Curious to know if there's an alternative auto box to the standard 3 speed auto box in my 4.2 series 3.

There's nothing particularly wrong with it (although I'll need to whip it out for a freshen up at some point) but I'm used to 4 speed autos and the 3 speed feels like it's missing a cog

 

Indeed, there is. But, I only know of a USA source. Johnscars, Jaguar lane, Fort Worth, Texas. I think his website is brokenkitty. He has a kit for GM TH350 and related. Although he isn't enamored of the OD behind the DOHC 6, others have used his kit to fit the 700R that is a 4 speed. Most seem pleased.


John's concern is the lack of enough torque to pull a very high rear ratio. Here the cars usually have a 2.88. So, adding a .70 OD is high!!!


My car has the stock. 2.88. And the 4L60E transmission having a .70 OD. It handles it just fine. But it has the added "suds" of the LT1 V8!!!l


I'd say it is well worth looking into.


Whether John's ships overseas is unknown to me.


Carl

 

My car (with stock 4.2) is running the GM T700 4 speed. Strong right across the band, and excellent torque low down. Sits on 1700 rpm cruising at 100kph. Would highly recommend this box.

 

in the UK, if you have the money, there is G Whitehouse autos who install a ZF transmission from the XJ-40 in earlier cars.

:: G. Whitehouse Autos Ltd ::

 

Are you running a 2.88 rear end?

 

Mine runs 3.31 which was fitted as stock in our market.

I believe 2.88 is a North American spec but I'm unsure if it also applies elsewhere. My understanding is that ROW models had 3.31, and (I think) 3.07 pre 1982. I may be wrong on some of this...

 

My US spec Series II has 3.31 gears. I've sort of gleaned in here that 2.88 was for Series III as most S3 owners seem to have 2.88s.
(';')

 

I wondered! Was hoping you were getting that satisfying performance with a 2.88 like mine, despite John's Cars's recommendation otherwise for the 700.

 

I believe that's so in the U.S., Elinor. It's possible the S2 had 3.31 in all markets.

 

Yep, fair point.

The T700 conversion on S3's is popular here, likely due to the more suitable back end ratio. Same should also apply in the UK.

The other benefit is that the 700 is compatible with the existing shift selector/quadrant, although the lever doesn't align perfectly with each R,D,N positions. Each one is off by about 3-4 mm. Not hard to live with.

 

I just go for the second stop for each gear and that's the one.
(';')

 

Or, swap in a shift tower from a V12 powered XJS. As they used a GM trans,
the quadrant detents match.


I did that to my car. slick.


Carl

 

Early Series III XJ6s had a 3.07 ratio. I think the 2.88 became standard issue 1981-ish.


On paper, and by conventional wisdom, the 2.88 combined with the OD fourth gear should be a problem but I've never really heard any complaints.

If the engine starts to lug, the trans downshifts to 3rd gear, as designed. No problem.....except for it might be downing shifting more frequently than some might be accustomed to if they had a more favorable weight/power ratio...and/or a more suitable diff ratio.

Cheers
DD

 

Cheers everyone.

What was the T700R fitted to originally ?

 

I believe it was first used by GM in various cars and trucks from the early '80's. Mine was a new unit fitted as part of a full rebuild 14 yrs ago.

 

Mine was new in 1986 at the time of conversion.
(';')

 

Right, and typical of GM transmissions, it took 3-4 years to work out all the bugs. The early versions were terrible. Circa 1986-87 they were pretty well sorted.

If looking for a used 700 you not only want a later version with the updates but must also consider what it was originally used in. There were at least a couple dozen sub-variants of the 700 that were 'tuned' to specific applications and even with different bell housing bolt patterns and internal parts.

Tons of info on the www.

Cheers
DD

 

Cheers everyone.


I dont suppose anyone knows of a resto / how to / technical type link on a forum or something of someone who has done one of these conversions ?

 

John's Cars will sell you the complete instructions, but the shifter indicator in your 1984 will not match the new T700 transmission shift points, that is the one and only reason I have never done the conversion to my 1984; if the so-called "kit" is not complete, why bother?

you will also need to change the starter and the driveshaft, too much complication, that is why I prefer G Whitehouse because they have the conversion complete, but their price is un-affordable.

 

Jose:


1. Change the starter? Why"


2. Drive shaft. Yes, front Flange to slip yoke, mebbe. Not sure. Away with the
middle joint. Great idea. Away with the over engineered Jag trans mount, even better.


3. Even with a slight mismatch of quadrant detents, it does work;


4; Swapping in an XJS shift tower fixes that perfectly.


5. 4th gear means a lot.


6. Using a 2.88 was a crutch to get the final ratio with a 3 speed auto.


Dollars, yep!!!


Carl