Hey all,

So this was just an idea that popped into my head recently. It's my understanding that both GM and Ford T5 transmissions are different externally, but that the gears inside are interchangeable. It's also my understanding that the "Z-spec" T5 gears used in certain Mustang models, are stronger than the standard World Class T5 gears found in F-bodies, and many 'stangs.

Just trying to figure out if Z-spec gears would be a fairly straightforward upgrade to an F-body WC T5? I have the idea of a possible rebuild/"budget build" in mind - a mostly stock rebuild, with Z spec gears, and a re-inforced G-Force case (Since the case isn't very expensive, and should address the main weak link of the T5 in the first place. G-force gears however, aren't worth the risk IMO, for what they cost/what a TKO goes for...)

Keep in mind, this is just for a fairly mild street car in planning (A 350 making roughly 300 flywheel HP or so). It's not going to see the drag strip/sticky tires, or powershifting/other forms of abuse. If anything, it's more likely to end up as a summer cruiser, or possibly even a daily driver. Between my uses/power levels in mind, and the cost of a T56 conversion these days, I don't plan on throwing the T5 away, and I definitely don't want to convert to an autotragic

 

For a 300hp street build that will not see track get a WC t5, add a STEEL cluster plate and a pro 5.0 shifter. You should be good to go.

 

The 2.95 first V8 F-body with headset (input shaft / countershaft) gears are a stronger ratio (closer in tooth count) than the V8 Mustang units with 3.35 first. The T5-Z used the F-body ratios so that's a free upgrade; no need to change that.

You already have a 26 spline (larger minor diameter at the splines) input versus the 10 spline Ford input.

They also added a cone (tapered) bearing at the mainshaft/maindrive pilot area. You hear of 3rd gear dying in T5s; this is a fix for that. The T56 and TR6060 run the same setup but with different bearing & race numbers.

That cluster support plate is wise too.

The 28 spline Ford mainshaft isn't measurably stronger / worth the changeover.

Billet keys can be had for 1-2 and 3-4. Not sure about 5th but I think they're the same too.

If you can find an old Hurst Comp Plus with the stops, it's a nice shifting piece. I never cared for the T56 Pro 5.0 and can't specifically recommend their T5 shifter either.

If you're still running the 3.08 and a .73 5th gear, now might be the time to consider a .63 setup and shorter rear gears.

 

jmd: So, are you telling me that the F-body T5 WC gears are basically the same thing as the Z-spec mustang T5 gears, because they're already the same ratios? I was under the impression that the Z-spec gears are made out of stronger materials, but if I'm wrong, that might make things easier, lol.

I don't even have the stock shifter anymore - I replaced it with a Hurst Billet Plus a little while back - Haven't tried a Pro 5.0, but I do like the Hurst - MUCH more accurate shifting than the sloppy stock unit.

So from what it's sounding like, should I leave the internals alone for the most part, and just invest in a cluster support plate, and/or re-inforced main case? As far as the gear ratios inside the tranny go, I'm not sure if I have a .73 or .63 OD gear, but I was planning on going with a posi-diff and 3.42 gears with my rear axle.

 

Either will work for 5th. I ran the .73 for a while with 3.73. I recently switched to a .63 for better highway mpgs.

 

I've seen nothing to substantiate the parts as different.

Keep in mind the 3rd gear issue in T5s is due to a looser mainshaft piloting setup. Not the gear itself. I haven't machined those parts for that modification myself, but might in the near future.

You should definitely check the countershaft race bore for wear. I don't know how much material the G-force case adds up front where it matters; I'd consider adding something of steel there if I were building one up that needed the work.

Hanlon Motorsports is a quality T5 resource; he posts here on occasion.