mark kibort

so you are saying that my problem is probably the dogteeth synchros on each of the gear sets that interlock when engaged? the geares have no ridges or raised areas , so it must be something that is surrounding the gears, correct? I dont know much about these things except how to put one in now, and hot to remove the top cover and make that spring thingie fly off when i pull the cover off.

mark kibort

after living w this "Pop out " problem for a year now, its really getting old, when you want to put both hands on the sterring wheel in slow turns and feather the throttle and it pops out without being held. ugggg. however, i mentioned that there is NO issue under decel or even moderate acceleration which i thought migh point to greg browns comment on how the gears mesh with ridges at the edge of the gears to keep them in gear. are we all sure there is not something else that keeps the mechanisim in gear besides the gears themselves, like a detent position in some of the mechanical slider/lever parts?

if there was something i could modifiy by pulling the top cover that would be great.

anyone anyone??

I dont want to pull another transmission to fix this issue!! AHHHHH!

Thanks

Mark

Lizard928

sure, throw a rubber band in there MK.

Let us know how it works for you!

BC

mark kibort

Hey, knuckle head, just seeing if we missed something or if there is something topical that can break, bent or be misaligned to keep the gears engaged. I guess I could puts around the holbert transmission and see if there is anything that sticks out as obvious.

FredR

Mark,

My experience with [motorcycle straight cut] gearboxes is that they jump out of gear when something is worn. Had this problem on my first Brit motorcycle when I was young and stupid [now old and stupid]- jumped out of first gear- usually just when I did not want it to and nothing I could do to keep it in- even though I tried to hold the gear lever with my foot. Turned out the dogs on the layshaft were [badly] worn- a noted weak point for those in the know about that box [as it later turned out]. One s/h layshaft later- problem solved. Doubtless the 928 gearbox is much much more complicated but same principal I would think. So, my money with Doc Brown on this one.

No guarantees but if you want to fix it you are going to have to pull it and strip it I rather suspect and "the longer you leave it the more it will cost to fix it" and I', sure Doc B will attest to that one!

Hoping you find a quick/cheap solution though-

Best wishes

Fred

mark kibort

Thanks Fred, however, it has NO issue when any kind of power or decel is applied. in otherwords, if im slightly accelerating in 2nd (bad gear right now), its just as hard to pull it out of gear as it would be in a good gear, say 3rd.
also, because this happened in just one lap of a race, im wondering if there could possibly be something else . you would have thougth that the poping out of the gear, might have happened at some point before hand, intermittently and it didnt.
If the transmission has to come out, it will. but, its not really a problem unless i just have my hand on the transmission during no load driving. so it hasnt got worse at all in several races since this first started happening.

again, ill have to see what the holbert gear box looks like in this area.


also, do you guys think its worth repairing the holbert gear box. as you might remembre, i spun some gears . 5th and 4th are pretty chewed up. others look ok. if the synchros are still good and all the other stuff but the actual gears for 5th and one other,, what will that cost to fix?
almost just worth finding a used gear box again, if that can be done.

Dr brown have any of those new S4 tranmsissions left??

Thanks,

Mk

GregBBRD

Only ever had '85/'86 transmissions. Still Borg Warner design, but different.

Yes, still have a couple. Haven't been in a huge hurry to sell them. Frankly, could not think of a better investment for a few dollars to sit in....this stuff is going to be worth its weight in silver.

Not really clear about your problem. If it only happened once during an entire race....isn't it possible that you simply did not have it engaged completely in gear?

If it was a one time incident...forget it, until it happens again....more often.

There are springs and detents on the slider/hub. However, these only keep the slider in the center of the hub when the transmission is in neutral.

And there are springs and detents on the shift shafts....but these are primarily "interlocking" pieces to keep one from engaging multiple gears are the same time.

The only thing that keeps the transmission engaged, in any specific gear, are the "negative" cuts on the gear teeth and the slider. These have a "negative angle" machined into them, so that they interlock when engaged. This is the reason why it is so difficult to "pull" the transmission out of gear, when there is load applied (in any gear).

Any external linkage problem that keeps the transmission from shifting completely into gear can cause your problem.

Any broken/loose engine or transmission mount that would allow excessive movement of the assembly could cause this problem.

Anything that gets bent (shift forks, shift rods, etc.) could cause a transmission to "jump" out of gear.

If the bolts that hold the pinion bearing into the transmission case were to come loose, the transmission could "pop" out of gear (although this would become terminal in a very short period of time.)

If the large nut that holds the "gear stack" onto the pinion shaft came loose, the transmission could pop out of gear (again, for a very short period of time....before this became terminal.)

If a syncro had damage...it could feasibly stop the hub and the gear from being fully engaged.....however, this would be an extremely rare event.

I'm not sure of the "vintage" of the "Holbert" box. If an early Borg Warner (like my '85/'86 transmissions) some of the pieces will interchange, into a later style gearbox.

I would not throw it away.....

mark kibort

Hi Greg and the others interested.

The gear box problem is a CLEAR popping out of gear when no load is on the transmission. (either accelerating or decelerating is not an issue at all)
In otherwords, if im just between pushing the gas and brake, it will pop out of gear. does it all the time, without fail. so, I have to race with one hand to hold it in gear during the 2nd gear turns where I really need two. (as soon as I apply the gas, I can let go and its fine before the 3rd gear shift.

im thinking the dog teeth tapers are fine, because it happened all of the sudden and its only in 2nd gear that this happens.

I took the liberty to take the cover off the holbert transmission and do some cadaver work. I found that with the cover off, nothing keeps the gear engaged. a slight finger pressure and it comes out of gear. as soon as the cover is put on, there is a substantial pressure to keep the gear engaged.. Put that side mounted " long spring" and then the engagement of the gear is rock solid, even more than just the cover alone.

I think this is the problem. that long spring fits on a little nipple on a lever mounted on the cover I can imagine that spring falling out, or off the nipple and that might be the issue. what does that lever spring and that roller do to put pressure on that long slide shaft? tighen the entire assembly up so its less clunky?

I have a feeling between the cover and the remote mounted spring, the problem will be found. I hope it isn't in the cover (what is that spring thing mounted to the cover?? reverse lock out? anyway, if that is what it is, I have to cut the chassis to get to the top cover of the transmission. (as Anderson had done, by cutting and then replacing the removed steel chassis area, with an aluminum plate with screws or rivets.

Thoughts?

Mk

GregBBRD

Unless it is a linkage problem, actually keeping the transmission from fully engaging a gear, you might as well start setting out the tools you need to remove the transmission, if you are serious about fixing it.

Rob Edwards

Mark, judging by the amount of work involved in creating and riveting the panel back in, I'd venture you'd be ahead if you'd just suck it up and pull the transmission. There's nothing you can do through that access panel anyway.

GregBBRD

I'd venture that Mark cut that hole in his race car, went over to another vehicle and cut another section out that was 1" bigger, all the way around.

So easy, when you have multiple chassis to cut up.

Mrmerlin

yep and cutting a hole in the unibody will weaken it and provide not much more access,
result times wasted that could have been spent wrenchin on dropping the transaxle

mark kibort

Greg, Thanks.
Uggggg..... yes, I cut the hole. the hole looks good, but the cover i will be attaching to cover it, may not be.
You guys are right, should have just sent the old holbert transmission out to GB or somewhere for a 5th gear replacement. it was a great gear box, all synchos working well, no issues, but 5th gear stripping out and the gear on the bottom of it. dont think there is much more damage, but thats the next move. get that repaired, or repair the newer one in the car now.

I did remove the cover. all parts are working fine, but expanded the springs a little to make more resistance, but I think what made the most difference ,was getting the boot over the linkage outside the gear box. im thinking , its forward pressure was trying to push 2nd gear , out of gear for a year of racing, and maybe that forced a weird wear pattern on the 2nd gear or its associated slider, synchro, etc.

anyway, got a big hole, put it all back together and drove it. well, its not near as bad, but any vibration , bump on the road going around a 2nd gear turn in equalibrium, and it can pop out of gear. before it was guarantee, now its random. I thnk being in a hurry to get the transmssion in, and leaving that top boot bunched up, was want caused the problem, but thats a guess.

anyway, making a cover out of some sheet aluminum from the old holbert car door and trying to form it to look at least close to the hole shape and size.
If its structural, i will use rivets to re-attach. if not, ill just use some sheet metal screws. Thoughts?

Thanks for the help and advice. after the next few races, ill pull the darn thing.



mk

mark kibort

yep, makes sense now. I guess I was wishing for a simple fix, expecially since the gear box works so well in all other areas???

so, what does a rebuild like this cost ?

what does a rebuild replacing a 5th gear on the holbert transmission cost, providing its only the 5th gear and then the gear below it that it meshes with?

thanks

Mark