Upgrading the 3 speed automatic transmission

Actually, I think the auto rear diff ratio with the 700 overdrive is perfect - 120 km/h @2200 RPM, well within the torque curve of the engine and a relaxed engine speed for highway cruising.

If more power is needed or the original ratio is needed, one can select "3" and you will have the 1:1 as the stock.

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I've finally managed to track that twin turbo 400R4 400i ebay listing from 2014! It had actually been captured in this thread: https://www.ferrarichat.com/forum/threads/twin-turbo-1984-ferrari-400i.453730/page-2#post-143478535

That's the only 400r4 conversion that I know of, there are unfortunately only a few photos of the transmission

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As I've said you can see the tunel has be modified on the passenger side :

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Also read the comment from the original seller : "the 400i is more like a large rocket, at first not much happens but when it goes, you better be strapped in…"

Then from the buyer "I am very fastidious and despite all that the car didn't do for me primarily because of the automatic transmission which doesn't quite work" (...) "Bottom line, the car is an interesting bird, a fair amount of money has been invested to get it to where it is, what kills it is the automatic transmission"

 

Knowing GM there is probably commonality between them for mounting bolt pattern. If not as said it already has an adaptor plate on the back of the block.I dont see length as an issue either.The same talent for lengthening or shortening drive shafts or differential axle tubes can do it. It may require stronger materials for the torque tube than for a drive shaft. Same with the drive shaft. If you can make an axle you can make a new drive shaft for a 400. Also in modifying the tail housing to accept the torque tube external strengthening can be done and I agree it probably needs it because it was not designed to rigidly hold a 6 foot long lever.

 

For all the work involved couldn’t you also fab a crossmember for a rear transmission mount?

 

Not a good idea. 2 mounts on engine and a rigid connection to the diff with 2 mounts. Its a stable unit. Add additional mounts between creates an alignment problem

 

These are the dimensions:

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Interesting thread and I've debated a 4 speed auto swap myself but dropped the idea for a couple of reasons. I'm not sure if the 700R4 case is strong enough to be in a torque tube arrangement. I see the twin turbo example has one but that doesn't tell me if it's going to fail at some point. I would want to see the wall thickness of the transmission just ahead of where the tail stock bolts on. Seeing the tunnel of the car has to be altered that would kill the conversion for me right there. Cost and down time working on my own car is another factor. I hate working on my own cars, hard to explain why, I just do. So for me the better converter / different 1-2 ratios and lighter rotating mass makes sense. Yank the trans, drop it and a pile of parts at the local auto trans shop I've used before and stick it back in when its ready. Keeps the car original too.

 

Me too. 3 Italian cars is enough. Not looking for more to do. Like ti get rid of one actually.

 

I already purchased a 2.75/1.57 gear set, I will do this first.

Another easy improve is to change the stall speed of the torque converter and add a shift kit improver.

All these combined should make a significant improvement.


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I’m late to the party but has anyone contacted Gearvendors. That was a go to for me many years ago. It’s only money

 

Not possible, there is no space for it to fit.

 

Will going to the lower first and second gear have any adverse effects on the kick down feature?

 

The kick down is vacuum operated and has no relationship with the speed of the car.

The obvious difference would be that when it downshifts, it would go to a higher RPM.




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No. The part throttle up/down shift is adjusted based on the vacuum valve, whereas the full throttle kickdown is triggered by the micro-switch and kept until the regulator reaches a defined level of rpm.

This regulator is similar to the ones you would see in old-school steam machines: the rpm setpoint is defined by the weights that are atrached to the regulator "arms".

 

This is the microswitch.

Some corrections: What you mean by the "regulator" is the governor, the (pressure) regulator is something else.

The function of the governor is to set the shift points, NOT the kickdown.

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Not sure about your picture, looks like a solenoïd (insde the gearbox)/ The kick-down micro-switch is attached to the throttle cable. Here is a previous picture of the the switch posted by @Al Campbell.



The transmission does take into account both manifold vacuum (vacuum modulator) and rpm (governor),

When you activate the kickdown, the gearbox will raise the shift point to the maximum that will be allowed by the governor, regardless of the information from the vacuum valve. (Under normal circumstances, low vacuum > shift at lower rpm, higher vacuum > raise the shift point.)

you may have a look at this thread for further info : https://www.ferrarichat.com/forum/threads/th400-governor-adjustment.620188/

 

Thanks guys!

 

Have been following this thread closely as I have been contemplating rebuilding the tranny. on my 78 400. The car already has a high stall speed Torque Converter, but recently has been slipping a bit. I decided to bring it over to Richard at Competizione & Sports Cars to have a look. As we were test driving, the tranny slipped badly and decided it was best to not continue driving. Left it with Richard and he will pull the tranny. Fortunately, we have one of the best transmission shops in the country nearby (Performance Automatics-PA). Once we pull the tranny and find out what is the issue, we will meet with PA to look at alternatives to best match the tranny to the power curve of the 400. Right now we think it may be a front bearing. When I drained the pan a few weeks ago, silver filings were evident. I then pulled the pan and the filter was totally clogged with non-metallic gray/silver filings. Probably aluminum or clutch material. I replaced the filter and she ran well for a while, then the high pitch and slipping reoccurred. Will be interesting to find out what is wrong, but more importantly how we can improve the TH 400.

 

Hello,

the first change I suggest is to get a new "low gear" set, (2.75/1.57).




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All set to take down the gear box for a full overhaul, new converter and shift kit later this month.

If I would like to go one step further and change gears to 2.75/1.57, would the gears from a TH350 fit the TH400? Where do you get the gear kit at decent prices? I'm in Europe.

 

I bought mine from TCI. Shipping is not an issue, DHL/Fedex/UPS.



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Yes the Raybestos kit and Transgo for the shift improver.

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This is what Performance Automatic uses as well, Raybestos and Transgo. Not sure if I saw that anyone commented on their results after changing the gears to 2.75/1.57. If so was this done in conjunction with a higher stall speed torque converter?

 

Hi,

I did see the planetary gear kit from TCI but it states TH350. Are the TH350 and TH400 the same?

They were also quite expensive with shipping to Europe and VAT so it is definitely of interest to hear if the mod worked out well with a higher stall converter.

I seem to have gathered the right stuff for the coming gearbox overhaul, full Raybestos kit, TransGo shift kit and a new 10" converter from TCI.

Is it recommended to change the sprag to the multiple roller type (34). If so should both be changed?

Thank you
//Rob

 

Any converter is a dramatic performance upgrade. Fully "rolerrizing" (4l80 sprag & a few other bits) the gearbox is a dramatic reliability upgrade.

The shift kit reduces the transition between gear changes so less stress on the friction band, but some serious "bang" on the rear axle, and probably highly demanding on the converter. I blew-up my PAE converter in a matter of weeks, and the pro-torque i subsequently bought and recently removed has some clear signs of wear on the pressure bearing that's against the gearbox input shaft.

So let's not forget that the original converter was ~12 inches, so if we want to pass the same amount of torques on a 10inch one we'd better invest in a proper one.