Looking for some first hand experience with the "Quaterbreed" as the kit is called. Replacing the BW trans with a GM 700R4 or TH350. I sent an email to John's Cars and surprisingly didn't get much help. St last not what I was looking for. My question is to how the car performs with the new gears. I've owned both a stock and V8 swapped XJ6 and the V8 was admittedly a much better driver. But I'm holding out hope that a new trans might give performance close to that of the lumped Jag. I'd prefer to run that glorious XK engine.

 

My recently acquired Series III was fitted with the GM T700 as part of a pro-rebuild 14 years ago. All I can tell you is the shifts are smooth and decisive, kickdown is right on command, and the XK really pulls - hard. Now I can't directly compare it with a standard 3sp BW trans in this model, but it is far and away superior to the standard trans in the much younger X300 I owned previously. This one feels alive and unrestricted. From all accounts plus my relatively brief experience living with it, I believe the T700 is the perfect mod / upgrade for the XK engine.

 

I've never heard of anyone being unhappy with the swap to a GM trans. Even the old TH350 3-speed is a good improvement over the BW66


Cheers
DD

 

Thanks Jagent, I saw your car earlier and hoped you would chime in. Wish I was closer and could go for a spin!

 

You would be most welcome, sadly the tyranny of distance can be very frustrating!

 

I've never done the Quarterbreed to my car because of one silly cosmetic detail: John's Cars does not provide a shifter indicator replacement. A silly detail for some, an important detail for me that was left out and that John's Cars has had plenty of years to develop and manufacture in order to supply his customers a complete, finished kit but never did. Sorry John, no sale.

Then you have the peripheral items like having to replace the starter, the driveshaft, and other items that are needed on top of the kit you purchase. Too much complication for my taste.

having said that, I am in agreement that the 4-speed GM 700R is an improvement over the original BW66 transmission, which isn't such a bad transmission either. It's just that we are never happy with what we have and we always want "new and improved".

if I could afford it, I would prefer to do the ZF (XJ-40) transmission conversion sold by GW Autos in the UK, because the ZF has an automatic setting and a "Sport" setting which allows you to shift like a manual transmission, so to speak. And yes, their kit supplies a replacement Shif Indicator for the center console. But the darn thing is way expensive as everything else in the UK. I guess you get what you pay for.

 

deleted - duplicate

 

Two points:


1. True, John isn't a fan of email ! But, I got lots of help in the past via the telephone and "old fashioned" FAX!!!


2. The XJ6 quadrant and the GM quadrant are not that far off. many just live with it just fine. However, a relatively easy fix is to swap in a tower from a V12 XJS. Solves the quadrant issue and the N?s and reverse lamp issue. My wuzza six has an XJS tower. Works nicely. When swapping it in, I fixed some other stuff in the console area.


Caveat, some including John don't think the XK engine has the suds to pull Od when the final ratio is 2.88. Others find it is just fine.


GM 700 or even 350 over the BW66 merely that progress thing.


And, while the ZF sounds attractive, service and availability in the USA???
Setting the kit aside. How much for a used or rebuilt ZF vs the same 350 or 700?


Oh, one can manual shift a GM. Or just start in 2 and leave it there.... The speedo and tach will leap. Oh, the gas guage as well.....


But, to each his own....


Carl

 

Carl,

Do you by any chance have a photo of the xjs tower installed????

 

Darren:


No, it is under the ski slope.


It looks almost exactly like the XJ6. It bolts right in using the same fasteners.


1. The detents are different to match GM shift positions.
2. A spacer on the front of the tower used on the XJ6 is replaced by another micro switch. Neutral start function.


3. A threaded bug is stamped in on the left side of the tower. The XJS reverse lamp switch goes here.


4. I expect David Boger could come up with a good one for a reasonable price.


Jose:


4. Different starter? That sounds odd. What and where? A really old Delco might fit in the Jag hole and bot pattern. Newer GM's are block mounted. Ask me, I have mastered the R&R!!!




Carl

 

I can't speak to the issue exactly as I'm still with my BW 12.

I did want to say something about John at John's Cars. As stated above, he is not an email person but he is generosity itself on the phone.

He really knows our cars well, like, really, really well, and is patient. I say this last as a somewhat novice Jaguar person and he has given me loads of help on the phone. I've also bought parts off him and found them excellent with quick delivery.

 

I did the swap back in 1994, GM 400 to GM 700R4, single piece aluminum drivshaft!

been fine,no problems,ever!
i also changed my final drive gear ratio to a 3.73, in overdrive it gives me a 2.60-1 ratio, nice slow RPMs, the 700 1st & 2nd gears give fantastic acceleration, and cruising is comfortable in OD.

i do believe an XK engine with an overdrive trans could not pull a 2.88 rear gear, even at highway speeds, you would have terrible MPG ,because the slightest speed increase, would open throttle to much, also just cruising you would you would use to much throttle, to keep up with traffic!

 

Shouldn't be a problem.

If the trans is operating properly it'll downshift from 4th to 3rd (or even 2nd if the road speed is low enough) easily and quickly when throttle opening and engine load dictate.....thus eliminating lugging.

Or the driver could manually select "3" thus eliminating 4th (OD) gear until conditions are appropriate to use it.

Cheers
DD

 

I've actually always wanted to install a ratchet-shifter. It would be great to be banging gears with that thing.

 

funny you ask , i do use a B&M rachet shifter with a custom made aluminum knob, more like a lever. works great, i also run a B&M shift kit in the 700, so it holds in each gear!

 

Yeah, when prepping for SMOG, I lock out OD. Get the engines to work and heat the cat!!!!


Ugh, Jaguar is up this year.. Hate that.... Some shops now up to &) bucks and more. gotta shop....


Carl.

 

TYPO" again. Seventy Dollars at some, more elsewhere.


CAVEAT, around here, beware of the small print in any adds.


Carl

 

First hand experience here. Swapped my 86 XJ6. First, Johns kit is fantastic to install, he's made all the mistakes and already sorted them (but for one). Step by step instructions, follow them and you'll have a blast.

OD and lugging issues were obvious and in my case came from the TV cable geometry. John sends a bracket to secure the cable housing iirc, but does not take into account the tv cable geometry. It must very precisely located on the throttle connection as close as 1/64 inch proper radius from the pivot, and the angle of the cable housing tangent to the throttle movement has to be perfect. Just connecting it to the jag stud resulted in about a 1/4 inch error and the cable angle was way off. Trans shifted into od at very low speeds and shifting pattern was just not like a th700 should be.
Spent a lot of time with a spare intake manifold and TB to make a bracket and a throttle connection that was as per GM (google, lots of info) and it works like a charm! ...Like it's supposed to. No issue with od at cruise, pretty effortless, in fact a fun part of driving this car is over 70mph. Picked up maybe 2 miles per gallon, but biggest thing is it's much quicker driving in town. 100% improvement, what Jag should have used in these cars in the first place!