How much HP/Torque do you think you could put through a stock '82 XJS tranny/diff without destroying them? Is 350HP to the rear tires an unreasonable figure? I've got... a Chevy 305 in it (I know, I know) and I'm thinking about doing some work to it. Well, a lot of work to it. Actually, replacing it with a 350.

Thanks! Merry Christmas!

 

Matjohns,

That Diff will take a lot of HP & torque. I had one hooked up to a 454 Chev Big Block and it did very well. Can't speak to the tranny as I was unaware of a way to mate it to Chev and so I never did it.

If, however, you have somehow figured a way to mate the Chev to the Jag tranny, and the Jag tranny is the TH400 -- then my guess is it will hold any small block you can throw at it.

 

I agree,Years ago I had a 75 Monte Carlo with a 454 and the tranny was a TH400

 

like said,, it will handle a lot, diff is a DANA 44 powerlok,, and just use a GM t400 tranny, that bolts to the chevy engine.

but never put slicks on a jag rear suspension , its just made for good road drivin, slicks will tear the whole rear subframe out of vehicle.

 

Right on, I figured the GM tranny would hold up to some serious strain, and I've further heard that the XJS rear end is very stout. I figured that the whole assembly could handle small block power, but it definitely good to hear that it can take big block power too (454, nice).

Word up on the slicks. I'm planning on making this lass powerful, comfortable and safe. No drag slicks for her. I'd rather have good road tires and glue myself to the asphalt.

Thanks!

 

As said.

Consider the Bentley TurboR 2500+kg, V8 Turbo charged, big **** car by any understanding, through a TH400 3 speed trans, then a TH400 4 speed for later years.

Do a google and I reckon you will be amazed at the vehicles using that trans including cars, trucks, buses, military vehicles etc.

 

Regarding the TH400 trans I'll just add that you'll want to firm up the shifts a bit to help ensure a long life. In most applications, including Jags, they are set up to give a nice, easy, s-o-f-t shift......with the clutch plates taking a beating.

So, while it isn't easy to break a 400 it's fairly easy to wear one out, if you get what I mean.

Cheers
DD

 

Dont build a t400, do a 4l80e, its a t400 with overdrive and you can tune shift points and firmness. Go the companies like b&m, tci, etc for a complete plug n play. And dont waste your time on a 350, either do a ls swap, or do a 383(400 crank in a 350 block, .030 over) the extra displacement from the longer stroke gives alot more torque, way more than the extra 30cid would make you think. And those kits and crate engine are cheap today(comparativly speaking)
if my drive train ever gives up the ghost, ill do a complete ls swap with ecu, engine and trans. That way it will still pass state insp since the state computor will read the obdii connector and ecu. Then this car will actually have some performance cause other than mpg and comfort, ide rather drive the suburban or nissan with alot more hp

 

Just be prepared for some creative sledge hammering to get the 4L80E into the trans tunnel of an early XJS :-)




Cheers
DD

 

Lol yeah but you only do that once and it still fits, only a little bigger than a t400
and i would do the all aluminum ls, probobly come in at about the same weight. But then would have to change morethan you already have where a sbc is still a drop in, and i believe scott shafiroff and a ferw others are still building small block chevy strokers that displace 454cid in a sbc size

 

My last project hotrod was a '74 Maverick, and I'll tell you, sledgehammering was not something I was afraid to do it. The thought of putting a hammer into my Jag however, makes me cry! Maybe I'll stick with rebuilding the TH400...

 

Then put a gear venders overdrive unit behind it. Not only will you get overdrive to make it de3cent on the higway, but you can gear split with it turning the 3 speed auto effectively into a 6spd. Plus its about the size of a coffee can on the end of the trans(replaces the output housing), is bullet proof(people run then behind engines putting out over 1000hp) and you onlly need to shorten the drive shaft. And if youre still using the 2 piece, now would be a great time to get a new 1 piece and ditch the carrier

 

The thought of an XJS with a Chevy 305 in it makes me cry!

 

I know me too, especially when a big block chevy fits just as well

 

The "gear Venders overdrive" is very interesting.
Where might I find more info about it?
I'm restoring an 89 series 3 VDP (the Canadian version with the 5.3)
Much appreciate it.

 

http://www.gearvendors.com

 

Hi Brutal,
Thank you for the great info.
I was contemplating installing 5-speed tranny from the Driven Man but this may be a great alternative.
Cheers
Peter

 

Well if you do they can either make an adapter for that or have 1 already. This still lets you gear split (10spd) and double overdrive

 

That would be an interesting conversation piece
Will look into that.
Cheers

 

For whatever is worth, I'm putting 350HP on a rearend originally intended for a 219HP power plant. My 1994 XJS has 130 HP worth of nitrous over the stock rated 219 HP. It has the 4.0L straight six AJ6 engine with a ZF 4speed/auto and 3.54:1 final drive ratio. The math puts it a 350 FWHP and the rear end appears to be absolutely fine with that power, even when at the more aggressive settings of the N2O progressive controller it can easily push the 4000 Lb convertible to 60mph in 5.2 sec. which I actually timed back when my jets were still only 100HP jets, not 130. -- I guess that all those Jaguar rearends that I see on hot rods at car shows should make for peace of mind for those putting them to test with serious torque power plants. The last one I saw the other day even had an XJ6 entire front end, as well as the rear end. What I'm not sure of, however, is whether they manipulate the actual differential set up, or if they leave it alone, all Jag.