TR7 back axle on to a Dolomite

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2F45T4U · #1 Post by **2F45T4U** » Sat Dec 30, 2006 7:10 pm

Os the 5 speed TR7 axle the same as the one that is used on the V8 TR8. Will it handle the extra power of a V8?
Hasn't AdamF's V8 Sprint got a narrowed TR7 back axle on it? If it was left as its standard size (4 inches wider?) and took the power of a RV8 then that would solve two problems. What to put on to a V8 dolomite and what to fill bubble arches with

SprintV8 · #2 Post by **SprintV8** » Sat Dec 30, 2006 10:52 pm

Unless your planing on building a super duper 3.9+ V8 with shed load's of power I'll save your money and fit a Sprint axle and make sure it's polley bushed.

Sprint Race cars take more power than your gonna throw at it with that 3.5 V8.

2F45T4U · #3 Post by **2F45T4U** » Sat Dec 30, 2006 10:57 pm

I have a TR7 remember.... Thought the Sprint axle gave up at lk 280ft lbs of torque?

SprintV8 · #4 Post by **SprintV8** » Sat Dec 30, 2006 11:07 pm

I doubt if you have much more power than Lewis.

Stuff a Sprint axle in there and save a few quid.

If it should go west then upgrade to the TR8.

Cost may be important here.

Who's gonna narrow it for you.

DavePoth · #5 Post by **DavePoth** » Sat Dec 30, 2006 11:10 pm

RPi engineering's full race 5.2 RV8 only makes 360, with a standard 4.6 getting about 285. I think a sprint axle would be fine.

2F45T4U · #6 Post by **2F45T4U** » Sun Dec 31, 2006 1:29 am

being only 4 inches wider then bubble arches will solve it

i'm talkin foot pounds of torque. I'm sure I've read that ALG 1K was breaking Sprint axles at 280 foot pound of torque. Being as a standard SD1 engine is 155hp and 198 foot pound and the V8 Lewis has is 165hp with 225ft lb then with a carb and cam shaft change I can see the 280 ft lb figure being exceeded easily

Lewis · #7 Post by **Lewis** » Sun Dec 31, 2006 2:40 am

Nah, you won't worry the Sprint axle. My friends tuned 3.5 with nice extractors, fizz-bang ignition, Carter AFB, phenolic spacer, Kent high-torque cam, good strong known engine and makes 200.5BHP and 221lb/ft so you haven't got any issues.

Davepoth is indeed correct as well - the standard 4.6 EFi makes a stump-pulling 277lb/ft at 3000RPM

As an example, the 'generic' 5.0 litre Wildcat makes 335lb/ft at 5600RPM and that's a damn trick engine.

Plenty enough from any of them though

Hasbeen · #8 Post by **Hasbeen** » Sun Dec 31, 2006 12:53 pm

We have a TR8, with a 4.6 Rover V8, tuned moderately.
We went through 3 diff centers, & were about to loose the 4Th,
when we fitted a diff with a Holden [Vaxhaul] Monaro limited slip
center.
This is still there.
It was always the planet wheels which failed.
A limited slip TR7, or 8 diff would probably have worked, but worth
their weight in gold on Oz.

AdamF · #9 Post by **AdamF** » Fri Jan 05, 2007 4:07 pm

2F45T4U wrote:Hasn't AdamF's V8 Sprint got a narrowed TR7 back axle on it?

Yes it does. Well, a TR8 axle according to my documentation...

Don't know if it needs it though.

I have a receipt for the narrowing - I'll dig it out for you if you want to know who and how much. The receipt does date back to circa 1994 though!

The TR8 unit I've got fitted does give you more sensible final drive than Lewis's though to make better use of the torque.

Adam

Lewis · #10 Post by **Lewis** » Fri Jan 05, 2007 6:01 pm

I'd considered it briefly as we were offered an axle with the sale (not narrowed, mind and with the wrong diff) but mine turns 2800RPM at 70mph which is fine, really.. about 1100RPM at 30mph in 5th.

2F45T4U · #11 Post by **2F45T4U** » Fri Jan 05, 2007 6:33 pm

Woo hooo £50 will get my prop made to fit

gmsclassics · #12 Post by **gmsclassics** » Sun Jan 07, 2007 10:11 am

The Sprint rear axle may handle the power in a straight line, but, add wider, sticky tyres and put in on a racetrack and the problems start. The half shafts diameter is quite narrow and the shaft flexes under high cornering forces. This lets the oil out all over the brake drums and then the tyres. Makes for interesting handling!

You either need special thicker half shafts or machine the axle casing to take extra bearings to stop the flex. Neither are cheap options.

If you are serious about changing the axle, how about a Ford Escort / Cortina/ Capri. They are the same width within a mm or two, and will fit without body modifications. Some Capri ones even comes with 9" drums so is very comparable to the Sprint. Obviously mountings from a Sprint axle need to be welded on (in exactly the right place) and wheel studs re-drilled to fit Dolomite wheels.

Advantages are that these Ford axles are very strong and you have access to the full range of easily changed diff ratios that come with the Ford range. LSDs for Escorts are also easier to get than Sprint ones.

Food for thought?

Geoff

Neil907 · #13 Post by **Neil907** » Sun Jan 07, 2007 7:15 pm

Are you talking about a ford english axel or an atlas one.
cause I thought you could snap the english half shafts with about 150 bhp from a pinto.

gmsclassics · #14 Post by **gmsclassics** » Mon Jan 08, 2007 9:25 am

I'm not that familiar with Ford to know the differences. Half shafts are certainly more substantial (thicker - 27mm diameter) than the Sprint ones. I must be putting 190bhp through with no problems and I know of Escorts running BDA motors with these. It seems strange with the racing pedigree of Escorts that they would break at 150bhp, but I suppose anything is possible. Dumping the clutch at 6000rpm in first gear too many times on say a drag strip will certainly test the worth of any diff/half shaft assembly and show up any metal fatigue.

Neil907 · #15 Post by **Neil907** » Mon Jan 08, 2007 5:36 pm

The english axels have a front load diif and look like an 1850 axle.
The atlas axles are rear load.
I dont know too much about them myself but a mate is building a group 4 mk1 and has just changed the axle from english to atlas.

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