Transmission Autopsy

[Rob Liebbe]

Race 2 at Hallet - Transmission popped out of third gear with a loud pop/grind. Subsequently, the clutch pedal popped and then just went "limp".

Autopsy revealed seriously chewed up third gears and a broken clutch cable.

Pictures attached - hopefully.

Rebuild and upgrade in the plans before TWS in August.

[michaelmosty]

That looks like Marshall's transmission after I drove it at Cresson. :shock:

[BryanL]

Looks like a good paperweight to me.

[donovan]

Looks normal...

DD

[marshall_mosty]

T-5 transmissions just don't hold up in the long term. Apparently even at CMC power levels.

[cjlmlml]

I agree with Donovan. Looks just like mine.

[marshall_mosty]

At second glance, I think that's not an OEM transmission. It's had additonal weight savings measures taken to lower the 3rd gear weight and reduce the rotating mass... cheater!!!

8)

[AI#97]

just posing a question here but are they no parts out there in the market, even made of unobtanium, that can fix this issue with a T5? I know for T56's there are cryo'd gear sets, billet gear sets of extremely hard steel, billet main shafts and all kinds of expensive parts to lighten your wallet since these go behind Big power vipers, vettes and Eurotrash...think 1000hp cars. As long as T5's have been around in mustangs at the drag strips...there has got to be something to help you fix this weakness...? Or was the accepted alternative to go to a TKO 500/600....?

[RagingAardvark]

What are all the AI guys running for a tranny? I'm looking at a built racer 'stang and it also has a T5..it has me nervous :(

[AI#97]

What are all the AI guys running for a tranny? I'm looking at a built racer 'stang and it also has a T5..it has me nervous :(

Pushrod guys all seem to running T5's or 3550's... Modular guys are running T56's or TKO 600's I think...

[michaelmosty]

I think I am the only one running the 3550. I bought it when building my car 3 years ago and got trans, clutch, shifter, and d/s for $1K. It has been perfect ever since (w/ the exception of the 5th/reverse rail at TWS).
I have a new rail on the way along w/ a new 5th gear setup. TWS here I come. :twisted:

The trans does carry a 30 lb. weight penalty over the T5 (105 lbs. vs. 75 lbs.) but the reliability seems to be great. A big downside to the 3550 is that the 5th gear assembly is MUCH more expensive than w/ T5's. :shock:

[donovan]

I have had two third gears end up just like Rob's T-5...

The third gear is the weakest because it on the end of the main shaft and the link between the main shaft and the input shaft, the flex between the two is the problem.

There is not real fix for this, stronger gears is not the answer as they will break over time too. The key is to find a way to keep the shafts from flexing. The T5Z has done away with the roller bearings and its a tapper bearing but this has proved to be just as weak, the advatage is in the 2.95 gearing over the 3.35 in the T5.

I recently went with the A5 kit from Astro Performance hoping that the re-engineering gearset would be bulletproof... I'm still not sure if third is stripped out yet, I just got home last night.

With the recent events at Hallett with three T5, I started thinking again... I'm not giving up... I am going to fix the one I have, but I'm going to set it up a little stiff on the end play, pull the tranny after the first event and reset the play... pull it again and reset the play... and go from there.

I think the bearing are settling in and causing excessive end play.

Rob's is the only CMC T5 I have seen do this in 5 years.

************
My T-5 History

Stock 130K trany, added RR 5th gear + new bearings
After 4 events 3rd gear broke

T5Z with 15K street miles, added RR 5th gear + new bearings
After 3 events 3rd gear broke

T5, converted to A5, added RR 5th gear + new bearings
After 7 events (suspected 3rd gear broke)

I rebuilt all of these in my shop myself.
I have also rebuilt two other T5 for friends with street cars that are running fine, one has 15,000 miles on it now.

************

DD

[jeffburch]

Mine did that at TWS in '06.
Remember, the Burch-mark head gash incident?
TKO is the way to go.

jb

[Rob Liebbe]

As an information point, I have no idea what the history was on the transmission that I just broke. It came with the shell of the race car when we bought it. The car had been a race car in various forms before we got it but had been sitting in a barn for several years in a dissasembled state. The car came with two transmissions. One of them had a stock shifter and the other had a SVO type Hurst shifter. The gears seemed to shift ok while rotating the input shaft by hand on the one with the Hurst, so in the car it went, including the Hurst shifter. Three years and a couple of fluid changes later, including an hour and a half enduro and a 4 hour enduro, third gear went clunk and the clutch cable broke.


I'm going to order parts on Monday.

[Todd Covini]

Looks like a perfectly fine LAW Motorsports #9 tranny.

Kidding aside, same thing happened to me years ago.
I don't think it's chronic at CMC power levels, but it is going to happen after some wear and tear....a lot of wear and tear....like what Rob's done to his.

[chris-CMC#35]

I think I am the only one running the 3550. I bought it when building my car 3 years ago and got trans, clutch, shifter, and d/s for $1K. It has been perfect ever since (w/ the exception of the 5th/reverse rail at TWS).
I have a new rail on the way along w/ a new 5th gear setup. TWS here I come. :twisted:

The trans does carry a 30 lb. weight penalty over the T5 (105 lbs. vs. 75 lbs.) but the reliability seems to be great. A big downside to the 3550 is that the 5th gear assembly is MUCH more expensive than w/ T5's. :shock:

I have the 3550 as well; it came in the Bondurant car. I go back and forth about switching to the T5 because of weight, but have stuck with the 3550 because it's just so darn strong.

-chris

[silversvo]

my car has a 3550 in it and the previous owner tore up three t5 trannys and decided to upgrade to the 3550 and then sell the car to me. I havent had any problems with mine... I know it is heavier than the T5 as I just did a clutch in my car not long ago. I think the 3550 is the way to go...

Rob I heard you had problems at Hallett. I hope you have it up and ready for TWS in August.

[Adam Ginsberg]

Looks just like the trans I blew up back in late 2006/early 2007. However, I don't have any complaints about the T5 I destroyed - nearly 5 seasons of racing, spent a total of ~$1000 over that period of time. It equates to $200 per year for the trans.

Eventually, I may move to a 3550, if the right deal come along that includes the better 5th gear. For now, I'll have to make due with what I've got.