Transmission Carnage Thread

[VerusEric]

As most of you high horsepower guys know, there are issues with keeping the transmissions together at north of 250-300wtq. There are multiple people working on fixes, Velox Motorsports included. We're trying to keep costs down by replacing just what is breaking and testing is going well thus far.



I wanted to start a carnage thread to attempt and put all the photos and stories in one spot. Hopefully if all goes well, this will benefit the whole community. I'll start out with (3) bad transmissions I have torn apart, of the (5) total units I have taken apart for rebuilds/inspection.

Starting out with #1. This transmission completely shredded 4th gear. No other significant damage took place. It appears the material/heat treat/tooth profile was not made for this amount of horsepower (~450rwhp). This trans would need a new output shaft and 4th gear, along with anything else it ruined by ingesting teeth. May as well buy a new transmission at this point.





#2: This transmission came to me with losing shifting into 2-3-4-6. 4th gear retaining clip broke somehow, still working on why but we think we have an idea. Once 4th gear retainer broke, 4th gear began to slide down reverse gear and ultimately the shift selector/clutch moved too far and lost the balls/springs that need to be in the clutch to work properly. Demise was quick and did not give any hints it was going to break. To rebuild this unit you'd need a new counter shaft and labor (~$450 + labor).





#3: This transmission came to me for our upgrade. It didn't actually break but had started to chip reverse gear's teeth ever so slightly. Customer did not want to wait for a new counter-shaft so he is going to see what happens with our straight cut gears. Install went smoothly and everything seems fine, we shall see.





Looking forward to seeing other carnage pictures! If at all possible, give some decent background to what happened, how it happened, fast or slow demise, the setup it's on, and some pictures.

Update, #4 trans:
2nd gear shredded, no shift issues appeared, no other major damage noted. 40k miles turbo'd at 300+wtq, 55k miles total. Car was tracked, drifted, and autocrossed, so it had been through a lot and broke on a *soft* 2nd gear pull getting on the highway.







#5 Trans:
I tore apart another local's transmission on Friday night. 380-420 whp, driving fine then one day 4th was lost. Below is the carnage, which isn't terrible, but will require a countershaft for repair as well as a few other parts.





Thanks,
Eric

[humfrz]

Interesting topic. Good photography!

So, you got any pictures (or theories) about a "whining" transmission ... ??


humfrz

[cdrazic93]

@Reaper

[Ultramaroon]

It just looks like the shafts aren't holding up to axial load at those retaining clips/shims.

[Matt@Cosworth]

re-grinding those square wire / sharp edge circlip grooves with a large round wire circlip would reduce stress
typically an easy fix to handle more power is make the gears wider if you can

[hmong337]

subbed

[GsxrMe]

Are these Transmissions going to shit from hard shifts or the HP/TQ? I shift fast but I don't throw the pig into gear like I won't see it tomorrow.

Are aftermarket fluids advertised as better causing more harm than good?

[VerusEric]

Originally Posted by humfrz

Interesting topic. Good photography!

So, you got any pictures (or theories) about a "whining" transmission ... ??

humfrz

A lot of people have commented about this. I honestly have no idea other than the gear profile OEM chose and that the transmission is closer to the driver than in other applications.

Originally Posted by cdrazic93

@Reaper

Transmission #1 is Nick's. He sent it in to us to try and come up with a potential fix. That was about a half a year ago. Hopefully he posts up with some other carnage pictures!

Originally Posted by Ultramaroon

It just looks like the shafts aren't holding up to axial load at those retaining clips/shims.

I am starting to think that as well. Originally I was thinking the clips were not strong enough so we machined up some retaining clips. Then I got a hold of transmission #3 and my mind changed rather quickly. What would happen though if we took off the axial/thrust load from the helical gears ?

Originally Posted by GsxrMe

Are these Transmissions going to shit from hard shifts or the HP/TQ? I shift fast but I don't throw the pig into gear like I won't see it tomorrow.

Are aftermarket fluids advertised as better causing more harm than good?

It's from the hp/tq. 250-300 is not much these days, but you have to remember this is *double* OEM, which is pretty impressive in my opinion.

Aftermarket fluids are not causing the gears to break. Fluids could cause issues with shifting potentially but not gears breaking.




To me, it seems like there are two distinct issues at this moderate power level.
1) The heat treat/gear profile/material used by OEM is not strong enough for this amount of torque. 3rd and 4th are the weakest gears in the transmission and these are letting loose first as a result.
2) The counter shaft's reverse gear cannot withstand the thrust (axial) load that the helical gears put on them.

3) There may be an underlying issue as well, which may be the synchros. The odd thing is there are those of us that absolutely love this transmission and have nothing but good things to say about how it shifts, then there are others that absolutely have nothing but bad things to say about it.
-I have a few theories on what is happening here as well but nothing concrete.

Would love to see more photos and hear some more stories! I know I can't be the only one tearing these apart.

[humfrz]

Originally Posted by VeloxEric

.....................The odd thing is there are those of us that absolutely love this transmission and have nothing but good things to say about how it shifts, then there are others that absolutely have nothing but bad things to say about it.

-I have a few theories on what is happening here as well but nothing concrete.

.........

I have a theory too, simply stated ...... "in many cases, some people know how to shift a manual transmission .... and some people don't" .......


humfrz

[Ultramaroon]

Originally Posted by VeloxEric

I am starting to think that as well. Originally I was thinking the clips were not strong enough so we machined up some retaining clips. Then I got a hold of transmission #3 and my mind changed rather quickly.

I don't remember having nearly as much backlash on any of my previous RWD cars. There's a shit ton of slop in my diff but it's dead quiet so I let it go.

It might be a material or treatment issue. Maybe local temper to trade some hardness for a tougher area right at that those mating surfaces?

Originally Posted by VeloxEric

What would happen though if we took off the axial/thrust load from the helical gears ?

You'd sacrifice the customers that daily this thing because straight cut gears howl like lonely wolves.

[FRS Justin]

Originally Posted by humfrz

I have a theory too, simply stated ...... "in many cases, some people know how to shift a manual transmission .... and some people don't" .......


humfrz

I have over 600hp at the wheel 521 tq and still on my stock trans. I don't flat foot shift it just speed shift. IMO its the sudden shock that is killing this trans. Don't get me wrong its not a strong trans, but slamming gears at max power is a death sentence to it.

[Hawk77FT]

How about shot peening and isotropic treatment? Planning to that to mine in the near future!
I am doing that now to my 4.556 crown and pinion for le diff

Sent from my HTC_0P6B using Tapatalk

[FRS Justin]

Originally Posted by Hawk77FT

How about shot peening and isotropic treatment? Planning to that to mine in the near future!
I am doing that now to my 4.556 crown and pinion for le diff

Sent from my HTC_0P6B using Tapatalk

IMO hardening a gear will make it brittle it needs to be able to absorb a shock. IMO more surface area is needed in tooth contact area

[Hawk77FT]

Originally Posted by FRS Justin

IMO hardening a gear will make it brittle it needs to be able to absorb a shock. IMO more surface area is needed in tooth contact area

If shot peening doesn't make the gear absorb the shock better I don't know what will:
http://machinedesign.com/metals/shot...ases-gear-life
If anything, it would reduce the surface subject to cracks or brittle.

On the other hand, I get what you're saying by the increase of the contact area. Why not both?