Identifying rear axles

[Huckleberry]

Hello folks,

I am finally getting back to work on my TR8. I have a TR7 5-spd. rear axle which I wish to use in place of the existing 3.08 rear which is noisy and a bit long-legged for my taste. I was assured that the replacement axle I bought was a 3.67 (that's the typical ratio for a TR7, right?), but I'd like to be certain. The axle seems to be in good shape internally, but it is a rusty lump on the outside. Can anyone tell me where to find the part number and what the different part #'s are for the various ratios?

Thanks very much for any help,

Huckleberry

Assembly is the reverse of disassembly

[Odd]

3.63:1 was a fourspeed axle ratio, together with the 3.27:1...

The 5-sp axles had either 2.84:1, 3.08:1, 3.45:1 or 3.90:1
with the respective number prefixes RH, CM, CL and CH stamped into the underside of the main differential housing.
But the ONLY sure way to know what it is you've got is to 'turn and count' since axles can easily have been rebuilt/
altered over the gone 30+ year period...

[Jolyon39]

Hi,

The four speed axle is a light weight thing with a "round" back plate. This was off the Morris Marina and is not suited to the power of a V8. I do not think teh prop shaft from teh 5 speed will even bolt up to it.

You want an axle off a 1977 or 78 car onwards.

Jolyon

[RJS]

I have a 3.45 in my 8, and I think it is just right. When I first got my car, a previous owner had put in a 3.90 (I assume the original broke).

You will also have to change the speedo drive gear so your speedo is correct. I forgot what color / tooth count I changed to get it right. Once you get to that point post a question about it and I will dig out my records.

Rob

[Hasbeen]

Huck, the standard ratio, in a 5 speed 7 is a 3.90.

We fitted one of these, off my spares 7, to the 8, when it broke its
3.08 diff one christmas, & no one was open to supply replacements.

It is a bit silly driving around, with a V8 roaring it's head off at
3000RPM, just to do 100Km/H.

Even with the relative hot 4.6 in it, the 8 has more than enough low
down torque, to accelerate quite briskly from 2000RPM, in top, at
100Km/H, & the fuel consumption is much nicer.

Unless you had the thing so highly tuned so it had nothing under
4000RPM, I feel the 3.08 is quite low enough in our light cars.
It's quite fun to drop back a couple of gears, at 100Km/H, & floor
it, when someone in a modern gets rude. However I can see how it
would also be fun to cruise away from them in top, while appearing
not to notice them.

Hasbeen

[Underdog]

Since you are here in the states I can assure you it's either a 3.90 or 3.45. The 3.45 was only put in the later cars, usually 1981s in conjunction with a taller 5th overdrive in the trans. If you take the rear cover off, you can simply count the teeth on the ring & pinion. Divide the pinion into the ring # and you will have your ratio. Actually, I think the #s may be stamped into the ring gear but I don't quite remember.

I have a 3.45 with a Quaife in my car. Quite a difference in accelleration. I know the 3.90 would cut my time at the dragstrip but it would totally ruin it for street cruiseing. For me, the 3.45 is a good compromise.

I just read Odd's post. Better make sure you didn't get a 4spd axle. They're only good for boat anchors.[xx(]

Jim Underwood
72 MGB BRG
80 TR8 Persian Aqua
If women don't find you handsome, they should at least find you handy.

[FI Spyder]

Rather than go down to a 3.45 rear end better to put UK 9.25 pistons in the V-8. And then maybe headers and hotter cam if your state allows. Unless all you do is go stop light to stop light. I don't know about you but I don't like reving high at highway cruising speeds. That's why I'd like a 3.45 for my TR7. I feel like I need a sixth gear. The only time I need my 3.90 is going up my steep driveway from a standing start.

If you don't want to soup up your V-8 you should look into a Buick V-6 conversion. Lots of power with low reving highway cruise.



TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra