Shifting Problems - Late 5-speed GM 457 14

[DrewP]

I have two 457 14 gearboxes (late model 2.1L non-turbo, short ratio) having shifting problems.

One is the box I bought rebuild and have in my modded '85 900T. It shifts fine when cold, but when hot it is very hard to get into 5th. Feels like the linkage is binding up, or the selector is grabbing two forks at once. Even when shifting slowly the syncro usually grinds. Once it's in 5th and I've been cruising on the highway it's very stiff to get out of 5th as well. 1-2-3-4 and R remain nice and smooth. I removed the center tunnel mounted lever centering contraption when I installed it, and the shift lever is nicely aligned. It started doing it all of a sudden.

I also have the 457 14 box I took out of a friend's '94 900S convertible. It has similar situation to mine, but only in 1st. It shifts and drove perfectly in 2-3-4-5-R, but was extremely hard to get into 1st (had to use both hands) and once in 1st it wouldn't come back out without even harder pulling back on the lever and rocking the car back & forth with engine off and clutch out.



I am going to pop the covers off my new donor box with bad 1st to see what's up when I have time away from work, but has anyone seen anything like that?

I'm expecting to find either the selector finger screwed up and grabbing two shift rods at once, or the syncro spring sticking partway out of the hub and getting caught between the drive cup or something like that.

Do the sprung-ball detent grooves get screwed up and this might not be something I can easily figure out once the reverse access cover is off and the pressure is off the ball-detents?

Does that sound reasonable?

[Crazyswede]

Sounds mechanical but what are you running for oil?

[nutcase]

Maybe when you have the side cover off, put a bit of moly grease on the detent ball and see if it helps? One of Jim Mesthene's (saabcentral) tips. It'll wash off eventually but might give a clue as to the actual problem.

[Luke]

I've had problems with the syncro sleeves building burrs along the inside leading edge of the dogs that get so large that eventually it get very hard to move when the trans is hot and sometimes gets stuck in gear altogether. Some of the sleeves had a larger radius than other on the leading edge, I put a little extra radius on them with a small fine grit stone on a die grinder.

[DrewP]

The leading edge of the taper / cone surface, like the very leading edge?

I'll grab some photos when I tear into it.

Thanks for the moly grease trick on the detent ball, if I don't see anything obvious I'll try that on re-assembly too.

Mine that sticks in 5th has Redline Shockproof Ultralite or whatever the thinnest one is - it's blue, and it's always been a little crunchy when cold. I'm going to flush it out with MT90 when I have it apart, the hit on shift quality isn't worth it in my opinion.

The 190k box I got in trade that sticks in 1st I'm sure just has the old motor oil in it, the car was mediocrely serviced as far as I could tell.

[SwedeSport]

I'm currently running a 5 spd out of a 91 that had a 2.1 in my 86 project. It has always been crunchy when cold, and never wants do downshift 3-2 without a little "cant find em grind em" action. I was under the impression it had something to do with the later boxes having a POS shifting mechanism.

Im sure a big part of my issue is the synchro's.

I run 75/90 Redline in it.

[Luke]

I'm currently running a 5 spd out of a 91 that had a 2.1 in my 86 project. It has always been crunchy when cold, and never wants do downshift 3-2 without a little "cant find em grind em" action. I was under the impression it had something to do with the later boxes having a POS shifting mechanism.

Im sure a big part of my issue is the synchro's.

I run 75/90 Redline in it.

The later syncros are fussy with oil, that 75/90 is part of the problem - you want MT-90.

I'll see if I can find a pic of the area on the sleeve I am talking about - a photo would be the best way to show it.

[Luke]

ring copy.jpg (71.21 KiB) Viewed 4084 times

[DrewP]

Ahhhh... that makes sense how it would bind up.

With it taken apart can you feel it stick just engaged and disengaging them by hand? Or do you have to separate them from the shafts and actually feel for a burr that grows there and sticks down into the ID?

[turbo stephan]

I was just reading through this thread and believe that the formation of a burr might also explain my situation. Every once in a while it's hard to get it out of fifth, especially after longer highway runs when going down an off-ramp. Very recently I also noticed that after coming home from work gears are hard to engage and I almost always get a little grind when putting in reverse even after going through all other gears first and rolling back and forth a bit.

My car has 428K km, so roughly 270K miles on it. As far as I know it has the first gearbox and it was never rebuild. Unlike most of you I don't run Redline or MT-90, just normal Castrol 10W40. I think Dennis runs the Shockproof if I'm not mistaken but his car is pretty hefty modified. Is there any reason I should be running anything else?

Stephan

[Crazyswede]

is your front motor mount in good condition?

[DrewP]

Nope! It's totally shot!

The two side mounts have a bunch of card stock stuffed in the gaps (rubber barrel mounts) but haven'tt had time to pull the radiator to get to the front.

I finally brought this up because my 9-5 won't start (as of Tuesday morning) and haven't had time to figure out why.

40 mile commute in the '85 is a little hairy with 5th sticking badly

[turbo stephan]

is your front motor mount in good condition?

I think mine is OK as well but I'll check later today. I'm a bit suspicious about the left motor mount though. I have one of those sandwich plates installed at the oil filter in order to have a place to put the oil pressure- and oil temperature sensor. Whenever I need to change the filter it's very tight. I had a look at Dennis's 900 and there seems to be more space although he uses the exact same sandwich plate. I guess I'll just open the hood later and try to pull away with the handbrake on and see if there is any excessive motor movement.

Btw Drew, why bother using 5th, just take 4th. It revs a little higher but for the highway speeds in the US it should still be fine and fuel is cheap too .

[squaab99t]

My car has 428K km, so roughly 270K miles on it. As far as I know it has the first gearbox and it was never rebuild. Unlike most of you I don't run Redline or MT-90, just normal Castrol 10W40. I think Dennis runs the Shockproof if I'm not mistaken but his car is pretty hefty modified. Is there any reason I should be running anything else?

Stephan

If I were you I would be tempted to try Redline MTL, but on the other hand she ain't broke so why mess with it? At that kind of mileage it might be the same results as changing your dog's brand of food or your beer.
I do run the lightweight shockproof. (blue stuff). This last oil change I have about 75% shockproof and 25% MTL mixture. Runs great as a daily driver and shifts fine even at morning start-up. Now again Seattle is not that cold.

[Jordan]

Or you could run mt-90 and be done with it.