Gear box swap/upgrade in 400 auto

Dear all,

Has anybody heard of anybody doing a gearbox upgrade from the original TH400 3 speed to a TH700 4 speed gear box in a 400 series car? -Or similar?

The TH 400 is not a very nice gearbox to start with and the fact that that is only has 3 forward gears feels very outdated. A TH700 is about the same (same bolt pattern) with an overdrive to give 4 forward gears. -Or one could use the 4L60/4L80 (not the E version as it needs a computer).

-Which brings us to the most interesting bolt-on upgrade the 6L80, a six speed auto in the same casing as the 4L80 and probably a pretty straight swap to a TH400.

I know it's not original and that a manual conversion would be an alternative but it comes with lots of changes (pedals, console, mounts, clutch and so on). Not even mentioning finding a complete set (without buying a donor car).

But.....would it not be nice with a manually (paddle) shifted 6 speed in a 400?? Auto shifting for the wife go shopping and manual for me having fun…

http://www.tciauto.com/Products/6x/

Ideas?


//Robert

 

Robert,

Welcome aboard!

I believe John's Cars www.johnscars.com does various GM transmission conversions and rebuilds for Jaguars. They would probobly give you good information on the GM tranny upgrade.

Regards,

Art S.

 

Art,

Thank you for the link. I did see them from an older thread. I think it should be even easier on the 400 since the original is a GM box mounted on a Ferrari to GM bolt pattern adapter. This means that many GM boxes would be just to bolt up.

I have seen some talking about that the tail end of the box was special for Ferrari, but I thought that this was a GM piece since they made at least three different lenghts of the drive shaft end. Can anyone please confirm if the drive shaft end on the TH400 indeed is a Ferrari made piece? Or Ferrari special order?

The idea with the 6X box is that since the bolt patterns are the same it should be more or less a straight bolt on. I understand that the mounts may be different and that the drive shaft and the torque tube may have to be shortened, but still pretty straight forward.

The neat thing with the TCI 6X is that it gives you 6 forward gears that you can shift completely manual with the gear lever (only 1-4) or with paddles behind the stearing wheel. They do sell a kit which contains a stand alone computer so it should be minimal changes to plumbing and wiring.

The car would also look completely stock on the outside and one could even keep the original gear shifter.

A complete kit seems to run arround the 5.5k$ mark which is pretty expensive but it would probably completely transform the driving experience. Don't you think?

//Robert

 

The 4L80E trans. doesn't appear to be a straight bolt-on.

Kit priced out @ $6K.
http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=TC&Product_Code=271600P&Category_Code=
The lifetime warranty of the 4L80E is 'huge', though I'd comb through the fine print.

1st Pic: TH400
2nd Pic: 4L80E
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The Ferrari uses a torque tube and that is a Ferrari part and is the hang up. It is not just a case of changing yokes on a drive shaft.

 

Hi,

Thank you for quick replys. I do think it is a reasonable bolt-up.

http://www.rowand.net/shop/tech/automaticoverdrivetransmissionswap.htm

They do have different diffrent physical packages but many things seem to be the same. Please check the above web page for more details. Lot's more !

The yokes seem to be interchangable to a degree so that does not seem to be a big problem. A potential problem may be that that the 4L80 may be shorter! But that is not likely.

I will talk to my gearbox specialist to see if they can undertake a swap.

Summit racing is selling the kit for 5.8k$
http://www.summitracing.com/parts/TCI-271600P/

Any thoughts?

//Robert

 

Hold out and find a 5 speed.

 

tail is a Ferrari unit to my knowledge. Here are some pics of my gbox
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Plus One.
Buy the 400 you want, it is cheaper than building the 400 you want.

The diff. is the rear engine mount. The drive shaft is not an issue, it is the torque tube around the drive shaft that connects the trans. to the diff. that will take some fitting.
Anything can be done with enough time and money thrown at it, but is it worth it?

 

Fritz knows what he is talking about......

Cost to convert a 400i into the car you want = thousands and you get a car that every future buyer says, "somebody has modified it and who knows what else was done."

Cost to buy a nice 5-speed (if you can find one) = 35k to 40k+

Its a no brainer, for the cost of a nice F250 crew-cab pickup truck you can buy a 5-speed.

 

Do a little research on the paddle-shifter as some are better than others. I seem to recall that this one: http://twistmachine.com/shopping/index.php?main_page=index&cPath=1 was the better unit out there, but I could be wrong. A little research on Lateral-g.net should turn up a bunch of information on the various offerings.

Shiny Side Up!
Bill

 

The enclosed driveshaft will be the biggest hurdle to clear.
I'm near certain the tailpiece is Ferrari, nothing a TH400(which by the way is probably the finest three speed autobox ever made) ever appeared in had an enclosed driveshaft.
A lot of work to swap anything with more forward gears and it'll still be slushbox.
While 3 speeds is woefully inadequate for spirited driving the shifts are easily improved with a fifty dollar shift kit, or simply removing a check ball or two from the valve body.

 

True, but as some of the newer autos are based on the TH400, there are a fair deal of parts that will interchange. A good trans shop may very well be able to adapt the trans to the enclosed driveshaft.

Shiny Side Up!
Bill

 

I had a client years ago that was considering such a conversion. It really needs to be done in conjunction with a change in differential gearing. That means getting a diff from a 5 speed car or buying a ring and pinion. The cost of a ring and pinion is not far from the price for a complete running 400. Rules that out. Finding a diff from a 5 speed car will not be easy or cheap but I would want to cross that hurdle before investing a penny in any other step of the project because the entire project revolves around that success.

 

Is this because the overdrive ratio is more in line w/5th gear? Or is it to keep the RPM range smaller between gears?

A 6 speed auto trans w/auto diff would get you off the line & accel thru the gears quicker than the TH400 & a higher top end to boot!

 

Car would never have the HP to drive 6th or even 5th with the auto gear ratio. No point in having 2 useless gears. The whole point in having a 4, 5, or 6 speed is to get a gear that will get that slug underway and that will not happen with the auto gear ratio, it is too tall but they were stuck with it when they chose a 3 speed trans.

 

Thanks for all the input.

A couple of observations.

I agree that it probably take some work to get the torque tube right. The rest should not be impossible.

The reason for me to do the change on my car as opposed to buy a 5-speed is that mine has only covered 30k miles from new and I'm the second owner. The second reason is that it is a Straman convertible which kind of limits the alternatives.

On the gear issue I don't totally agree. The 6 speed has a 5th gear which is 1:1, i.e. the same as the original 400 box. This means that there is no horse power issue as the gearing on 5th will be exactly the same as in third gear with the TH400. The 6th gear is a overdrive with 1:0,75. Mine does above 3000rpms at 60mph so reducing that with 25% at plain highway cruising would be nice. Horsepower cannot be an issue either as the engine would stay above 2500 rpm’s with limited load.

This means that the 6 speed gives better options to keep the engine within power band up to 5th gear and a possibility to lower the rpms with 25% when cruising on the highway.

The rear axle differential gearing should not be an issue either because the 5th gear is the same as the 3rd gear on TH400, 1:1. The only difference is 5 gears instead of 3 up to 1:1 and an additional 6th overdrive to reduce rpms 25%.

I also think a programmable 6L80 gearbox should change gear quicker and also give the possibility to use lock-up for most gears.

Surely that must transform the driving experience.

Thoughts?

//Robert

 

I, too, have difficulty believing this when 5th gear (6 sp. auto) has the same output spline shaft ratio of 3rd gear in the TH400, i.e., 1:1. And 3rd gear / auto has basically the same final drive ratio as 5th gear / manual...1:3.4166 vs 1:3.4178. The 0-60 mph & 1/4 mi. times are off a little w/the auto trans (6.9/7.1 sec. & 14.8/15.6 sec.) but they appear to still be able to reach top end w/o difficulty. Sure, these 'slugs' (400i's I'm assuming) are 700 lbs. over & 50 HP short of the 512 but its not an unusual occurence for them to mark 130-140 on the ticker w/o ever exceeding 1/2 throttle. And they don't waver one bit @ top end. A true GTer!
I'd rather drop $$ for superchargers than a donor car for its rear end.
I'm curious of other auto trans owners' experience with pull /throttle effort.
Anybody have HP / Torque curve charts on these babies??

 

Well, that answers that question. You are sooo lucky!

 

For only $1650.! Hurry, only 17 days left.

http://cgi.ebay.com/ebaymotors/FERRARI-400-V12-DIFF-DIFFERENTIAL-10-43-RATIO-4-30-/380235718659?cmd=ViewItem&pt=Motors_Car_Truck_Parts_Accessories&hash=item5887d0a003

 

4l80 tranny is basicly a turbo 400 with overdrive,4l60 is a turbo 350 with overdrive,,adding an e to it adds electronic controls,,there are stand-alone computers for these and there are paddle shifter set-ups avalible too,gm also makes a 6-spd auto [its used on new caddys and camaros / corvettes] and vettes have paddle shifters,,as for the tail shaft part turbo 400 and 4l80 trannys take the same adapters to 4x4 transfer cases so your ferrari parts should work,there are also companys that can make output shafts any splines and lengths

 

Somehow I feel that, by the time one is finished with all of these mods, you still have a 400i auto with a story and an all in cost that probably is not much below where some of the early 456's are trading for these days. Except that the 400i will still take 7 seconds to get to 60 mph, which is not fast these days, and the 456 has much better performance overall.

Even though they are fewer and harder to find, a good 5 speed will cost less and be more fun in my VHO.

It is probably an interesting engineering exercise, but not one that makes financial sense.

 

Thank you for all the input.

A 456 would be nice but there were even fever convertibles done of them (again Straman built, like mine).

Part of the fun with my 400 is that it is a convertible and that also limits the need for speed resources. Another limiting factor is the weight, it’s way to heavy to be a mover.

And the 456 is not really a fast car either. I built and used to run a supercharged Cosworth powered TVR with 550 Nm rear wheel torque in 930 kg car so most of the stuff out of Maranello, short of the supercars, is fairly slow up to 200km/h....

And I’m pretty happy with an auto box with the usage of the car. We use it on nice days and only for road use. Having raced a few years back in the dark ages, putting the 400 (and most of the older cars) on the track is not really my thing. When it comes to road use you always get stuck in traffic or find yourselves in endless sequences of stop-and-go du to traffic lights and/or crossing roads. Hence an auto box that let’s you use gears within the power-band, which the 3-speed TH400 does not, combined with being able to shift manually should suit me just fine.

The trick is not really the paddle shifter but to be able to keep the engine within the power-band and to manually shift combined with running full auto on my way to Stop&Shop…

On the issue GM 6-speed from Corvettes and a like it is much more difficult. These boxes have half of the electronics in the box and half of the electronics in the electronics box in the car. So far no one seems to have been able to make a stand alone programmable controller for usage with non computerized engines. I think that part of the reason is that the box communicates trough a CAN-bus and requires a lot of sensor data that does not exist on a non computerized engine. I have swept the net several times to see if anybody has been able to mate these new boxes with old engines. Sure, many have been mounted in old cars but always with a modern engine. If anyone else has seen anything different I would appreciate an update.

Unless someone comes up with a viable alternative I’m probably going to order the TCI 6-speed after the summer to have all installed and ready to go next summer.

//Robert

 

I think it could be a special car (low miles, convertible, yours, etc) and it has to be MUCH more enjoyable with 3 more ratios. Of course a gated shft C6 6M transaxle would be more my style.

But... it's your car and I think it could be a cool mod that could be reversible in the (enormously unlikely) event that 400s grow to Lusso money...

Life is short.

Post LOTS of pics please-

 

Join www.later-g.net and post there concerning the stand alone. If it's available, someone there will know about it.

Shiny Side Up!
Bill