Can the TH400 be converted to a TH700 (with Overdrive) in the existing bellhousing? Seems like Overdrive would dramatically improve the gas mileage of these cars without affecting all of their other road worthy features. Thanks,

 

Nope!

Two entirely different transmission families.

The is an OD version of the old 400: the 4L80E. Is a big mama, electronically controlled. Jaguar used them behind the 6.0 V12 and the XJR/6. But, a 400 cannot be converted into a 4L80E, either. Different case.

Cheers
DD

 

The bell housing will be the issue, you will need an adapter. I know that kits are available if you want to tackle it. I

 

Dellow have an adapter kit for jaguar V12 to T700 transmission. $450 aust dollars.

 

Thanks for the quick replies.
Throw another one into the 'Good Idea fairy' trash can. Not worth the effort to me at this point. Just focused on getting everything serviced and operating correctly for worry free fun driving.

 

As a side note, the bolt pattern of the 5.3 V12 and the 6.0 is not the same, so a 6.0 version of the 4L80e will not bolt to an earlier 5.3 to replace the TH400.

 

From what I understand the TH700 is basically an overdrive version of the TH350 so it's not got a lot in common with the TH400.

 

What else do you have to do to make the T700 work, Baxtor?

 

From the John's Cars website, here are a list of parts needed. Also, you will need a shortned driveshaft.Your V12 Quarterbreed kit features:

• block to transmission adaptor
• crankshaft/torque convertor adapters
• transmission crossmember and mount
• flywheel/convertor adaptor
• throttle pressure hookup
• shifter cable bracket and linkage
• speedometer necessities
• nuts, bolts, hardware
• Lock-It™ for the torque convertor
• 100% bolt-in, no welding (XJ models).
• freight paid in the continental USA
• my infamous instructions!

ROb

 

There was a thread here very recently describing the process.
https://www.jaguarforums.com/forum/x...s-cars-234770/

 

Thanks, I had not realised that XJeffs conversion was to the T700.

 

There isn't actually a transmission called a T700, that may be part of the confusion. It's correct name is the 700R4, then became the 4L60 and later when electronic controls were added became the 4L60e.

 

I suspect the "T700" comes indirectly from nomenclature commonly used by GM prior to the introduction of the 700R4.

For a long time GM marketed their transmission as "Turbo Hydramatic". You had the Turbo Hydramatic 400, the Turbo Hydramatic 350, the Turbo Hydramatic 125, and so forth. It become common to abbreviate these as TH400, TH350. TH125, etc.

Somehow or the other the "TH" was shortened, by some, yet again to simply "T".

By the time the 700R4 was introduced I recall that GM had stopped using the "Turbo Hydramatic" description...which probably coincided with the decision to change the entire system of designations, where, for example, the TH400 became the 3L80.

Cheers
DD

 

it is not 100% bolt in. Lots of cutting, grinding, and tunnel hammering. See my link that jagboi referenced. It is a great conversion, the kit is good, instuctions are a lot good, a little frustrating, short on illustrations and wrong sometimes. I have a short in the lockup circuit on the high side of the solenoid and have some sticking injectors and fuel tank crud to sort through to truly enjoy it.