.50 6th gear ratio swap?

[Quicktime_GT]

Anyone ever thought of this? I never do 6th gear pulls, and only use 6th for highway cruizing. Is it possible to run the 6th gear set out of an F-body car in a cobra T56? The .50 vs our .62 would result in a lot lower rpms and maybe even a tad better fuel mileage. I'd probably run a 4.10 rear gear if I had a higher 6th ratio.

I am considering doing a 26 spline input shaft, and figured while the transmission was apart, this might be something I'd look into.

Input?

I found this:
http://www.thegearbox.org/catalog/item/3838217/3508230.htm

I've emailed a guy at the gear box, so we'll see what he has to say as well.

 

[Satyr]

I am also interested in this...good question.

 

[V6&V8SHO]

op:

 

[mpe331lx]

I'm going to go out on a limb and say YES. For the most part, the internal on an LS1 and a cobra t56 are virtually identical. As a matter of fact, I installed the complete 1-4 guts (other then the input shaft) and counter shaft into a friends 04 Cobra T56 when he broke it. At the time I was under the impression that the ls1s has steeper 1-3 gear ratios, but I was mistaken. They have the same 1-4, it is the MN12 trans that's in the Zo6 and the GTOs that has steeper gears.

As for 6th gear, you would have to swap 5th and 6th form the ls1 trans, as that is one of the differences that i did notice. The cobra trans has a separate gear for 5th and 6th that rides on the output shaft. The LT1 trans has both gears fused together (one on top of the other). As long as the mainshaft/output shaft are splines and have the groves for all the C-clips in the same place, it should be a direct bolt in.

If some one has a pic of a bare 03/04 Cobra mainshaft/output shaft, post it up. I'll compare it to the LS1 shaft that I have in my garage.


BTW, Ive been thinking of doing this swap myself, as I have a complete 5th and 6th assembly from an ls1.

I found this:
http://www.thegearbox.org/catalog/item/3838217/3508230.htm

I've emailed a guy at the gear box, so we'll see what he has to say as well.

I dont think that is the complete 5-6 gear set up needed. That is the cluster that slides onto the mainshaft (AKA 5-6 driven gear 37/29 tooth). You will also need to purchase the 5th (58 tooth) and 6th gear (67 tooth).

Here is a link that has the parts that you'd need to do the swap:
http://www.tick-performance.com/tickshift/parts/ls1fbody/t56parts/


Here are some pics of the last ls1 T56 that I tore down and rebuilt (it was in bad shape):

The arrows point to which gears are which:
Red-6th driven
yellow-5th driven
They are both circled in yellow because they are a single gear cluster (I'll show it bieng pulled in another pic)

Blue- 6th gear
Green-5th gear

My custom long jaw puller, made specifically to pull of the 5-6 cluster:

You can see it is one piece on the ls1 trans. The cobra trans has 2 piece 5-6 driven gears.

And with it completely off the shaft

 

[racebronco2]

I have the .75 5th and .50 6th gear. It does require the cluster and 5th and 6th gear. It does lower the cruising rpms but it does not improve gas mileage because as soon as you barely step on the gas it goes into boost ever so slightly. It also slows down your acceleration when shifting into fifth.

 

[IronTerp]

It's actually fairly commonplace to see Terminator folks go with the Viper 5th (.75) and 6th (.50) gear swaps. As Racebronco posted, it does require the 5th and 6th gear cluster assembly as well and parts alone are usually in the $500+ range. But, a bunch of fellas have done this and certainly makes sense for those guys that have gone with 3.90 or 4.10 rear end gears.

 

[Quicktime_GT]

Cool!

the whole 5/6 thing makes more since to me now that I see that the they are made together as one cluster.

I'll see if I can put together a parts list with prices. I found some great deals on 3650 parts from a place in NY www.autogear.net , I may check there and see what kind of deals we could get.

 

[Quicktime_GT]

ehhh...

Just got an email back from the gear box

Hello
Changing the gears ratios for the 5/6 is not that simple. in the ford t56 you have to change both the 5th and 6th main shaft gears and both the 5/6 counter shaft gears and also the main shaft has to be change to accomplish this. Cost to do it would be aprox 4600.00. Please let us know if we can be of further help, thanks kevin

It sounded like such a good idea at the time..

 

[IronTerp]

ehhh...
Just got an email back from the gear box
It sounded like such a good idea at the time..

That information is not correct. Or at least the price is not......Not sure about the GM swap, but all the fellas that I know that have done this switch, all used the Viper 5th and 6th setup.

Send a PM to Wiseguy@BAP, who is a respected member and vendor of SVTP, and he'll give you the correct information and pricing for this switch. He's done a bunch of them.:beer:

 

[JB]

Liberty did mine in '03 :coolman:

 

[VirtualSVT]

ehhh...

Just got an email back from the gear box



It sounded like such a good idea at the time..

4600 bucks? You can buy a Viper Spec T56 for less than that..

 

[racebronco2]

It's actually fairly commonplace to see Terminator folks go with the Viper 5th (.75) and 6th (.50) gear swaps. As Racebronco posted, it does require the 5th and 6th gear cluster assembly as well and parts alone are usually in the $500+ range. But, a bunch of fellas have done this and certainly makes sense for those guys that have gone with 3.90 or 4.10 rear end gears.

I originally installed the gears when i had 4.10's. The best scenario would be our .80 5th and the .50 6th. I wounder if the cluster can be machined so that you can just use the 6th gear that way you will not have the dreaded drop in acceleration when shifting into 5th gear when using the .75 5th gear.
Here is a video in which i was keeeping up with a z06 until i shifted into 5th gear at about 120mph (when i had 4.10's).

ehhh...

Just got an email back from the gear box Hello
Changing the gears ratios for the 5/6 is not that simple. in the ford t56 you have to change both the 5th and 6th main shaft gears and both the 5/6 counter shaft gears and also the main shaft has to be change to accomplish this. Cost to do it would be aprox 4600.00. Please let us know if we can be of further help, thanks kevin

It sounded like such a good idea at the time..

I think it's a misprint at 4600.00, if not they are trying to rip you off and you should stay far away from them. You can buy a viper spec tranny for less then 4600.00.

 

[Quicktime_GT]

Yeah I didn't even catch that, I just assumed it was 460.00 I'm sure it's a misprint.

 

[GodStang]

I doubt its a misprint. I called a place and needed a T5 repaired. I had all the parts and it was disassembled and all I wanted them to do is put the guts back in it and that was it and they wanted $1600.

Just on a side note someone said they where taking their tranny apart to install the input shaft. You do not have to take it apart to install it.

 

[D2Fresh16]

Did this ever get solved? Did you swap the 5th/6th gears out?

 

[medrick]

i just had mine done. a little over $400 for parts from tick performance.

 

[SLPRCTM]

I did this a while back. Works great. One thing no one mentioned is it makes the car quieter while just cruising on the freeway.

There is no machining or replacing of any shafts required. Here is the part numbers from D&D Performance of the three pieces you will need.

I am giving you the tremec # followed by the D&D #.

6th speed gear
1386-087-004 / BG15

5th speed gear
1386-086-0004 / BG17

5-6 speed driven gear
1386-070-002 / BG19

Let me know if you have any questions.

 

[snakeraper11b]

.84 5th, .56 6th here, best of both worlds.

 

[racebronco2]

.84 5th, .56 6th here, best of both worlds.

Where did you get those ratio's from? I need those gears.

 

[snakeraper11b]

Where did you get those ratio's from? I need those gears.

Its a custom built T56. 26 spline input, 32 SSR spline main, M12 z06 gears and triple cone carbon synchros. Its the bee's knees. Main shaft was machined down and a journal was added for a press fit reluctor wheel for a ford VSS. The tail housing gave us a hell of a time with the modifications. It was some ford retrofit housing, modded to hell. Only hang up, it sits about 3/4" high at the rear, so I had to shim the trans mount down with washers to get the proper pinion angle. Its the perfect gear so I can hit 200 with 3.27's in 5th, if I ever get the money to start the standing mile build... Some pics of the mods.