros may be fine, my fluid may be fine, but my bearings may be shot.

I guess my next step it to pop open that 5th gear access cover and take a look for obvious, physical damage and if there's none, assume the above is correct.

Bass_Waves

iTrader: (24)

It's much cheaper to replace the trans if you don't mind having a non lsd trans. If you need a trans I got 2 of them for sale.

NickD

I'm not even sure where to start looking. Given I also track and drag race the car I'd absolutely want to stick with my LSD trans. This might be something I try and rebuild myself, I have a second car (my real hobby car) I can drive in the meantime. I think the other option I'd check out is to see if anyone offers a rebuilt unit and a core exchange.

Bass_Waves

iTrader: (24)

gotcha. If your close to NJ I can sell you a lsd trans out of my 09 lnf.

NickD

How many miles on it and how much were you thinking? I am in NJ, about 10 minutes west of R78 and R287 junction, if you're familiar with that area or ~50 minutes west of Manhattan.

Bass_Waves

iTrader: (24)

so what you telling me is your near bridge water? I'm in scotch Plains.

NickD

Ahh, yeah, you're not far at all. I'm in Lebanon, Exit 21 off R78. <30 minutes from Scotch Plains (or ~60 minutes in rush hour)

Bass_Waves

iTrader: (24)

nice. Yeah your not far. Come by if I wanna buy parts lol. I'm parting out the 09 lnf. Got mad parts to sell still. I also do a crap ton of work on cobalts. I'm sort of the go to guy for work in NJ. Somehow people know me. Guess 5 years deep gets me somewhere lol. Pm me to exchange numbers. Easier to text

ECaulk

iTrader: (6)

Just a little heads up you need some special tools for the f35, they are not like the f23 or most manual transmissions.

cobaltssdude420

I read that if there's a bit of play in the slave or throw out bearing this can happen because the clutch isn't being fully engaged with the right amount of pressure

NickD

While this sounds feasible, wouldn't this be a common problem among all gears then? I had a problem like this in an older car that would pop 3rd gear. The third gear engagement was just "sticky" and my problem there was I couldn't get it fully engaged without really mashing it into gear. If I wasn't forceful it would pop out. Though, in that case it would only pop out under WOT; normal driving it was fine. This pops out with absolutely any amount of throttle input.

T-Man

iTrader: (3)

Any time I've ever seen an issue with a transmission popping out of gear, it's rebuild time. I had it happen on my T56 in my old 2001 Camaro SS, as did my brother with his 02. Mine popped out of third gear under load.

Best of luck man

NickD

Thanks, I've conceded to the fact it needs to be replaced at this point. Thanks to Bass_Waves, I have a local source for one which I'll most likely be picking up. I guess it's time for a new clutch as well. I've been lucky with that I believe. I have the original clutch, which seems to be holding up fine with my tune and the beating I gave it. But I'll probably go with something a bit stronger just to be on the safe side.

umrdyldo

iTrader: (1)

Yep just get the GMPP Clutch, new LSJ or LNF flywheel, etc

Cobalt - HHR LNF Clutch Kit 24239996K

Add in the ARP flywheel bolts and you are good and the price isn't awful especially since you are already dropping the transmission.

Bass_Waves

iTrader: (24)

No. Don't get arp flywheel bolts. They won't clear.

NickD

I'm not certain about clutches just yet. I do actively track the car (HPDE) and occasionally on the drag strip. I have a tune to go along with a set of basic bolt-ons. The stock clutch has held up well, 103k miles, ~14 track days and 40+ drag strip runs and $65k of those miles were post-tune. So going with the stock clutch may be a perfectly viable option. I was always nervous that I was pushing it too hard though. So I wanted to consider something else stronger. I haven't started my search yet though.

NickD

Is replacing the flywheel recommended or can I just get it resurfaced? I have a machine shop nearbye-ish, I've had them do work like that before for ~$50, much cheaper than a new flywheel.