T-5 lost 5th today during test drive...Thoughts?

[BillZ260]

Dr, you are right I should do it right and buy the shaft, but I don't want to spend any more $$ right now IF I can aviod it. If I could go back, there are lot's of things I'd change, but what this project is about is learning. Of course, I just learned that I need a better solution, and I am still deciding not to go with it.....so I'm just dumb! Well maybe not dumb, more like cheap and stubborn. I am possitive there is a viable solution that will work for me w/ what I have. What that is, remains to be seen. If I fail twice then i'll try something else because the first time, I didn't know any better.

 

I'll pull this thing, inspect the C clip and the shaft for wear like Terry mentioned, may look for a heavier C clips to install in the groove, maybe out of some other material, dunno what's out there and see what happens.

 

Terry, the shaft was shaped, drilled, groved whatever else BEFORE it was hardened. So any change in form after hardening changes stress in the shaft and would weaken it. I am assuming the material was hardened but I'm almost positive it is. This is why I can't simply cut another groove behind the first one and make my own G-force style set up. It would probably snap clean in two.

[BillZ260]

A bit more plan of action. Smalley Steel Ring Company ONLY makes retaining rings. I'm going to put together some data from this situation and see what they recomend. I'm betting there is something better than a simple C ring, will see...

 

http://www.smalley.com/retaining_rings/about_retaining_rings.asp

[BillZ260]

Got the tranny pulled this afternoon, that was a work out. I'll pull it apart this week and see what's going on in there, here is a little more detail about the pull http://forums.hybridz.org/showthread.php?p=849398#post849398

 

Terry, do you agree that drilling the hardened shaft would weaken it?

[blueovalz]

I'm not totally convinced of this, BUT, I'm not a subject matter expert in this subject (much less ANY subject). I know there are members who do know the answer to this and somehow we need to get this question out to them.

[BillZ260]

Weather was nice today, so I took a half day and pulled the trans apart. I'm pretty sure I used the wrong retaining ring. I did email Smalley, to see if they have any other thoughts on this, but based on Kevin's statement, the smaller ring should work.

 

Took some measurements and pictures to document.

Shaft OD is 1.160

Groove OD is 1.090 and is .125 wide

 

Comparing the dimensions of the rings below and the measurments above, it's fairly obvious to me NOW that the smaller rings is a more appropriate fit in the groove.

 

This is the Snap Ring installed to retain the driven OD gear, note the marks (Luckily the Snap Ring is softer than the shaft)

 

THIS Snap Ring was sitting in the groove of the rearward most groove, note similar but less prominent marks. I think this snap ring should be holding the driven OD gear.

 

This is the groove the retaining ring sit in. Look at the 4th and 5th splines from the TOP. Looks like shadows but those are the only slight wear marks produced by the failure. They are slightly polished looking and I don't think the material really deformed any.

 

This is the groove the smaller ring was sitting in. It's just behind the speedo driver gear. I'm not really sure what it holds, but it caused enough confusion.

[Evan Purple240zt]

I have been watching your progress! Your a brave man, I hate transmissions LOL.

 

Looking good, nice detective work.

 

I have nothing productive to add, just a pat on the back!

 

Evan

[blueovalz]

This is the groove the retaining ring sit in. Look at the 4th and 5th splines from the TOP. Looks like shadows but those are the only slight wear marks produced by the failure. They are slightly polished looking and I don't think the material really deformed any.

 

These photos are great. So...are you saying the right edge of this groove is NOT rounded/ramped as a result of the snap ring slipping out? In particular, the upper most spline in this photo looks like trouble. To me it looks ramped, like this → |___/

[BillZ260]

Thanks for the kind words Evan, I didn't like transmissions before I hosed my self on a V6 T5 and figured what the heck! Pulled it apart and followed the manual, it's easy cheasy!

 

Terry, I just double checked, there is maybe one spline that has the slightest edge taken off the very corner, it's MAYBE .005 taken off. The ramp you are looking at there is the bit of Trans Fluid in tension across the two surfaces Thanks for freaking me out.

 

I'm glad I took time to document this, hope it helps someone else in the future. Still more to come, waiting to hear from Smally and Kevin.

 

Does anyone think they can calculate the amount of load/pressure that little snap ring is seeing. Smalley had that on their request for quote.

[blueovalz]

Something I found out a while back is the installation of these rings is as important as the size. Using a ring that has an initial tight fit may be for not if it is spread beyond its yield strength upon intallation in the attempt to get it over the splines. I thought I'd find a clip one size smaller for a better grip, only to find out that it had to be stretched beyond its yield strength in order to get it over the shaft. As a result, once installed, it has less grip than the larger ring had in the first place. My lesson; spread it only far enough to slip it over the shaft, and no more.

[BillZ260]

That's a really good point. It's completely possible that I simply over stretched it durring instalation. I've asked Kevin if he can supply dim's on a new ring, and we'll see what Smalley says as well.

[dr_hunt]

Man what a complicated calculation. I'll take a stab at it, and in no way should you assume that I'm correct. Assuming you can get 400lb ft to that driven gear, the coeffcient of dynamic friction between the gears is unknown probably negligible, the angle of gear cut is unknown, but the resulting component force is three fold. One force is going to try to separate the two shafts perpindicular to the shaft axis, one is going to try to force the 5th gear rearward on it's shaft and the remainder is transferred to the output shaft.

 

Just a guess, but with a 30 degree gear angle your going to get approximately 60 to 70 lb-ft force acting rearward on the gear. With straight cut gears that goes to zero.

[blueovalz]

Dr,

 

From what I can observe looking at my gears (this is a guess), the OEM 5th gear set has a 40º to 45º degree cut (yea, that's a lot). The 5th gear design is intended for quiet, highway oriented operation in which the powerplant RPM is well below the peak torque. Install a high ratio differential (mine is 4.11), added torque, especially down low, and you start having problems.

 

Perhaps you can answer this concern I also have about the OEM gear ratio or design, and that is the really tiny (relatively speaking) driven gear diameter. I'm wondering if this plays into the separation forces, or losses between the two gears as well. It would seem to me the smaller the gear diameter, the more lateral force imparted in the gear-shaft. Is this true or insignificant?

 

All of this is why I threw in the towel and purchased the G-force 5th gear-set last week. This set has a much straighter cut on the gears. When I talked to their engineer, he said the gear will whine somewhat because of this design, but said as long as you've also got the gear cluster plate installed, separation of the gears will be reduced and that it will no longer be the "weak" gear for those using this gear as intended (road or track events). It is a .75 ratio, which is at least better than my current .80 ratio (70 MPH drops from 3000 to 2800 RPM). He also reiterated that they alway build their cases with preload on the bearings to allow for the expansion of the aluminum case (more so than the steel shafts and gears) as opposed to the several thousanths of clearance set by the manufacturer (his words). Listening to him talk about this gave me the impression that this was almost as important as purchasing all the nice tough gears.

[BillZ260]

Dr, thanks for the guestimate! I'll relay that figure and see what they say.

 

Terry, I get your point above on G-force unit, sounds like it adds several advantages over the stock unit. I don't plan on road racing often, and if I do I'll just have to stay out of 5th.

 

My car is primarily going to be street driven, and yesterday I played with some numbers based on my current tire size. They may be off some but the attachment shows my Engine RPM in 1000 RPM increments and the relative drive shaft speed, wheel speed and car speed for those RPM levels.

 

I seriously doubt the Areo Capabilitys of my Z alowign me to safely go much past 120, so I should be ok through 4th on any speed runs. I'll religate 5th to cruising to work and road trips

 

I'd also like to thank you guy's again for your input on this. I don't want you to feel like I'm ignoring your input. I'm simply deciding that heavy duty 5th (1-4 are tought as nails so far) isn't what I need right now, what I need is to finish up the car and start enjoying it

 

Stay tuned for snap ring decisions and updates.

ZSpeedEst.txt

[dr_hunt]

I may be wrong, but when you drop the clutch in 5th gear, that shock load would be significantly higher. IMO I don't really see a better fix than going with the straight cut gear set. OR you can have the groove machined like __ at the back which helps clip retention. Any qualified machinist could do that for you for about $50 IMO.

[jgkurz]

I have a G-Force T-5 built by Kevin and I had him do every upgrade possible including the HD 5th gear. I like the transmission and it's held up with no issues. The only things to be aware of is it's picky about what fluid is used. Too heavy and gear shifting will be notchy, too light of fluid may not properly lubricate. I use a combination of G-Force fluid and Royal Purple Synchromax.

 

The other thing is gear noise. 3rd gear downshifts are LOUD if you are at just the right speed. 5th gear definitely has an audible whine that might be annoying to some, especially over a long trip. For us L28 guys it's really the strongest manual transmission available that doesn't take massive fabrication to install. If you don't apply full power to 5th and use it just for cruising I would highly recommend you keep the OEM gear.

 

The whole reason I went down the G-Force path is because I shredded 5th gear in my Datsun 5spd (non-T5) on a WOT blast down the freeway.

[BillZ260]

Smalley doesn't offer anything that "heavy", so they are out. I did find one other snap ring that would be the snug fit that I'm lookign for but isn't just available to buy online. Looking some more, this Grainger PN 5CE45 could also work but is a different style.

 

Kevin kindly measured one at his shop and it measured .086 wide x 1.144 ID and .125 thick all the way around, this ID is only .006 smaller than the one that failed, that spooks me. I ran the #'s based on Kevins measurments.If my measurments are right, these two scenarios are how the current design is holding the driven 5th in place, which I am having a hard time swallowing...

 

Again, the Shaft OD is 1.160.

and the groove OD is 1.090

 

1 - the snap ring is perfectly centered on the driven gear. It has (1.160 - 1.144/2) .023 all the way around the ring holding the 100ish lbs of thrust against it.

 

2 - more likely, gravity or centrifical force has set the ring completely on one side, giving you the full .035 of the groove depth contact on ONE side and about .016 on the other.

 

It just seems to me that the resting snap ring ID should be the same or smaller than the groove in the shaft to obtain the maximum area to spread that thrust across.

 

Am I nuts?

[blueovalz]

I don't think you're nuts. What I would do though is get a couple of the bigger rings, and a couple of smaller rings just to experiment with. I would take one of the smaller rings and install it, then remove it, and THEN measure the ID. if it is larger than when you put it on (by a reasonable amount???), then it's been stretched in the process of installing it (and ruined in my opinion), and you may want to return to a larger ID clip. From the looks of your photos, it appears the larger ID OEM clip is not stretched (based upon the spacing of the gap). IF the measurement is the same after installing and removal of the tighter clip, then you know you've not ruined the spring tension in the ring, and you're good to go.

[blueovalz]

I got the HD 5th speed gearset today and thought I'd throw out some photos of the OEM as compared to the G-Force set. The HD gear ratio will be .75 while the OEM set was .59 (and my original ones which I had to destroy in order to disassemble the gearbox was .80). To say these are stouter that the OEM gears is an understatement!

 

 

[Gollum]

He also reiterated that they alway build their cases with preload on the bearings to allow for the expansion of the aluminum case (more so than the steel shafts and gears) as opposed to the several thousanths of clearance set by the manufacturer (his words). Listening to him talk about this gave me the impression that this was almost as important as purchasing all the nice tough gears.

 

I'm loving this thead, and learning plenty, so I'm just gonna shut up and keep reading after this post.

 

I was researching the Gforce T-5 gearset a while back, and found several instances posted online in which people blew their transmission even with the Gforce gears. In all of the cases (unless the information wasn't there) they were using the OEM case and had the gears put in by a local shop, NOT somebody with in depth knowledge and racing experience with the T5.

 

The case is a serious weak point in the T5, which is why Gforce sells an aftermarket case that's stronger. Just thought I'd mention all this for those that might think that improving gear strenth is everything.

 

 

Regarding the 5th gear clip though... why isn't there a clip that could somehow be "locked" so it can't come apart and is kept held tight against the grove? Would that not matter and it'd still be pushed off? It just seems like if you controlled the expansion of the clip that it'd be less likely to come off. Seems risky, but tac weld it maybe?

[blueovalz]

I've also read some feedback about failed gears as well. I could not ascertain whether the case split, or the gears failed, so I asked the engineer to comment on that. His experience with building over a 1000 cases was that yes, the case will split, but not before something inside the case gives out first (again, his words). He has seen his gears break at some pretty high power levels, and the resultant damage then forces the gears apart, which then splits the case.

 

His response about the blogs are "you'll find good and bad feedback out there, but I can only go by what I see come through the shop. I rebuild a case for this one guy every 100 or so passes who is running a 3300lb Mustang in the high 9's using a stock case with our gears. He uses a diaphragm clutch, is a skilled driver that is easy on the gears, and has a near perfect set-up...so you run the numbers...he's never had a failure yet".

 

Being this (the BlueOvalZ) is a light car, decent but not excessive (is there such a thing?) horsepower, and with some shifting care, I should be fine. If not, lesson learned to pass onto those who need it.

 

In regards to the set-up: The OEM specs are .002" clearance on the cluster gear. G-force takes the total clearance with no shims (~.110", but should be measured for an actual clearance), and then adds .008" to the actual number for the total shim thickness. This then places the preload on the bearing with a -.008" clearance. Once the case warms to 180º or so, that clearance becomes close to .000" due to the expansion of the aluminum case. He recalled one day when he set the input shaft preload to roughly the same amount, set the case out in the sun to warm up, and an hour later could go out there and free-spin the input shaft as if it had no preload at all.