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By 312YBlock - 3 Years Ago
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I have a 312 with an E4 cam in my 55 with a 3sp OD and am seriously considering replacing it with a Tremec T-5. The 1352-000-251 model is rated at 300 ft-lb torque, which sounds like it should do the trick. What are your thoughts? 🚗
Questions that come to mind are:
Shifter position, speedometer accuracy and seat travel
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By Joe-JDC - 3 Years Ago
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Street, or occasional drag strip use? Street will be just fine, but if you drop the clutch and try to drag race, third gear will go away very quickly. The T5-Z is the best of the T-5s, and after that you will need to step up to a 3550, or TKO-500, TKO-600, or new TKX. I am doing that same conversion in my '55 Thunderbird with a 345Y and -Z Tremec. Joe-JDC
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By 312YBlock - 3 Years Ago
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It will be street driven, good info. Thank you Joe, I really appreciate the feedback.
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By Florida_Phil - 3 Years Ago
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Joe-JDC (8/4/2021)
Street, or occasional drag strip use? Street will be just fine, but if you drop the clutch and try to drag race, third gear will go away very quickly. The T5-Z is the best of the T-5s, and after that you will need to step up to a 3550, or TKO-500, TKO-600, or new TKX. I am doing that same conversion in my '55 Thunderbird with a 345Y and -Z Tremec. Joe-JDC
I have also considered this for mod my 55 Tbird. Will a T-5 transmission fit into the tunnel of a 1955 Tbird without modifying the tunnel? Is the Mummert adapter kit a bolt in? I assume you will need a new driveshaft?
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By charliemccraney - 3 Years Ago
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A -Z T5 has worked fine in my truck for the past 12 or 13 years. Keep in mind that while the T5 isn't the strongest transmission, it came behind V8 Mustangs, Firebirds, Camaros, etc and holds up well in those. 300-350ish hp and street tires is probably not much of a threat to it. The -Z T5 has a tall overdrive so you could need a pretty short rear gear to make it cruise well on the highway, depending on the engine build.
Can't help with 'Bird specific questions.
It looks like the 1352-000-251 may be the -Z transmsission, the Tremec part number, rather than the Ford part number, which has the Z.
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By 312YBlock - 3 Years Ago
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I’m going with the Z model, below is the part number. It will fit the tunnel but the floor will have to be cut to accommodate the shifter, an offset lever can be installed to move the shifter closer to the stock position.
Ford Performance T-5 Super Heavy Duty 5-Speed Transmission M-7003-Z
Summit Racing Part Number: FMS-M-7003-Z $2,228.99 current price.
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By charliemccraney - 3 Years Ago
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On Jegs, the 1352-000-251 was just over $1800. Investigate. If it's the same, save yourself $400.
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By Joe-JDC - 3 Years Ago
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I have a T5-Z behind my 383W in my '86 Mustang GT, making ~460 hp. With 100 hp shot of N2O, it pulls the front wheels in full street trim. The center force clutch is the weak spot after the 28 spline axles. I also have a 306W in my '91 LX Coupe with T5-Z, and it puts 293hp to the wheels in full street trim. I don't think the T5-Z will be the weak link with a Thunderbird. Great driving street transmission with an aftermarket shifter. Joe-JDC
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By 312YBlock - 3 Years Ago
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The -251 isn’t the Z, the -251 is not as robust.
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By charliemccraney - 3 Years Ago
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Have you checked? same gear ratios, same torque rating. Since those are the same, I'd really want to know what I'm paying $400 for.
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By 312YBlock - 3 Years Ago
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You need to compare the two, you will see the difference, it’s not in the ratios it’s in the guts. The Z is a stronger box, the -251 would be fine I’m sure but I like a little insurance.
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By Dave V - 3 Years Ago
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I have that setup in my 56 Fairlane. 312 with E4 cam, 251 T5 trans. No issues at all even driving it hard. Love it
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