The Getrag F23 Tutorial - By Emc209i (Page 26/28)
Will OCT 24, 07:34 AM

quote
Originally posted by pmbrunelle:

It is hard to select a “rating” as such, it depends on the life desired in each gear. Typically, tests will not only be conducted at maximum torque; some failures might be uncovered more with high cycles of lower torque.

Here is an interesting article about the smoothness of engine torque:
http://www.epi-eng.com/pist...m_piston_engines.htm

I was wondering how I could have broken my Muncie with my V6 while the Muncie seems to have a good reputation on this forum. V8s are popular and seem to hold up with Fiero transmissions, but the torque delivery is smoother with more cylinders.

So apparently a “torque rating” would depend on the number of cylinders.

Also, the evening before my Muncie broke, I was having a bunch of misfires. I don’t know if misfires actually disrupts the rhythm and increases the peak torque at some point in the rotation.

I may need to superimpose the single-cylinder torque curves and see what happens with a V6 with a misfire, like how they did on the website.



No try it with a Harley!

Yes, that's why V12's are renowned for their smoothness. Also, torque from firing a cylinder falls off quickly as the crank continues to turn. The closer the firing interval in degrees, the less torque from the prior cylinder falls off before the next cylinder fires and the smoother the engine is.



quote
Originally posted by pmbrunelle:
What does it mean when we say “stiffness-driven” design for NVH? Does this mean that misaligned gears are more noisy than gears which remain correctly positioned with respect to one another? So the case and shafts are designed with a max misalignment target?

Load capacity of gears that are well-aligned is better than for crooked gears. So this is perhaps a happy side-effect for the hot-rodder?



Assemblies are designed for high enough stiffness to keep resonant frequencies away from excitation frequencies to result in quieter operation. Yes, a happy side effect is that the extremely stiff assemblies are also extremely strong. That's why so many modern engines can handle >30psi of boost... at least for a while.

[This message has been edited by Will (edited 10-24-2024).]

hunter29 OCT 25, 09:18 PM
Thanks guys, yes a serious question as i'm planning a swap..

Much appreciated...
Trinten OCT 25, 11:04 PM
Hi Hunter,

I can tell you that I, and others, have definitely put some pressure on the F23. Jncomutt has done repeated clutch dumps, I've pushed mine on the quarter mile track. It's a solid transmission.

Best advice? If you rebuilt it, or have a shop do it, definitely make sure they 'shim' the shafts correctly. There was a few TSBs on this transmissions, and I understand one of them was around shims to deal with noise, and if you "over-shim" it, it stresses the bearing and the bearing goes boom. Outside of that, I think the only F23s that have died are in cases where the axle snapped and swung around, cracking the case apart.

In a race situation, 1st gear is useless. In daily driving, 1st gear is only marginally useful... but still a great transmission. If I could tolerate having a manual again, it would be in my current build.
Will OCT 26, 08:17 AM

quote
Originally posted by Trinten:

Jncomutt has done repeated clutch dumps, I've pushed mine on the quarter mile track. It's a solid transmission.

Outside of that, I think the only F23s that have died are in cases where the axle snapped and swung around, cracking the case apart.



Didn't one of the turbo 3800 users break the left bearing boss off his diff carrier?

Also, it uses the stock Fiero manual transmission inner CV joints. I've broken one of those with a 282.
pmbrunelle OCT 26, 10:05 AM

quote
Originally posted by Will:
Assemblies are designed for high enough stiffness to keep resonant frequencies away from excitation frequencies to result in quieter operation.



I work on smaller parts (not entire engine or trans); usually the OEM gives a vibration spectrum (intensity, frequency), and then our component is expected to remain intact/functional after being exposed to said vibration. So this is more typically about durability/breakage.

For the smaller parts, there are no vibration-related requirements about the parts resonating and becoming noise radiators.

I expect more pickiness about noise as (quiet) electric takes over. In the powersports world, the engine is loud enough to mask a lot of unwanted noises.

[This message has been edited by pmbrunelle (edited 10-26-2024).]

pmbrunelle OCT 26, 10:09 AM

quote
Originally posted by Will:
Didn't one of the turbo 3800 users break the left bearing boss off his diff carrier?



I saw a stripped something in a facebook group recently in a Getrag F23, not sure if it was a final drive pinion.
fieroguru OCT 26, 10:18 AM

quote
Originally posted by Will:
Didn't one of the turbo 3800 users break the left bearing boss off his diff carrier?



Yes. Justin had a couple of failures:

Justin had an output shaft bearing failure:

quote
Originally posted by Justinbart:












He also had a differential carrier housing failure:


quote
Originally posted by Justinbart:

Broke the Differential.






Took a video of how loose the diff was before I pulled it off and seen how broken it was




A testament to the case strength of the F23 is neither of these broke the case.
hunter29 OCT 26, 10:43 AM

quote
Originally posted by Trinten:

Hi Hunter,

I can tell you that I, and others, have definitely put some pressure on the F23. Jncomutt has done repeated clutch dumps, I've pushed mine on the quarter mile track. It's a solid transmission.

Best advice? If you rebuilt it, or have a shop do it, definitely make sure they 'shim' the shafts correctly. There was a few TSBs on this transmissions, and I understand one of them was around shims to deal with noise, and if you "over-shim" it, it stresses the bearing and the bearing goes boom. Outside of that, I think the only F23s that have died are in cases where the axle snapped and swung around, cracking the case apart.

In a race situation, 1st gear is useless. In daily driving, 1st gear is only marginally useful... but still a great transmission. If I could tolerate having a manual again, it would be in my current build.



Thanks.....
pmbrunelle NOV 14, 10:15 PM
For information, Roger Thelin now sells a front transaxle bracket that is meant for the GM Metric transaxle.

https://thelinsells.limited...bracket-number-three

Here it is on my 2000 Sunfire 2.2 OHV transmission:


Some tweaking may be needed to fit it in place.
fierofool NOV 16, 10:24 AM
I don't want to hijack this thread, but would any viewers happen to have a good clutch release fork for an 86 or 87 Getrag? PM or email me if you do.