Transmission recommendation

[fastback 427]

I am looking to upgrade the toploader in my mustang. It has to be kept a manual, no fluid couplers thingies. My engine was upgraded a bit so I don't think the toploader will hang in there too long. Thoughts on jerico, g force? Don't want to cut the car up to bad to make it fit.

[1967FEGT]

A stock Toploader will handle well over 600 HP. 

[fastback 427]

Yes, I will be making closer to 700. Also starting to get sick of breaking stuff...  4 to 5 thousand rpm launches are hard on it. Thinking it's on borrowed time.

[1967FEGT]

I have 557lb torque and 612 Hp in my 67. I don't drag the car but I am not concerned about launching the top loader. David Key also can make it hold up without issue.

[hbstang]

tr-3650 with upgrades.this will fit you tunnel.can be built to 700-1000 hp.
https://www.gforcetransmissions.com/tran_3650.asp
from what i read about them,when built they shift better than the tko trans and will fit the tunnel in 65-70 mustangs.dont forget it is 5 speed with overdrive!
the adapter plate will bolt into a toploader bellhousing,and the make the correct length insput as well.

[cjshaker]

I have 557lb torque and 612 Hp in my 67. I don't drag the car but I am not concerned about launching the top loader. David Key also can make it hold up without issue.

Drag strip launches are altogether different than using a trans on the street. At 600+ hp, you're going to have an issue on the strip, with a toploader. At 700+, you're living on borrowed (short) time, no matter who builds it. You only have 2 options for gear ratios also, unlike the Jerico or G-Force.

Jaime, I really like the Jerico DR4-4 that I put in my Mach 1. It does not have road race sliders, so it's not quite as street friendly, but sure as hell works on the strip. The biggest plus about the Jerico is that it's a bolt-in in place of the toploader. The only place I had to cut was for the Long shifter, and I had to notch the tunnels front crossmember to get the straight linkage to work. I think the G-Force needs some clearancing in the tunnel, but not 100% sure about that. But the driveshaft and crossmember has to be changed, so that's added expense.

Here are the cuts I had to make, but if you use the standard Hurst shifter and regular linkage, none of this is necessary.

[jayb]

+1 on a toploader NOT holding 600 HP at the track.  Seen too many of them blown up at 500 HP.  Street tires and race tires are two different worlds when it comes to transmission life.

I have a T-56 Magnum six speed in my 68 Mustang and flat out love the thing.  I believe it is rated at 700 ft-lbs of torque, six speeds, 0.64 sixth gear overdrive, etc. etc.  A lot of guys here run the Tremec TKO 5 speeds and those are supposed to be very good also.  An overdrive is a great addition, IMO, because you can run a decent rear end gear and not pay the penalty of high engine speeds going down the freeway.

[wowens]

The TOO 600 is rated 600 lb ft of torque but is close ratio with a 2.87 1st gear. I've  had 3 with all the bells and whistles from Liberty including face plated 2nd, 3rd & 4th. Lightning shifts with OD and "OK" on the stret. Weak point is 3rd gear, broke all 3 of them on the street short shifting but took 10:30 passes on MT dot  drag tires.
700 HP 67 fastback.

[Gregwill16]

Jay I have heard the T56 requires more clearancing than the TKO on a 67-70 Mustang?

[e philpott]

G Force is the strongest of those two

[jayb]

Jay I have heard the T56 requires more clearancing than the TKO on a 67-70 Mustang?

Probably true, on my car I had to cut away that reinforcement rib that the original trans mount bolts to, and goes all around the top of the tunnel.  Basically took it out about 2/3 of the way around the tunnel sheet metal.  The new mount for the trans doesn't use that reinforcement though, it goes right to the subframe rails, so it wasn't a big deal structurally.  The shifter fit right through the stock shifter hole, and right through the console, which was nice...

[Hipopinto]

Jamie

Is your Toploader a 1 3/8 input and 31 spline output?

The big one is surely The stronger Of the choices

Is your car a race car or a hot street machine?

I have always been told that what breaks them is when it hooks hard

I’m just curious as the Toploader will fit your car with no modifications and put the shifter in the right spot

There are also rebuild kits to the Toploader that can help make it stronger David Kee has the premium bearing kit which is supposed to make it stronger but all of my rebuilds went back to stock build

If you have any questions feel free to ask I will try my best to assist

Dave

[blykins]

The right clutch can make the difference on running a Toploader (or any transmission).   With that kind of power, you almost need a "slipper" clutch. 

Lots of new Toploader input shafts are made in 1-1/8x26 now and I would argue that those are the strongest out there.   They will hold about 1000 hp in other transmissions.  I know that the input shaft is not necessarily the weak link in a Toploader, but I've seen lots of twisted splines on factory pieces.

The TKO 600 is a great trans if it's prepped correctly.  If you're shifting above 6000 rpm, it will take a lot of prep unfortunately. 

Never been a T-56 fan but they seem to address some of the weaknesses of the TKO 600.   FWIW, when comparing the two, the T-56 is longer, bigger around, and heavier, so it may make it harder to fit in some vehicles.   Also a lot more money.  Depending on the engine, rear gear ratio, and where you do your most driving, the extra overdrive may never get used.

If I were drag racing only, I'd be looking for a Jerico. 

[fastback 427]

I purchased my toploader already built about 15 years ago, with all the Dan Williams goodies available. I wouldn't call my car a drag car, maybe more hot street. I like to race it on the track a couple times a year. It has called tracs and before the engine upgrades it did a 1.5 60ft and pulls the front wheels about 40 feet. It hooks and leaves hard. The engine upgrades were adding 30 cubes on crank, more head cfm, huge cam upgrade. Diamond Pistons, molnar power adder rods. It is set up for a small shot of nitrous, maybe 175, but probably won't spray it. To be honest I've been thinking about a jerico for awhile, as the cost seems reasonable and pretty much a bolt in deal.  Also the slipper clutch would be great, but have no idea on setting them up.

[Rory428]

I have broke 31 spline Toploader mainshafts on my 70 428 CJ Mach 1, running mid 12s on slicks, and have also broken a 32 spline mainshaft in my Jerico DR4 with a McLeod "Soft Lok" slipper style clutch. When drag racing with slicks, stuff does sometimes break. But these cars all had many hundreds of high RPM launches with slicks before they broke. There is a huge difference in the stresses experienced in a 500 HP car on street tires, to the same car launching at 6000 RPM on slicks. The street tires and road surfaces can be considered to act as a drivetrain "fuse". With slicks, any potential weak links can be discovered fairly quickly!! That said, it will be interesting to see how well my small spline Toploader holds up in my heavy, 428CJ powered 59 Ford ! Although many of these newer HD 5 & 6 speed OD transmissions claim to be rated for high HP & torque, my understanding is the torque capability claim is at a continuous load, a high RPM launch on slicks is very different. Also I have heard most , if not all of these "modern" 5 &6 speeds do not take kindly to full throttle high RPM powershifting. If you have to lift for every gear change, whats the point of racing with a stick?