View Full Version : Moss differential and frt susp strengthening kit

07-20-2011, 09:44 PM
I am ready to get my frame on my TR4A IRS sandblasted and can start to put my car back together after that. Moss sells strengtheing kits for both the differential supports and the front suspension lower A frame. I am aware of the weakness in the single bolt which holds the A frame on and intend to order the uprated two bolt connector (TR6 style I believe). I was wondering how neccessary it was to install these kits if the supports seem to be in good condition? Is this something recommended for average driving? No racing or autocrossing etc. I am planning on using uprated front springs. Any input on this would greatly be appreciated. Bruce

07-20-2011, 10:02 PM
If you have it that far apart, I would definitely have the gussets installed.

07-20-2011, 10:43 PM
As said, if you're that far, spend the extra couple hundred bucks. It's some of the best, if not the best extra insurance you can have for your TR4A frame/structural wise.

07-21-2011, 11:29 PM
Ditto on the TR4A front suspension reinforcement. I pulled my front right wheel off while reversing in a turn with a "correct" lower A frame. All that you can do to reinforce it is worthwhile.

07-22-2011, 03:16 PM
I became aware of the potential for trouble years ago when I had another '67 TR4A IRS. A friend and I were let's say sport driving each other for six or seven miles until we got to where he lived. At the very moment I turned into his driveway at very low speed my left lower front suspension broke off. If it had happened just a minute before it would have been bad. What broke was not the mounting bracket on the frame which is what the Moss kit fixes but the single attaching bolt. In reading forums etc. I never see anyone refer to using these reinforcing kits for either the front suspension or the differential so I did not know if it was a "racing" thing or something the average driver should do. How many of you have installed these kits?

07-22-2011, 04:14 PM
I have the front gussets on my car. One of the brackets did separate from the frame, when the car was ~15 years old. And it wasn't due to rust. Though I do drive in a spirited manner.

I don't have the diff bracing, but would have installed it when I did my frame-off if I had known about it. I actually had the rear bracket on the diff break.

08-03-2011, 06:01 PM
It's just money, I ordered the front suspension kit and some reinforcing plates from The Roadster Factory which has the differential mount repair pieces listed separately. My car is not cracked or broken in either place so I only ordered the strenghing pieces to weld in. Also ordered the urethane mount pieces for the differential which I understand reduce the flex (therefore load) on the right side front mount which apparently takes the bulk of the load. As soon as they come in off to the sandblaster, weld pieces, then POR 15 the frame. Can start reassembly after that.

08-04-2011, 11:10 AM
Good decision - issues can/do show up even if you are not racing. If your pins are fine then boxing the mounts in should be OK. That said carefully inspect the pins for cracks.

Poly mounts will make the problem worse if you don't box the diff since they transmit more stress than the rubber ones.

08-21-2011, 06:38 PM
Ok just got frame from sandblasting and find the right front differential bracket is cracked from side to side in the middle where the pin comes through. Actually it is not just cracked but broke separating the front and back halves. Can I weld the crack which is easy to get to and install the side reinforcing plates I just got in from TRF or do I need to replace the pin and bracket as well? In addition my front A-frame attaching point is slightly cracked where the single bolt attaches (67 TR4A IRS) but I did get the reinforcing backing plate and side braces for the front.

08-21-2011, 08:13 PM
I just reinforced my TR4A Diff Mounts, both front and rear.

Before proceeding, I would highly recommend you speak with Richard at GoodParts in Pa.

The kits from the Big Three are good. With some help from Richard, I opted to have mine cut from steel stock by my friend who is also a professional welder. We did it "frame on," but it would have been easier off.

We reinforced both bridges running a piece against the bolts front to rear, then boxed each bolt in by welding along the edges of the old brackets. Somewhere here I have an old post with a photo.

Good luck. Do it.