Art and others,
I am home now, and I have dug out my reference materials. I hope I'm not
repeating something someone else has said, but I didn't get to read all the
mail on this subject. I can confirm my previous statements, plus add a few
clarifications. The most convenient reference source are the photos in Graham
Robson's book "The Triumph TRs - A Collector's Guide," ISBN 0-900549-63-7.
These photos are on pages 41 and 42. These seem to be official factory
photos, and appear in many other publications as well.
Starting at the rear, and working forward:
1) Rear leaf spring hangers - Identical for both versions. The holes for the
shackles are just left empty on the IRS version.
2) Rear diff mount/crossmember - Almost identical. The live axle version
doesn't have the diff mounting pins or the support braces for same.
Otherwise, identical.
3) Shock mounts - Identical. Both versions use the same shock configuration.
There may be differences in the shock valving, but I doubt it. The shape of
the shock links are slightly different.
4) Bridge piece - Installed only on the IRS version. These pieces are the
same on the TR4A thru TR6 with one exception - the TR6 has two small pieces
added to support the body. The body is not supported here on the TR4A, 5, or
250, which makes sense, as the live axle version doesn't have this piece, yet
needs a body mount in this area. A stamped piece of steel mounted to the
center of the frame appears to be the point of mounting for the body on the
pre TR6 models.
5) Trailing arm brackets - The holes for these are present on all versions of
the frame, including the interior "anti-crush" tubes (my term for them - I
don't know the official name). The brackets are bolted to the frame, no welds.
6) Front leaf spring bracket - The holes for these are present in all
versions as well, including the inner "anti-crush" tubes. The brackets just
bolt on, no welds.
Converting a live axle TR4A to IRS would be relatively simple. The bridge
piece from any TR4A thru TR6 frame could be used. It is welded to the frame
in four places (or 8, depending on how you view it -- the welds start on the
frame side and continue over the top), all on the outside of the frame where
they are easily accessible. A few minutes with a grinder would have them off
the old frame, and four (8) quick welds would have them in place on the new.
I don't know if the TR6 body mounting pads would need to be removed, but I
doubt it. If they did, it would just take another few minutes with a grinder
to eliminate them.
The rear diff mounting pins can be bought, but they could also be very easily
made, as they are nothing but a steel rod with the end turned down for an
inch or so and threaded. The pin support braces could also be made if not
commercially available, as they are nothing but strips of metal with a hole
for the pins. It might be a little bit difficult to exactly match the shape
of the originals, but it isn't necessary to do so. Simple bends will do. I
believe the material is 12 gauge.
New tabs will need to be welded onto the frame for the brake lines. The live
axle has one flexible line, whereas the IRS has two, and the hard line
routing may be a little different. The emergency brake cables may be a little
different, but these are readily available.
>From that point on, everything is a simple bolt on operation.
Converting a TR4A, 5, or 250 IRS to a live axle is just as easy, if not
easier. Even converting a TR6 to a live axle is fairly easy, thank goodness!
Some mods will need to be made to accommodate the up and down movement of the
driveshaft, and maybe the bridge will need cutting or modifying to
accommodate the axle pumpkin. At this moment, I have a TR4A live axle
suspension setup on my TR6/V8 project, but the axle (a Ford 9") has not yet
been put in place, so I don't know just what bridge mods will be needed. I am
not going to completely remove it, as I plan to use the old spring mounts as
mounting points for tube shocks, and I don't want to try to rig up some other
means for mounting the body here.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://members.aol.com/danmas/
'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
'68 MGBGT---organ donor for the '74
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