Quick dumb transmission question

[Sarastro]

A very simple problem.

My Bugeye has the original 948 but a rib-case transmission. The transmission shifts perfectly when it is cold, but when it gets hot, it tends to stick in first gear. Not always, but maybe 30% of the time. When it sticks, I can get it to shift, but it takes quite a tug.

I've found that if I wait a half second or so between pushing in the clutch and yanking it into second gear, it usually (but not always) moves without sticking. So, this is more of an annoyance than a serious problem. Still, I'd like to fix it.

I may have to pull the engine to deal with a clutch problem, so this might be a good time to do something about it. Can anyone suggest where to look? It seems like more than just a tight ball. I've mostly (but maybe not 100%) ruled out clutch dragging.

 

[tdskip]

Hi Steve - have ruled out any clutch MC/Slave/hose issues?

(probably, since it appears to shift OK other gears but thought I'd ask)

 

[BlueMax]

Steve,
Spridget gear boxes use brass shift forks that notorious wear. This wear will allow the gear slide assembly to over extend its design tollance and cause the detent balls to be pushing in the area inside the first gear to be where they are normally do not operate, hence the tightness. When the lubrication is cold the gear oil which should be 30 weight ND, some people use other lubercation, but 30w was factory recomendation. Anyway the thicker oil will cling tight to the slide taking up the space, hence easy shifting when cold. But when the gear oil heats up that cushion is gone and the gear will over shift due to the gear slide wear. So, while you’re replacing your gear slide it would be a good time to check 3rd and 4th too. Usually the shift rods give little trouble but would be a good time to inspect to see if you have any issues of wear. I would recommend a new first gear and changing the 3 Scyros, bearings, gaskets and rear seal. I also notice from Peter May a redesign front cover that’s utilizing a conventual’s type seal that will bring that transmission up to the 21st century technology for many miles of interrupted driving.

 

[jlaird]

BlueMax, glad you made it here. Now I have a tranny question.

Second gear is stiff to shift. Changed the tension on the springs in the slider and it made it too loose, seems like a preaty fine adjustment of some such is required. Course I been living with this as I am just tired of pulling the engine. Think I am up to 7 times now.

 

[Gundy]

Well..lookie here! Welcome aboard BlueMax!
'Bout time you started posting .
See ya soon pal!

 

[Sarastro]

At the risk of stealing back the thread, thanks to Bluemax for the informative reply. It all makes a lot of sense. The transmission is the one thing I haven't dug into so far, so now it might just be the time.

Also, welcome to the forum!

 

[BlueMax]

At this time to my knowledge first gear hub assemblies are no longer manufactured, I wish they were. Many of the 1275 ribcage transmissions have many miles on them. They are a far better transmission than the smooth case, yet still not up to today’s transmissions... Were also are dealing with bearing manufactures that are reproducing bearings that are replacing the OEM bearings. I’ve notice that some bearings are equal to OEM standards but watch out for the ones that are not up to standard. With this being said, don’t forget that the pilot bushing and the main shaft bearing are replaced with an OEM type bearing and the main shaft has no wear in this area. The spigot bearing that sits on the front of the main shaft is also needed to be replaced. All of these bearing are essential in maintaining perfect alignment for 1st gear assembly to slide properly. Jack In your situation the inner slide and first gear should not show in grove where the high side of the detent ball runs its path between first and second. Also if you can find an OEM 22G317 spring with a new OEM 22g1119 first gear provided your shift fork is perfect you should have smooth shifting from first to second. Remember that the input shaft gear mating to the main shaft is most vulnerable to flex in this area because of it being section there for assembling.

 

[bugedd]

Not to go off topic, but I need my ribcase rebuilt. Anyone out there that is recommended?

 

[Spridget64SC]

An additional consideration for 1st gear over-travel is the clearance between 1st/2nd shift fork and the inside rear of the main case casting. If one extends the first gear shift rail past the detent plunger, the detent balls can become exposed to the point they can eject, the springs can extend and lock the transmission in first gear. That is why I always shim the gap when rebuilding gearboxes. When assembling the gearbox, I'll locate the 1/2 shift fork position to the case by pressing the detent into position on the rail with a small screwdriver. Then eyeball how much shim is needed to give about 20 thou clearance. Slip the shim ring(s) over the shift rail before the 1/2 fork assembly into the gearbox. All is well and no more worry about sticking in 1st gear.

Aftermarket 22G1118 outer rings are usually available from Mini-Spares although there has been periods of unavailablity.

I'll also tighten up the 1/2 and 3/4 shift forks just a little bit in a vise if they show much wear. Squeeze them a little. Key is just a little. A little free play is needed to help with case location issues and manufacturing tolerances.

A "Second" on checking all the bearings, especially the pilot bushing. Should put in a new one anytime the engine is pulled. That is unless you are Jack and then only every 8th time . Don't forget the tail bush as well. Some of these can get pretty scored and worn out after 35+ years of use/abuse.

In our warmer southern climate, I always use 20w50 motor oil in the gearbox and in the engine.

HTH
Mike Miller

 

[jlaird]

Hmm, looks around to see who this Jack guy is.