[joe69judge]

Hello,
I am currently looking into installing the Tremec Magnum 6 speed transmission into my 69 GTO.

Has anyone dealt with these company's ?
Silver Sport Transmissions
Modern Driveline
American Powertrain

My GTO specs:
- Original YS 400 - bored 40 over
- Holley Sniper Quadrajet EFI
- MSD Dual Sync Distributor
- stock intake
- Muncie 4 - speed
- 3.90 rear
- used for cruising

thanks

[Gator67]

Bought a T56 Magnum for my 70 Formula from Bowler. Haven’t installed it yet, but have called them on multiple occasions to ask questions, and they’ve been very helpful.

[JLMounce]

I spoke with Silversport on several occasions about at TKO600 before I decided to stay automatic. They were nice to deal with and the tech's were well versed.

No other real world experience there.

That said, based on your specs, I think the T56 Magnum is probably overkill. I would run the TKO600 in it's place. The forward gear spread is about the same as the T56, but just slightly taller. That IMHO would be better considering your steep 3.90 gears in the rear. The TKO600's overdrive ratio is a .64 compared to the T56's .63, essentially the same.

So the only thing the T56 gains you is the intermediate .80 overdrive gear. If you spend a lot of time at 50mph, that intermediary gear may be beneficial, but if not, you can probably save some money and some struggle on installation by going with the TKO600.

Just my .02

[ID67goat]

I have a T56 in my 67. I was tired of cruising down the highway at 3500-4000rpm. I did this back in 2002 before there were all the choices that are out there now. With 0.5:1 overdrive I can cruise 80 mph at about 2k rpm....which is a little too low with my cam etc, so I am usually running in 5th gear most of the time.

If I was to do it over again today I think I would go with a TKO600 as it appears that there is a lot less mods required to install them. With the T56 I had to totally cut out the trans tunnel and fab a new one, fab a new crossmember, new driveshaft, adjustable upper control arms to correct pinion angle, new carpet, shift boot, hydraulic clutch, etc.

As far as the companies listed....Modern Driveline is local to me and I have purchased parts from them. The owner Bruce gave me a tour of their shop and everything there was top notch. Originally they were primarily geared towards Mustangs, but it looks like they have developed quite a few kits for other makes.

[darbikrash]

Modern Driveline sold me the TKO600 in my '64 Catalina. They were great to work with, competitive pricing, and Bruce knows what he is doing.

[cdrookie]

I had to cut and fab a new trans tunnel, redo my crossmember, hydraulic clutch(I have headers), driveshaft, adjustable upper control arms, and other bits and pieces when I put a TKO600 in my 75 Lemans. The T56 is such a large transmission it wouldn't be fun if you're doing the work yourself in the garage. For your purpose I'd do the 600, still not easy, but easier than installing a T56.

[chuckies76ta]

I dealt with Silver Sport back in the day when it was called Keisler. They were great to deal with. Also dealt with American Power train. Both are great companies. I have a TKO-600 with the .82 od. Most people seem to prefer the .64od. The .64 was no good to me here in Canada as the top speed limit is 110 klms or 70 mph. I also didn't like the drop in ratio. .72-.75 in these tyrannies would be a good ratio imo.

My car is strictly cruising also. I also looked at the Tremec Magnum 6 speed, but again the 6th gear was no good to me as I would have to be doing 80 to 90 mph to use it. Like ID67goat says, he runs around in 5th gear.

The TKO600 like other have mentioned is probably best suited for what your doing. again IMO.

I run a 28" tall tire with 3.73's. With your 3.90 gear the .82 won't be as nice as if you were running lets say a 3.42-3.55 gear. The .64 might work better in your case.

What you need to do is first find out where your engine cruising nicely with you cam. In other words, where the engine doesn't buck or start hesitating. Once you have that info, move on to where you want to cruise on the highway with your setup. Ex: Tire size, RPM, Speed. Go to Silver sport and use there speed calculator to determine what will work for your setup. https://shiftsst.com/speed-analyzer

Here's another nice option I did to my car. I install a hydraulic clutch. https://www.summitracing.com/parts/awr-hmgm01101sr

Charles

[Half-Inch Stud]

No. have not. Yet Stock tunnel for 4L80, slide stock crossmember back

[6 Grrrs]

Nick Lingua has the SilverSport T56 swap in his '67 and speaks very highly of it. I'm doing a Richmond 6 speed OD trans in my '66 now, because I do not want to cut the tunnel.

I have run a T56 in my lowered 454ss pickup for 20+ years. T56s do not like no lift 1-2 shifts. Great otherwise. I run 4.56 gears in my 454ss with the .50 OD, I run 2100 rpm at 70mph on a 29 in tall tire.

[goathead455]

I installed a T56 magnum in my 70
I have dealt with American powertrain but just for a crossmember.
It is a great transmission.
I agree with the people saying that a TKO 600 would fit your needs perfectly
You need to cut the floor with either transmission
Each one will require a shortened or new driveshaft
With the T56 you will need a bellhousing or an adapter and a crossmember
The TKO will work with the bellhousing you have and the factory crossmember will work, it just needs to be moved back a bit.
Both transmissions are excellent and you will be very happy with the upgrade.
The T56 will require a bit more work and more parts.
Both have 26 spline input shafts

[pokey1]

I installed the T56 magnum from Silversport. I went with the whole kit that provided everything I needed including bellhousing, clutch, hydraulic throwout bearing, crossmember, driveline. Even included sheet metal and templates for tunnel work, Thorough directions for each step and great tech support. Shifter location is even set up for installation of my original console. I love it.

[428goat]

Used Silver Sport and great to work with. I put in a Tremic 5 speed. Had to cut the tunnel other than that no problem.

[lust4speed]

We put a Tremec 6-speed in a friends 64 Tempest wagon and basically had to remove the tunnel and start over.

We recently installed a TKO-600 5-speed in a friends 67 GTO about two months ago and there was no cutting and just a few dimples in the tunnel where the corner of the top plates would have touched. Silversport machines the cases so that the cover plates sit lower and they also remove other protrusions that aren't needed on a retrofit install making the trans into a smaller package.

Today we did the preliminary first install on my 67 GTO with my TKO-600 and found the same thing except we had a little extra room over the first GTO install. Both transmission packages were purchased from Silversport with their complete sure-fit kits. My kit included a shallower trans mount and the trans had 1/2" clearance around the top without any bodywork. I'm going to use a standard mount and will dimple the tunnel to maintain the original engine/trans angle.

We won't get back to the install for a few days since my voluntary crew will be tied up with work and other commitments, but I'll get photos taken as we do the final installation.

Here's a photo off the internet of a 6-speed next to a Muncie. It was enough to kill any thought of installing that in my GTO. Also the one we put in the wagon had a fifth gear that was okay over 65, but shifting to sixth dropped the RPM's down to about 1,200 at 70 MPH with its .50:1 ratio.

[Formulabruce]

I believe Silver Sport sells a NO mod kit. I know they do for the second gen Firebirds. Great people to deal with and you get a custom drive shaft built for your car.
Silver Sport has a 10-10 lay away that you can use to start your warranty when your car is done, or just as a pay as you go.
They have a 3 year warranty too.

[joe69judge]

Great replies. Thanks ! I got the Silver Sport 6 speed magnum kit a little over a month ago and currently installing it. I upgraded to the hydraulic clutch and that came with the Quick Draw bell housing.

[65madgoat]

5 speed TKO Tremec install videos with a 1969 GTO are here:

https://www.youtube.com/playlist?lis...HhRp_1HaZ8aewY


Either way the floor will need mild work...

Nice you went with the 6 speed and cut the floor as needed to make it work. The double overdrive will be a huge plus!

[64speed]

Installed a TKO600 in a 64 Tempest. Cut nothing but the hole for the shifter.

[65madgoat]

1964-1967 a-body is different than 1968 to 1972 I understand...

[pokey1]

The 6 speed was a bit of work but has been awesome ever since. Made a whole different car out of it. Was even able to put my stock console back in.

[dhcarguy]

Originally Posted by 64speed

Installed a TKO600 in a 64 Tempest. Cut nothing but the hole for the shifter.

Would be the same install for a 65 GTO ??
What was the total cost for the trans and "A" body kit.

Thanks ,Dave