400i automatic transmission

After having cured some small mechanical and electrical problems, I do start to gain some driving experience with my new car. It is probably normal that acceleration with standing start is not very impressive but what I would expect is a good response with "kickdown" at cruising speed. According to the manual it should shift into 1st at road speed below 70 kmh (45mph) which it never does (lever position D). It changes however to 2nd which may not be triggered by the kickdown micro switch but by the manifold pressure.
The micro switch as such is working (it is set to close before the throttle is fully open) but how do I check the function of the automatic transmission itself? Unfortunately my workshop manual is giving information for the 5 speed gearbox only. Not a single sentence about the automatic transmission. Is there any literature about how to test and how to adjust the automatic?
What kind of experience do other owners have with the kickdown function?

Peter

 

Peter

its a GM300 gearbox, it's also used in older Range Rover's, Rolls Royce's, Jaguars as well as dozens of US cars.....all of whom have far better manuals and support than Ferrari, I'd suggest you hunt down a copy of the GM workshop manual (should be out there on the net somewhere)

You are right They should have a very good pickup when the box kicks down

 

Having owned and driven my 1980 400i for ten years, It is my years of inexperience, that when it comes to transmissions..spend afew dollars at the most repudable transmission shop in your are ... usually the problem is minor,and the trouble that you will get into by trying to "save" is far more serious than whatever problem you may or may not actually have. Even at total rebuild including a new torque converter is only $850-$1000....and takes about two days with an appointment.....if you ever have it rebuilt, have the shop install a mild street shift kit,,$50 more..it will trasform the out of the hole performance..and you'll have no more performance *****ing... Never ever let your mechanic work on your tranny!!!...The GM manual is available for $15-$20, as GM made billions of them..just like little fish eggs...the black or brown micro switch on the engine is no mystery either...just take it into an electronic supply store..its' a very very common switch used in many industries..$5-$10..Radio Shack won't have this one....also.. the ONLY thing unique about this tranny..so dont' anyone snow you on this one is the european bell housing...frusrustating yourself about keeping the 400's "original o
is foolish, usless,unnecessarily expensive because the value is just not there..so just fix it and drive the thing..enjoy...Jacques...over...

 

Peter,
At what altitude do you normally operate the car?

Tony

 

Tony,

so far, I was driving the car at altitudes between 300 and 600 meters.

in the meantime I have "tested" the kickdown solenoid in the sense that I can hear it clicking when operating the microswitch which of course is no proof that it is properly influencing the hydraulic control of the transmission.

I also wonder how the vacuum system is working. it looks like there is a straight through connection from the vacuum pump to the automatic transmission (from right to left in the enclosed picture) via the "control dvice" in the centre. Can any one give me an explanation how this is working? From other cars I know that the manifold pressure (vacuum) is directly used to control the speed change of the transmission.

Jacques,

I will try to receive a service manual from GM (Switzerland) - if they are willing to sell one for private use.

Thanks, Peter
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My 400i rarely, if ever, downshifts on its own when I want it to. Keep your hand on the shifter, and do a little manual shifting, and you should be fine.

Free, too!

 

Actually, There isn't even a "European bellhousing". There is an aluminum Ferrari-to-Chevrolet adapter plate between the engine and the totally normal ( except the tail shaft housing ) TH400 trans.

At least on my '84 400i.

 

Peter,
The reason for the altitude question is: On my 1984 12 cyl xj-s Jaguar, a similar set up ie. big v-12 with the same transmission, The car is very reluctant to down shift at my altitude 3800 to 4200 feet, but is totally transformed at sea level. You might try advancing the ignition timing about 4 degrees (listen for pinging - pinging is bad for the engine). The engine should tolerate a modest timing advance and at least on my v-12 Jag, the increase improved power and improved the willingness of the tranny to down shift. On the Jag v-12, the vacuum line is a direct rout from the intake manifold to the tranny. It appears that you have a valve that is vacuum actuated to supply vacuum from the vacuum pump. One to many things to go wrong in my opinion. Perhaps you could make a direct manifold to transmission connection to see if this helps.

Good Luck,
Tony

Ps. The ignition timing may be at present set retarded as this often helps pass emissions testing.

DON'T LET IT PING

 

I wonder if a newer 4 speed GM 700R4 would fit in its place?

 

It would be great if it did fit but the enclosed drive shaft of the 400i is very different than the universal joints that connect to the later 4-speed GM automatics. That's why the TH-400 has a Ferrari only tail shaft housing.

Al

 

Yes - but would that ferrari only tail shaft fit on the back of another GM bell housing - say a 4 speed 4L60, etc.? That is the million dollar question...

Thanks,

Alex

 

I'm sure someone with the right equipment and skill could get a current GM 4 speed auto to replace the TH400 a 400A/400iA/412A but it wouldn't be easy. There are issues that come quickly to mind:
1. The bell housing mount to the engine. I'm sure an adapter plate could be made.
2. The tailshaft and tailshaft housing. The 400 has a special Ferrari casting. It's not clear in the photos if the bolt pattern is the same but there would be length issues since each GM transmission appears to be a different length.
3. The 4 speed autos are made to be controlled by computers (which the 400s are fortunately lacking!). I believe there is technology on the market that addresses this issue (created for the Street Rod market)
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Hey - we are getting somewhere. No need to deal with a computerized 4 speed trans. While the 4l60e is an electronic 4 speed, the 4L60 is a non-computer controlled 4speed. This seems like the trans to focus on for a swap.

The bell housing mount to the engine is the same for a TH400 (in the car) and a 4L60 (at least according to the diagram you posted).

The tailshaft seems to me to be the only real issue. The million dollar question is will the ferrari tailshaft casting bolt to a 4L60 - that is, is the bolt pattern on a 4L60 the same as on a th400...anyone know? I am NOT worried about the lenght - shortening the torque tube and drive shaft to accomodate the longer trans would be a no brainer. Only other issue I could imagine is shift linkage and tranny tunnel room - any ideas on those either?

A

 

I did some measuring when I was considering swaping in a doug nash 5-speed trans. The output spline is the same as the standard GM TH400 ( also same as the DN 5-speed ). It would take a little work with a plasma torch and a TIG welder to mount an adapter ring for the enclosed drive shaft. But it is not a huge job.

The bellhousing adapter that comes with the 400i matches the standard Chevy style GM pattern.

If I can figure out the clutch setup I may still do the swap.

 

Sure would be nice to have an extra gear. I think I'll take a little drive over to the local tranny shop and see what they have to say.

 

Pete,
I had a Jag XJS v12 with a GM 400automatic 3 speed, and I believe it's the same transmission.
I had the same problems, and that vacuum line that is coming off the vacuum valve goes to the transmission, where there is another type of vacuum valve on the right side of the transmission. That valve controls upshift speed, and could effect the downshifts as well. The valve that sits on the side of the transmission can be adjusted (with a tiny flathead screwdriver) just remove the tube that connects to the valve, and you can adjust it from there. Now if you get fluid out of the the valve when you pull the vacuum tube off, replace the valve, it's gone bad, and is quite common. You can probably get a replacement at Napa for about $20(that was five years ago).
Ultimately my transmission went bad because I was lazy and didn't have someone else look at it deeper, and second gear started slipping and would only rev up to 2 grand then shift into third, then it just wouldn't up shift anymore. Even then you can get the trans rebuilt for 1200-1500 dollars and be done with it. Now there are things that can be checked inside the trans, like the bands, or the transmission pump. The pump I think can be replaced, and the bands I think can be adjusted. After I had the trans rebuilt, the car was much quicker in shifting and the downshift from 3rd to 2nd at 70 was pretty impressive.

 

Actually it is a TH400

There is a flexplate between the tranny that is Fcar unique

.

 

Hi James,

Thanks for your comments. In the meantime I have found the reason for the missing downshift. It was simply the micro switch on the accelerator lever with a periodical malfunction. After replacing it, the transmission works absolutely fine as expected.

Peter