Could my wedge have a 4.20 rear end?
Could my wedge have a 4.20 rear end?
Author
Discussion

tr7andtvr

Original Poster:

73 posts

232 months

Tuesday 15th September 2009
quotequote all
In 4th (1.0) at 3000 rpm with a 245/45/17 tire I am doing 75 mph. It was my understanding that all US 280i would have a 3.07 rear.....

grahamw48

9,944 posts

268 months

Tuesday 15th September 2009
quotequote all
The most common (or 'standard') diff ratio was 3.54:1 on both the 280s and the V8s...would have thought they'd have fitted a lower ratio if anything to the US
cars, to allow for the reduced bhp.

Naturally your much bigger wheels will give a higher ratio, even allowing for the lower profile tyres.

Just for comparison, my 400SE with 225/50 x 15 tyres and 3.54 diff gave 21.33 mph/1000 revs in 4th, according to the rolling road printout.

tr7andtvr

Original Poster:

73 posts

232 months

Wednesday 16th September 2009
quotequote all
I checked it with GPS and I am at 74... So that's about 18 per 1000. With the bigger tire, I would be going faster than stock if I had the 3.54.

grahamw48

9,944 posts

268 months

Wednesday 16th September 2009
quotequote all
Maybe I'm a bit thick, but at a 1:1 ratio (4th being a direct gear) 3,000 rpm at 75mph divided by 3 gives 25mph per 1,000 revs ...pretty high. scratchchin

rev-erend

21,623 posts

314 months

Wednesday 16th September 2009
quotequote all
There's a gearspeed calculator here :

http://www.gearboxman.co.uk/info.html


tr7andtvr

Original Poster:

73 posts

232 months

Wednesday 16th September 2009
quotequote all
I used a calculator like that to come up with the 4.20... It too takes into acount tire size, rpm, trans gears ratios, and rear end ratio. Did jag make a 4.20 rear? And how did it get in my car, could it have came with one?

rev-erend

21,623 posts

314 months

Wednesday 16th September 2009
quotequote all
In this thread at the bottom - someone mentions available axle ratio's

http://www.pistonheads.co.uk/gassing/topic.asp?h=0...


grahamw48

9,944 posts

268 months

Wednesday 16th September 2009
quotequote all
There was a Jaguar/Daimler 2.8 produced in the seventies, available in manual and auto. I used to own one...slow as hell, so I soon replaced with a 4.2. hehe

They were fitted with much lower axle ratios than the 4.2s and V12s, to give them a chance of gaining some inertia with their paltrey 140bhp and 3,600lb weight.

The V12s came with up to 2.88:1 diffs, as mentioned in the other thread.

Jag back ends were very popular with the street rodding/drag racing boys, so more info may be available on their sites.

heightswitch

6,322 posts

280 months

Wednesday 16th September 2009
quotequote all
grahamw48 said:
There was a Jaguar/Daimler 2.8 produced in the seventies, available in manual and auto. I used to own one...slow as hell, so I soon replaced with a 4.2. hehe

They were fitted with much lower axle ratios than the 4.2s and V12s, to give them a chance of gaining some inertia with their paltrey 140bhp and 3,600lb weight.

The V12s came with up to 2.88:1 diffs, as mentioned in the other thread.

Jag back ends were very popular with the street rodding/drag racing boys, so more info may be available on their sites.
4HU's were available in 2.88 very common,3.07 original griffith, 3.31 (sure this was most common in wedges and 3000M 3.54 Not so common and pretty hard to get these days due to cobra builders buying them, 3.77 (Rare) 4.1 (special)

instead of buggering about with calculators. jack your car up and mark the diff case and flange and mark your wheel with tip ex. Turn the wheel slowly through 1 revolution and count the number of times the front flange rotates past your white marker on the diff case.

N.


Edited by heightswitch on Wednesday 16th September 19:37

grahamw48

9,944 posts

268 months

Wednesday 16th September 2009
quotequote all
I was trying to remember the 'practical' way to calculate it...but couldn't. biggrin

In the 280/350 handbook it gives the ratio as 3.54:1, but of course nothing was really 'standard' on the cars I suppose.

Personally I'd just go for the bigger wheels. By keeping the old ones you still have a choice of ratios too, whether for drag racing or motorway cruising.

That's what I did with one of my Lotus Sevens; a pair of 13s and a pair of 14s.

Not sure what the implications are insurance-wise. They'll use any excuse to get out of paying.

heightswitch

6,322 posts

280 months

Wednesday 16th September 2009
quotequote all
grahamw48 said:
I was trying to remember the 'practical' way to calculate it...but couldn't. biggrin

In the 280/350 handbook it gives the ratio as 3.54:1, but of course nothing was really 'standard' on the cars I suppose.

Personally I'd just go for the bigger wheels. By keeping the old ones you still have a choice of ratios too, whether for drag racing or motorway cruising.

That's what I did with one of my Lotus Sevens; a pair of 13s and a pair of 14s.

Not sure what the implications are insurance-wise. They'll use any excuse to get out of paying.
Wedges may have been 3.54. they were common but a bit harder to get these days.
a 4.2 will be aesy to identify since the car will likely as not only do about 80mph flat outhehe


Edited by heightswitch on Wednesday 16th September 19:41

Brap_Brap

753 posts

239 months

Wednesday 16th September 2009
quotequote all
[quote]Jag back ends were very popular with the street rodding/drag racing boys, so more info may be available on their sites.
[/quote]

Not nearly as popular as the bulletproof Ford 9 inch.

grahamw48

9,944 posts

268 months

Wednesday 16th September 2009
quotequote all
Agreed....but this is England...land of rusty old Jags. ! wink

Brap_Brap

753 posts

239 months

Wednesday 16th September 2009
quotequote all
grahamw48 said:
Agreed....but this is England...land of rusty old Jags. ! wink


Aye, but look how many UK auto makers used Ford parts. Surely it's made its way that side of the pond?

heightswitch

6,322 posts

280 months

Wednesday 16th September 2009
quotequote all
Brap_Brap said:
grahamw48 said:
Agreed....but this is England...land of rusty old Jags. ! wink


Aye, but look how many UK auto makers used Ford parts. Surely it's made its way that side of the pond?
No.
The 9" ford is very much an american part.

All UK / german ford axles were English or Salsbury.

Not sure what the old ford big commercials ran.

Also an old live axle is a bit old hat these days. The 4HU is independant don't forget.

(and very heavy)

N.

grahamw48

9,944 posts

268 months

Wednesday 16th September 2009
quotequote all
Brap_Brap said:
grahamw48 said:
Agreed....but this is England...land of rusty old Jags. ! wink


Aye, but look how many UK auto makers used Ford parts. Surely it's made its way that side of the pond?
Yes, it's been available here for many years (ex-Mustang ?), and used on the above-mentioned hotrods,etc, but of course the Jag IRS was much more abundant and available in different widths, better suited to our narrow little cars from the fifties and sixties...not to mention a far more sophisticated basic suspension set up.
Dresses up very nicely too.smile

Pic courtesy of 'Rod and Custom'.



Edited by grahamw48 on Wednesday 16th September 21:41

Brap_Brap

753 posts

239 months

Wednesday 16th September 2009
quotequote all
I'll say this in defence of my JAg rear.. it looks VERY tough with the four built in (cast) gusset's. It got to be good for 450hp easily. Even the TVR drive shaft/half shaft UJ's are tough. My friend Jay, who's lent me his garage for this this agrees. My wedge has bigger UJ's and diff than his 1-ton dodge p/u truck. smile I actually measured the.... 1-ton pickup... 2.5 inch UK's.... TVR wedge half shafts, 3 inch IIRC. smile Built to take a beating.

Edited by Brap_Brap on Thursday 17th September 00:56