Official Tremec 3650 Issues Thread

Be careful when requesting a new trans

From what I understand when Ford (or GM) replaces your transmission you will get a factory rebuilt unit which might have its own set of problems down the road.

The transmission in my 01 Mustang is pathetic but I'm reluctant to have them replace/repair it until I know what the real problem is - I'll try to wait until the warranty is about to expire.

When cold I granny shift or double clutch until its warmed up - and here in Canada that is for six months of the year.

Ford says the gringing/bumping is normal but for what - a tractor trailer.

I'm embarrassed when the car is cold and the shifting is so difficult that I'm being passed by minivans and other sXXXboxes - that's a far cry from the muscle car image the Mustang is suppose to portray.

I'm hoping Ford will come forward with a fix like they did with the Mustang Cobra but I doubt they will.

Ford will only respond when they get negative publicity from car owners and the media which impacts future sales.

I hope that the subscribers of this and other forums can make a difference.

timbo3282 said:

I LOVE the car, but I am looking at replacing the Trans with a T-56.. I haven't heard of any cars having shifting issues with that tranny... anyone else having issues with their T-45?

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I don't think that's a good swap. Think about what happens when you put in a T56. The T56 has a much steeper first gear ratio, and you'll have to put in 4.10:1 rear-end gears just to get the same overall first-gear ratio as stock 3.27:1 gears with a 3650 would yield.

At the same time, the 6th gear in the T56 has a numerically higher ratio than 5th on the T3650. So you will rev even more than a 3650 would with 4.10s, while getting the same overall torque multiplication as a 3650 with 3.27s, and shifting three times in the quarter-mile instead of two. Oh, the T56 is heavier, robs more power through parasitic loss, and costs at least twice as much.

Am I the only one who thinks this swap is just dumb? That was a rhetorical question. I know most of you would give your left nut to have a T56.

Yeah I just got a 2001 GT w/ 26,000 miles.

seems to have 1-2 grind.

2002 GT 38,000 Have not had the 1-2 shift prob yet but I have had probs getting into reverse ever sence I got the car... dealer says its normal.

CuddaWuddaShuda said:

I don't think that's a good swap. Think about what happens when you put in a T56. The T56 has a much steeper first gear ratio, and you'll have to put in 4.10:1 rear-end gears just to get the same overall first-gear ratio as stock 3.27:1 gears with a 3650 would yield.

At the same time, the 6th gear in the T56 has a numerically higher ratio than 5th on the T3650. So you will rev even more than a 3650 would with 4.10s, while getting the same overall torque multiplication as a 3650 with 3.27s, and shifting three times in the quarter-mile instead of two. Oh, the T56 is heavier, robs more power through parasitic loss, and costs at least twice as much.

Am I the only one who thinks this swap is just dumb? That was a rhetorical question. I know most of you would give your left nut to have a T56.

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Any thoughts? Nobody can seem to answer me why they would put in the T56. Did I just forget how to multiply when I posted this? Anyone? Anyone? Bueller?

I think you should check your math. 1st on the T56 matches the 3650 with a 3.73 gear. The rest are all improved in terms of torque multiplication through the drive line.

I agree that any conversion to a T56 requires a rear gear upgrade to match the low gear performance of the 3650. What you are not accounting for is the tremendous improvement in "staying on the torque/HP curve" which the T56 produces. Especially in an engine like the Cobra 4.6 where dropping down below the peak can adversely affect performance. The 1-2 shift on the 3650 produces a big torque/HP dropoff compared to the T56.

Using a 4.10 will produce an additional improvement across all gears compared to the 3650 (16-25%) and that's why it makes sense. In addition, the T56 will produce 6th gear (.62 vs. .67) results with the 4.10's similar to what the 3650 can do with 3.73's.

Finally, the enormous increase in ruggedness locks it for the T56. The small amount of additional weight will more than balance against the increase in reliability and efficient use of the Cobra's power production characteristics.

Otherl, broader torque curve motors may benefit less from the T56's advantages, but the ruggedness still remains.

soundguy said:

I think you should check your math. 1st on the T56 matches the 3650 with a 3.73 gear. The rest are all improved in terms of torque multiplication through the drive line.

I agree that any conversion to a T56 requires a rear gear upgrade to match the low gear performance of the 3650. What you are not accounting for is the tremendous improvement in "staying on the torque/HP curve" which the T56 produces. Especially in an engine like the Cobra 4.6 where dropping down below the peak can adversely affect performance. The 1-2 shift on the 3650 produces a big torque/HP dropoff compared to the T56.

Using a 4.10 will produce an additional improvement across all gears compared to the 3650 (16-25%) and that's why it makes sense. In addition, the T56 will produce 6th gear (.62 vs. .67) results with the 4.10's similar to what the 3650 can do with 3.73's.

Finally, the enormous increase in ruggedness locks it for the T56. The small amount of additional weight will more than balance against the increase in reliability and efficient use of the Cobra's power production characteristics.

Otherl, broader torque curve motors may benefit less from the T56's advantages, but the ruggedness still remains.

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You do point out some things I hadn't thought about, but I don't agree with everything you say. I still think that the T56 with 4.10s gives less torque multiplication in first than the T3650 with 3.27s (see below).

Maybe you're talking about the Cobra "R" T56. It has shorter gearing than the rest of the T56s, but how many Cobra "R" transmissions are there floating around? Are people putting the Cobra "R" transmission in their GTs? Maybe so. But even that T56 falls well short of the T3650 in first gear (2.97:1 vs. 3.38:1).

Every source I have shows '03 Cobra T56 ratios of:
2.66, 1.78, 1.30, 1.00, .8, .63
Every source I have shows T3650 ratios of:
3.38, 2.00, 1.32, 1.00, .62

If you put 4.10s behind the T56, you will have overall ratios of:
10.91, 7.30, 5.33, 4.10, 3.28, 2.58

If you put 3.27s behind the T3650, you will have overall ratios of:
11.05, 6.54, 4.32, 3.27, 2.03

As I stated before, the T3650 has a shorter first and a longer overdrive, which (in both cases) is exactly what you want.

It is true that after first gear, 4.10s behind a T56 give more torque multiplication than a T3650 with 3.27s. Most people run their T3650 with 4.10s, though, giving ratios of:

13.86, 8.20, 5.41, 4.10, 2.542

To get the same first-gear ratio from an '03 Cobra T56, you'd have to put in a set of 5.21:1 rear-end gears. Even with the Cobra "R" T56, you'd need 4.67:1 rear-end gears. I don't see many of those sizes! Besides, once you jack the rear-end ratio up too high, you start running into gearset (and housing) durability problems.

As far as keeping the car in the torque curve goes, think about a hypothetical 1/4mile race betwen two identical cars, one with the '03 Cobra T56 and another with the T3650. Assume they both have 4.10s. In my experience, the cars will use gear 1 through 4, and in all four gears the T3650 car will get more torque multiplication, except in fourth where it's a tie. In first, the T3650 car will use 13.86 vs. 10.91 for the T56 car. Second gear, the T3650 gets 8.20 vs. 7.30. Third gear it's 5.41 vs. 5.33. Fourth gear, it's 4.10 for both cars. The T3650 car will win this race every time.

If you give the T56 car in the above example the Cobra "R" transmission, it will have overall ratios of 12.177, 8.487, 5.863. and 4.10. The T3650 still has a big (1.683:1) advantage in first. The T56 gets a slight advantage in 2nd and 3rd (.287:1 and .453:1), and it's a tie in fourth. So even assuming you can get your hands on the Cobra "R" transmission, and put 4.10s behind it, it still doesn't necessarily beat the T3650 with 4.10s.

In fact, I'd still bet on the T3650 in that situation. Realize that the first gear ratio is the most important in the 1/4mile, for a simple (but often overlooked) reason: a higher overall ratio in first will allow you to leave the line at a higher RPM without spinning the wheels. Most people agree that launching with good RPM, and without spinning, is the key to racing the GT.

And what about a hypothetical 1/4mile drag race between a stock (3.27 rear) T3650 car and an otherwise-identical car with the '03 Cobra T56 and 4.10s? The T3650 driver only has to shift twice, vs. three times for the T56. You can count on some lost time there... I'd guess at least 0.3sec, probably more. Plus you have to consider that the T3650 will have more multiplication in first. Yes, the T56 will have more in 2nd and 3rd, but while the T56 driver is shifting into 4th (4.10 overall), the T3650 driver will have the gas floored and will be winding out third (4.32 overall)! I am pretty sure the T3650 car will win this one as well.

I haven't even touched on parasitic loss, weight, etc., all of which work against the T3650. Also, some people race the 1/8th mile, where the T3650's shorter first gear will help even more

All of this is posted to point out that Ford knew what they were doing when they were sorting out the '99+ driveline. Most people would never think that a GT with 3.27s could hang with (much less beat) a GT with an '03 Cobra transmission and 4.10s.

well worded post CuddaWuddaShuda.

ZIPP0 said:

well worded post CuddaWuddaShuda.

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Wow, this is almost the first time anyone has agreed with me.

Well I won't argue with you either. I just haven't heard as many complaints about the T-56 as I had the TR-3650 and after my 3 bad experiences that would be enough for me to do the swap, but after reading the latest issue of 5.0 & Fast Fords I might put the Viper 6 speed in it. I dunno though but big changes are coming this winter though

psnous said:

Well I won't argue with you either. I just haven't heard as many complaints about the T-56 as I had the TR-3650

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The T56 is virtually indestructible. The T3650 is much more fragile. I just want everyone to understand the tradeoffs involved.

psnous said:

after reading the latest issue of 5.0 & Fast Fords I might put the Viper 6 speed in it.

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I wonder what the Viper ratios are. I was reading something about Camaros, and I got the impression that the ratios for the Camaro T56 are even steeper (lower numerically) than the '03 Cobra version. The first gear is still 2.66, but the overdrive is 0.5:1.

psnous said:

I dunno though but big changes are coming this winter though

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What have you heard about the transmissions? Are they ditching the 5-speed? Personally, a six-speed is not really something I want to pay for, since I rarely take my Mustang on the interstate. (Too many idiots, too many flying rocks and bugs.)

Yeah, I too have trouble shifting into reverse on my 2000gt with under 30,000 miles. Also it feels as if the 1-2 shift is getting alot ruffer, not as smooth as when I bought it. Hope Ford opens there eyes and does something about it.

Concerning the t-56 argument

I've never met a person who upgraded too a t-56 that regrets it. Simple as that.

Josh

WOODY COULDY,
You have made a basic error in your logic. Most folks are installing an after market T56 . This box has a different ratio set than the 03Cobra T56. 2.97 / 2.07/1.43/1.00/.80/.62. The low end multiplication is still a hit , but not what you have assumed.

Is this thing still going? I have been trying to get something done on my 2003 GT since I bought it, but the Ford mechanics just say they "don't feel anything". And in a large part, this is true, since the problem largely (but not totally) goes away when the tranny gets warmed up. I live in Florida; I can imagine what you people in the frozen north are going through. I just happened on this site by accident, and was surprised to see so many with my problem! I'm with the guy who says it doesn't matter whether we paid $25,000 or $100,000; we paid for a new car with no problems. What's the latest on the potential class-action suit?

chuck deming said:

Is this thing still going? I have been trying to get something done on my 2003 GT since I bought it, but the Ford mechanics just say they "don't feel anything". And in a large part, this is true, since the problem largely (but not totally) goes away when the tranny gets warmed up. I live in Florida; I can imagine what you people in the frozen north are going through. I just happened on this site by accident, and was surprised to see so many with my problem! I'm with the guy who says it doesn't matter whether we paid $25,000 or $100,000; we paid for a new car with no problems. What's the latest on the potential class-action suit?

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Have you changed out your factory fill ATF yet?

GiddyUp!

Golions said:

Have you changed out your factory fill ATF yet?

GiddyUp!

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Not yet. 6000 mile service coming up; I will try it then. Both trips to the 2 Ford service shops I've been to, noone mentioned the option of doing that. Guess that would start the "lemon law" ball rolling if it didn't work. But to be fair, I will try it.

Well got my second new trans. Guess what, the 2nd gear bump is there. Gotta love these trans. I have a total of 10,120 miles on my car.

I wouldn't wait to have it done, I'd do it myself ASAP. Put some Royal Purple in there.

psnous said:

I wouldn't wait to have it done, I'd do it myself ASAP. Put some Royal Purple in there.

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I would try anything before taking it to the dealer. Only if all else fails.

GiddyUp!