Auto trans. alternatives for I6 thread!

[DansEdgli]

This has come up in a few other threads and instead of leading the original posts off topic it was suggested the topic be relocated.

As the original 4 speed auto is fairly weak and extremely costly to beef up, us I6ers after high horsepower dont have many ford options when it comes to better, stronger transmissions unless we want to sacrifice a gear and use a C4 or one of its derivatives.
We could import an AOD 4 speed Im led to beleive but this would be extremely expensive.
It has been suggested that we could use the Turbo700 transmission from the commodore/ chev engines using a castlemaine rod shop adapter, I think these sell for around $650-$700 recalling a post GM destroyer made a while back about bellhousings.
What is everyones opinion? Is it sacrilege to use a chev product in a ford regardless they are easy to modify to handle substantial horsepower, not to mention a hell of a lot cheaper than upgrading the electronic 4 speed we are used to.

Is there any other alternatives?
Thoughts, suggestions all welcome.

Cheers
dan

[WBT56]

Originally Posted by DansEdgli

....It has been suggested that we could use the Turbo700 transmission from the commodore.....
What is everyones opinion? Is it sacrilege to use a chev product in a ford regardless they are easy to modify to handle substantial horsepower,....
Is there any other alternatives?
Thoughts, suggestions all welcome.
Cheers
dan

Can't offer any alternatives, but in my experience the T700 is VERY prone to frying the 3/4 clutch pack, in V8 and V6, and are not particularly cheap to fix. All I know is that if I pull out a T700, it doesn't go back in.

[Walkinshaw]

There has been whispers that the BTR 4speed box isnt as flakey as we are lead to believe. I mean they were behind 250kw TS50's. 290kw GT's and now days 10.35sec XR6T utes.

[9psi EB]

The BTR will take 300hp easy.
Mine hasnt missed a beat at 220,000kms.
Walkinshaw is right, they have used them behind some fairly high powered engines,
They were also used behind a 335hp engine in Maserati's so they cant be all that bad.

If you are set on changing it, then contact castlemaine rod shop, they have bellhousings to fit C4's and a few others into E-series.
Also check the application guide on their website.

[Walkinshaw]

300hp.....what about 300+RWkw, so say 530bhp? i hope so.

Does anyone know what was actualy done to strengthen the box for the Tseries, and BA XR/GT's

[EB SIX ON N2O]

heat is there only real killer..... big coolers neaded

[Troutman]

I was quoted well over a grand for the TH700 kit (not including the transmission). But because the TH700s are so cheap secondhand it still makes better sense then stuffing around with trying to install the electronic BT-R into an X series or EA, then paying another $250 just to make the damn speedo accurate with the ultra-short diff you need to match the TH700's take off, then suffering with higher rpm than the TH700 on the highway after all that! No thanks.

[Walkinshaw]

when you have a bucketload of torque an ultra low 1st gear (ala TH700R) isnt neaded. The BTR has very similar 1-3 ratios to the AOD and C4,6,9,10 bboxes which are used in a bucket load of BIG bhp drag cars. The BTR box would have better ratios for drag racing than the TH700R i would say, as the 700 has a huge drop between 1st and 2nd.

[Troutman]

That's very true Walkinshaw, but I was also thinking that the close-ratio nature of the BT-R would be a disadvantage for cars with lots of torque.

In my case, for example, I'm choosing between a BT-R with 3.9s or a TH700 with 3.45s - both have a similar effective 1st ratio.

[Walkinshaw]

That is true and the 700+3.45 will have better cruising speeds.

Its not that the BTR's gears are stacked close, its rather the sever jump from 1st to 2nd on the TH700R's.

TH700+4R
1st 3.06
2nd 1.62
3rd 1.00
4th 0.70

BTR LE85/93/95/97M
1st 2.39
2nd 1.45
3rd 1.00
4th 0.68

If reving to 5500rpm, the 1-2 change in the boxes will result in this

TH700+4R
5500 (1st) ==> 2900 (2nd)

BTR 4speed
5500 (1st) ==> 3350 (2nd)

Doesnt seem much but it could be the diffrence of being on full boost and boging down.

It gets worse as you lower the shift rpm, as is the case in day to day thrashing/driving.