The Definitive Automatic Transmission Thread?

There is a car with a 4L60 or 4L80 in it. The problem I see, beyond the difficulty or conversion, is that the fourth gear is an overdrive and the first three ratios are similar to what we already have. Off the line the car will still be a pig without a change to the final drive ratio.
A "loose" torque converter will liven it up a little by allowing the motor a few more revs when taking off. These torque converters are not for everybody and will change the calm demeanor of the car.

 

The TH400 saps a lot of power out of an engine not to mention its heavy which is why many people drag racing muscle cars (back when I did) swapped out the 400 for a built TH350.

 

A TH200R4 is what Grand Nationals run and they come with a multi pattern bellhousing to fit buick/olds/pontiac as well as the chev pattern like ours accepts. I would be inclined to use one of those and no electronics other than a switch to engage lockup when I want it.

 

Mine had a 4L60 with an MS shift setup and slaved to MS engine management. Despite the 4 speed and twin turbos, off the line the difference between stock 400i and TT version wasn't that impressive. Once the boost came on, that was a different matter and shifting could get scary but overall the benefit was a more sedate cruising RPM. Had I kept the car, I would have considered putting a Richmond 6 speed manual. I did that in my '85 XJS V12 - completely transformed the car.

 

Hello. Do you have any pictures or other details on the swap? Who made the custom tail piece or adaptor to connect the transmission to the torque tube?

 

If a 4L80 will fit in the tunnel I wonder if it would be worth contacting these guys to see if they are interested in making up a conversion kit to fit their 6 speed auto in. They advertise that they make adaptors to fit it to any engine. If they could fit it up to a torque tube as well it could be a possibility.

6x Six-Speed GM 4L80E Automatic Transmission (850hp) - TCI® Auto

It would be a nice conversion with the 5 gear 1:1 & an overdrive as well.

 

Cost is the issue, not if it can be done. The problem is the torque tube and the adapter ferrari made to replace the TH400 tailstock. To make that part would be time consuming so who pays for that development time? Ive considered it using my own 400 as a test mule but I just havent had the time. The other problem is the TH400 tailstock is larger in diameter than the rest of the transmissions from GM. The coupler for the torque tube is now a problem assuming the chosen transmission is the same length as the TH400. Do you ditch the torque tube and run a conventional driveshaft? Thats one thought but then you need a transmission crossmember and additional mounts for the rear diff but no adapter required and the transmission length is now a non-issue. My car is super clean and correct so welding or modifying the frame to accept additional mounts to do a trans conversion isn't an option so now Im back to making the adapter....

 

There is just so much to overcome(pay for)when considering a swap to another auto trans., with little benefit from it.
For all the work involved swapping to a non-Ferrari manual makes more sense and might even pay for itself in retail value were you to be inclined to sell. I'd not de-value a car for not being pure Ferrari when a F gear box costs an arm and a leg, then the other arm and leg to overhaul it someday.
I'd still like to see some 7 or 8 liter V-8 Detroit iron in one of these, the TH400 would be a non-issue then.

 

I see a mis-worded where I said the tailstock is larger in diameter. I meant to say tail shaft or the splined output shaft is larger in diameter. The TH350,700,200R4 all use the same slip yolk, the TH400 is by itself.

Im not sure why ferrari chose the TH400 trans vs a 350 because the TH400 is over-kill, its a truck transmission!

And what I didn't mention was the downtime for whoever takes this on. I personally dont want my car laid up with no transmission in it for what could be a year from beginning to end, develop a kit for whatever dollars invested and have 3 people step up to the plate for the parts.

 

The physical size of the TH400 might have been one reason to use that gearbox.

You can think of the 400 driveline as a simply supported beam - supported at each end by the (same) rubber mounts. There is some bending load at the back of the transmission where it connects to the torque tube so the rear of the transmission in this application has to be strong/big enough to cope with this load. Maybe it was thought necessary to use this case for strength (or maybe it was easy to adapt to a torque tube arrangement to the back of this box).

Like Newman said, anything can be done if you throw enough money at it, but converting to an open tailshaft is not a reasonable option.

The torque tube arrangement eliminates any rotational torque from the mounts - the driveline does not tend to rotate under load. A change to an open driveline means the diff mounts and the engine mounts on the chassis probably would need strengthening and some torque reaction location would be required. The rubber mounts themselves are almost certainly not designed to control the torque reaction which will tend to rotate everything anti-clockwise.

If you manage to get this far then you have to consider what is going to happen to all the stuff connect to the engine as it tries to rotate - there is not a lot of clearance in the engine bay. Exhausts, air cleaners and even the radiator hoses will all need to be thought about. Expect a lot of banging and rattling from the exhaust.

There are some 5 speed manual transmissions available (Richardson, Doug Nash) that are designed to convert auto GM cars to manual without changing the diff. One of these gives almost identical overall drive ratios to a Ferrari 5 speed and will probably bolt to the auto adapter on the engine.

But then you're back to the torque tube issues............

Regards

WM

 

Ferrari(and Rolls Royce) chose the arguably strongest available automatic transmission of the day, with the Chrysler Torqueflite 727 being the slightly heavier alternative. I'd guess a vendor relationship, price or packaging were the buying criteria as either would have served equally well. As would have the Ford C6 but....
Overkill? Our 400is weigh as much as a Chevy pickup of the day did so why not? It was used in every big engine GM car of the era not just trucks.
The TH350 is a few pounds lighter, perhaps 30(edit, probably more like 10-15#). I've not weighed either but have lifted both more than few times.
A TH350 in drag race trim with today's technology might be as strong or even stronger but "in the day" the TH350 was a weenie that wouldn't last long behind a powerful engine.

 

I think Bill26 is onto something regarding the strength of the case as a stressed member in the powertrain. The 350 is significantly smaller.

The weight of the car isnt so much the issue, the engine cant pull the skin off a rice pudding so it would never tear the guts out of a TH350. And I know they used the 400 in cars, I had a 396 caprice with one.

 

Ferrari(and Rolls Royce) chose the arguably strongest available automatic transmission of the day, the Chrysler Torqueflite 727 being the slightly heavier alternative. I'd guess a vendor relationship, price or packaging were the buying criteria as either would have served equally well. As would have the Ford C6 but....
Overkill? Our 400is weigh as much as a Chevy pickup of the day did so why not? It was used in every big engine GM car of the era not just trucks.
The TH350 is a few pounds lighter, perhaps 30. I've not weighed either but have lifted both more than few times.

 

Jag also used the TH400.

Maybe GM was having a fire sale.

 

Rolls and Jensens chose the 727 transmission because Rolls used the Chrysler 360 c.i.d. block as the basis for their engines of that era. They licensed from Chrysler then made their own blocks, and, bored and ported to their own specifcations..Jensen Interceptors were straight-out Chrysler 440's. So why re-invent the wheel? The 727 transmission is the obvious choice since the 727 was conceived for these engines. I hope that is of some help to someone. Jq.

 

I believe the Roller "L" V-8 of the era dates to the fifties and is RR designed and built, no connection to Chrysler's "LA" V-8. No torqueflite behind it I ever heard of, they absolutely did use GM's TH400 among other things sourced from the general.
Jensen did use the 727, my friend's shop currently has a semi basket case mark III waiting for my attentions.

 

That may be the case but an independent Rolls guy told me the architecture is nearly identical and a lot of Chrysler parts will drop straight in - manufactured in the same plant, different box , Rolls part 10 times the price..

John

 

I see no reference on-line to chrysler power even in the slightest in a RR. And we're veering off topic slightly lol

 

I don't other than what can be found on the internet. The conversion was done by Historic Race Engineering of Costa Mesa several years ago.