Mustang Transmission Options

Well, looking through the inspection covers on the TKO third gear is shredded. I'm not sure on the status of the counter shaft yet. I am planning on disassembling and inspecting the whole thing this weekend.

After a cursory search of the internet, I can get 3rd gears pretty easily. I am having a hard time finding counter shafts in stock, hopefully it's not broken - although I can't think of a situation where the gear is broken and the counter shaft isn't.

Apparently, this is a common failure mode for TKOs/3550s and there's quite a bit of speculation on what causes it. There are claims that two of the gears on the counter shaft are too close together, which they changed in the latest redesign of the box. Maybe the shafts spread too much under load reducing tooth engagement. My theory is that it's not really designed for the fully reversed loading we get in road racing. It's also possible that the stiff setup in the #50 has some affect on trans life.

I'm curious what other Mustang folks are running, and what their experience is. I'm considering switching back to a T5 (A-5 or some other variant) just because I can get them easily and carry a spare. Wrecking a transmission at COTA or Hallett and not having a spare would be a huge bummer. I can scrounge for parts to fix the TKO or send it off to a trans shop. I suppose I could get another box - but that's cost prohibitive (> $2,500).

Thoughts?
- Josh

I'm partnered with AJ Foyt Racings gearbox engineer Marty Armstrong in a little company we recently set up called Motorsport Driveline Tech. We are planning to investigate and resolve TKO reliability issues (I have them too) and offer a solution if you are interested give me a shout

So is this is a 600RR you tore up? I know Tyler has not had this very long. I thought when I purchased the 600RR I was finished having transmission issues at our power levels. I was hoping to get at least four years out of it. The A5 we were getting three years.

JJ

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Originally Posted by ShadowBolt

So is this is a 600RR you tore up? I know Tyler has not had this very long. I thought when I purchased the 600RR I was finished having transmission issues at our power levels. I was hoping to get at least four years out of it. The A5 we were getting three years.

JJ

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I'm not exactly sure what model it is. I think it's a 3550 with some work done to it. Tyler will have to verify what it is.

- Josh

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Originally Posted by Trublu

I'm partnered with AJ Foyt Racings gearbox engineer Marty Armstrong in a little company we recently set up called Motorsport Driveline Tech. We are planning to investigate and resolve TKO reliability issues (I have them too) and offer a solution if you are interested give me a shout

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Definitely interested from an engineering perspective. I'm planning on taking detailed pictures, let me know if I should do anything specifically when I take it apart that could help. I've read through the manual a few times and plan on following that.

- J

I have a TR 3650 that we rebuilt in 2013. Works like clockwork no issues. Use purple ATF for fluid.

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Originally Posted by Suck fumes

I have a TR 3650 that we rebuilt in 2013. Works like clockwork no issues. Use purple ATF for fluid.

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I was looking at those, although I think I'd have a hard time getting it to work nicely with a 5 liter. I've got one in my S197 and haven't had any issues in several years of heavy track duty.

- J

I still use the stock t-45 with no issues (knock on wood)

3550 Input/Main Shaft
10sp in, 28 out

TKO500 Cluster
Tko500/600 Case
2nd and 3rd have been replaced, not sure if it was with 3550/tko or tko500/600 parts at this point.

This happened at MSRH a few years ago, I replaced the cluster and 3rd gear, I'd probably replace the same stuff and make sure 3rd is the newer alloy.

No way I'd put a T5 in the car at this point, a 3650 can be done, gotta cut the stock bell off and make another bell work if I remember correctly.

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Originally Posted by mach1

a 3650 can be done, gotta cut the stock bell off and make another bell work if I remember correctly.

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The transmission is listed as legal in the CMC rule book but it's not clear to me if such games to make it work with a 5.0 would be considered legal??? I'd certainly get a ruling before I spent the money. I'm also not completely sure I understand the advantages, either.

I made the stock T5 in my car last for well over a decade including more than three full seasons of racing. Much of the time over 300 hp and up to 330hp/350tq for one event. That one transmission easily had around 100 events on it, half of them doing double duty with Chris Marvel sharing the car. It wasn't even a T5Z. I swapped it out when the synchros were completely worn out in all the forward gears and it crunched lightly on every shift. Other people can't make them last more than a couple of events before they blow them to pieces...


Richard P.

I bought Marshall's Astro when he parted his car out. So far so good. I also have a WC T-5 and a 12-spline clutch that will be on the trailer for out of town events just in case.

I had a freshly rebuilt (professionally) T-5 break 3rd at Cresson last year after 5 sessions on track. My theory is that the case bearing bores get out of aligment and we don't check them for alignment before assembly. Then less than adequate tooth contact and boom, broken gears.

Modifications need to fit a legal gearbox to a legal engine and make the driveline work are CMC legal...as long as not done so as to gain other advantages. For example, you're likely to need to make modifications to the trans cross member to mount a different gearbox that has the mount two inches farther rearward and that's expected and ok but if those modifications result in the transmission also moving three inches lower then not ok. Logical?

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Originally Posted by Al Fernandez

Modifications need to fit a legal gearbox to a legal engine and make the driveline work are CMC legal...as long as not done so as to gain other advantages. For example, you're likely to need to make modifications to the trans cross member to mount a different gearbox that has the mount two inches farther rearward and that's expected and ok but if those modifications result in the transmission also moving three inches lower then not ok. Logical?

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Gear ratios also have to follow the rules.

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Originally Posted by Al Fernandez

Modifications need to fit a legal gearbox to a legal engine and make the driveline work are CMC legal...as long as not done so as to gain other advantages. For example, you're likely to need to make modifications to the trans cross member to mount a different gearbox that has the mount two inches farther rearward and that's expected and ok but if those modifications result in the transmission also moving three inches lower then not ok. Logical?

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That's all logical but it's not really what we are talking about. The Tremec 3650 transmission has an integral bellhousing. That bellhousing is shaped such that you just can't drill a new bolt pattern to mate it up to a 5.0 pushrod block. To get this transmission to work on that motor, you have to replace the entire front of the transmission with a custom adapter plate that contains and locates all the bearings, shafts, shift rails, etc. in the front of the transmission. You then mount the transmission using a stock T5 bellhousing.

Making accommodations to mount a legal transmission is different than altering a legal transmission so it can be mounted. If you materially/structurally alter the transmission so you can bolt it up, is it still a legal transmission? It still mounts in the same location with legal gear ratios. I can see both sides. I'm thinking you might get different answers out of different people. I wouldn't want to risk showing up at nationals with something like that...


Richard P.

From what I can tell this 3550 doesn't have the road race 5th gear, might be a problem at COTA. To get it, I'll have to change all the gears in the box I think. I'll probably fix it at some point, but tentatively thinking of going T5 again.

- J

Stick with the Tremec 3550, 500, or 600. If you can break a TKO, for any reason, you won't make a weekend with a T5. Been there, done that. The cars T5's were designed for had 200 RWHP stock. We push 260 and put them in extreme conditions. That's sillyness and asking to break.

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Originally Posted by Sook

From what I can tell this 3550 doesn't have the road race 5th gear, might be a problem at COTA. To get it, I'll have to change all the gears in the box I think. I'll probably fix it at some point, but tentatively thinking of going T5 again.

- J

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If you stick with the 3.27's you shouldn't need the RR 5th.

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Originally Posted by mach1

If you stick with the 3.27's you shouldn't need the RR 5th.

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I had to go to fifth with 3:31's but Kevin was okay in fourth with 3:27's.

JJ

My vote would be an A-5 conversion for the T-5. Best shifting transmission I've owned. Do spend the extra few hundred bucks for the upgraded mainshaft. Facebook reminded me that I broke my stock mainshaft in my A-5 3 years ago at MSR-H... LOL

Michael drove a 3550 for 10 years before it finally literally wore out. It never "broke" and once he upgraded a few parts on the 5th gear side, it worked flawlessly. His box has a RR 5th gear and I'm sure he would sell it, but according to Joe Dietrichs it needed about $800 worth of "love" to get it back to "new-ish" condition. He's currently using a TKO-600.

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Originally Posted by mach1

If you stick with the 3.27's you shouldn't need the RR 5th.

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I had to go to fifth with 3:31's but Kevin was okay in fourth with 3:27's.

JJ

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I thought everyone used 5th on the TWS front straight? COTA's back straight is way longer than TWS front straight.

- J

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Originally Posted by marshall_mosty

My vote would be an A-5 conversion for the T-5. Best shifting transmission I've owned. Do spend the extra few hundred bucks for the upgraded mainshaft. Facebook reminded me that I broke my stock mainshaft in my A-5 3 years ago at MSR-H... LOL

Michael drove a 3550 for 10 years before it finally literally wore out. It never "broke" and once he upgraded a few parts on the 5th gear side, it worked flawlessly. His box has a RR 5th gear and I'm sure he would sell it, but according to Joe Dietrichs it needed about $800 worth of "love" to get it back to "new-ish" condition. He's currently using a TKO-600.

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Yup, I still have my 3550 just sitting at the shop. It ran "good" when I pulled it out but had a decent grind shifting from 2nd to 3rd. Everything else about it felt great. I had Joe look through it and he said to do it right it would be $700-800 to change out the worn parts and I figured after racing on it for 10-years to just spend the extra and buy a new one.
It does have the road race 5th gear which is an expensive conversion because you have to get a new main shaft and 5th gear together.
If you are interested in it give me a call and we can discuss, 972-897-1424.

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Originally Posted by Sook

I thought everyone used 5th on the TWS front straight? COTA's back straight is way longer than TWS front straight.

- J

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Nope plus at COTA you are down to second getting on the long straight. I know Kevin (at least CCW) never used fifth gear at TWS with 3:27's.

JJ

Based on measurements I took last night, the drive shafts are exactly the same for a t5 and tr3550. The input shafts are exactly the same as well. Bell housing bolt pattern is different (and I think we all knew that).

Found a T5z in spares that has an aftermarket RR 5th and appears to have been rebuilt at some point but never run. Absolutely gorgeous inside. Going to have an expert look at it to confirm. Probably going to run the T5z at Cresson while I get parts together/decide what to do for the tr3550.

Pic of A5 vs T5 attached.

- J

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Originally Posted by ShadowBolt

Nope plus at COTA you are down to second getting on the long straight. I know Kevin (at least CCW) never used fifth gear at TWS with 3:27's.

JJ

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Nope never used 5th. I was ~5900rpm at the end of the front straight at TWS and 5600-5700 rpm at the end of the back straight at COTA.