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TR6 TR4A on a TR6 Frame?

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M

mclaugh

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My TR4A frame has a badly rusted rear half that is beyond repair (for me anyways). I have been told that I can use a TR6 frame, and just have to move the motor mounts. Whenever I hear the word "just" in a situation like this, I suspect my informant of passing along hearsay, and picture many unanticipated complications. So has anyone here actually grafted a TR4A onto a TR6 frame? What alterations are necessary?

Thanks,
-Tom
 
Time for this if you ask me

TR46.jpg
 
Good question. It's a solid axle 4A. The frame I'm looking at has the rear suspension, axles, etc. on it. So I believe I could leave that alone and essentially convert the 4A to IRS. Is that correct?

If I remove it all and install the solid axle parts, I would have to add the rear mount for the leaf spring. Anything else? Would the front differential bridge have to come out? Is the other bridge where the lever shocks mount the same?

Thanks,
-Tom
 
The front bridge would have to come out to fit the solid axle. The rear bridge is the same sans diff bolts.
 
Found it on the web. I think when I originally posted it many years ago someone knew the owners name.
 
LBCs_since_1988 said:
IMHO, just the opposite would look great. A clean TR6 front with a classic TR4 rear.
Click to expand...
As an ex owner of the TR4 (twice) and TR5 (once - sigh) I am biased, but I personally appreciate a clean Michelotti TR4 shape (without the side lights - even on the TR5) to the Karmann design.
 
TRDejaVu said:
As an ex owner of the TR4 (twice) and TR5 (once - sigh) I am biased, but I personally appreciate a clean Michelotti TR4 shape (without the side lights - even on the TR5) to the Karmann design.
Click to expand...

I agree, I almost left them off when I redid the body on my 4A (and one of the front wings was a replacement from a TR4, so I already had one missing).
 
Darrell_Walker said:
I agree, I almost left them off when I redid the body on my 4A (and one of the front wings was a replacement from a TR4, so I already had one missing).
Click to expand...

The PO of my 4A did leave them off. While I do like the look, I really wish he had left them on. Do you want to trade my TR4 fenders for your 4A fenders?
 
Hey didn't they put the stingray tail on the old style vette in 62 or so?

Check out the Ratco website I believe it goes into some detail about the differences in the two frames.
 
Not sure how complete the TR6 chassis is, but in addition to IRS, the stronger front suspension and anti roll bar would be a nice upgrade on the 4A.

I'm with Aaron on the mix and match car, the cleaner TR6
front end with the TR4 tail would be a good looking car.

Cheers,
 
Yes, it can be done. I did it on mine a few years ago.
I shot some video and will try to get it together in the next month or so when I have time. For now, here are the issues you need to know about...

Rear of car:
The TR4a IRS has rubber bumpers mounted in the wheel arch that hits a flat spot on the rear trailing arms if you go over a big bump. On the TR6, the rubber is smaller and is on a pedestal extension on the trailing arm and the point on the body where it hits is flat. For this reason, I used TR4A trailing arms on the TR6 frame so I didn't need to mess around with that issue.

Transmission Mounts:
I used a '74 TR6 frame from a car that was set up for a "J" type overdrive. That was an issue since the mounts were further back, and lower than the top surface of the frame. I had to make an adapter that connected to the existing location, and made the points forward and up for the non-OD transmission mounts. I didn't change the actual frame, so I can mount a "J" type anytime I want.


Engine Mounts:
Leave the TR6 mounts where they are. There are left over TR4A holes for the new mount to fit in the TR6 frame, but because the TR6 frame has some extra metal panels inserted in the shock towers to strengthen them, you don't have access to install the nut and lock washer on the TR4a engine mount inside the shock tower. Drill an access hole in the extra metal in the area where the added inner tower shell is installed. I didn't measure my hole location right, so I changed my access holes into slots so I could get the nuts / lock washers with sockets, extension and flex couplers in there. Not a big deal, but not something you would think about.

Steering Rack:
The TR6 engine is longer, so the steering rack location is further forward than normal for the TR4a. This raises issues with Steering Column length, use of the stock fan extension, stock cooling fan, and radiator placement.

Steering Column:
Since the rack on the TR6 is further forward, you must use the TR6 version of the lower steering column rod and U-Joint.

Cooling:
The stock TR4a radiator fits, but it must be slanted about 20 degrees toward the rear of the car to clear the hood. You will need to make your own new radiator top mounting brackets, or do what I did. I took my stock brackets, and flattened them on a press. That lengthened them and made them just right. Since the stock fan and fan extension will not fit, they were replaced with just a bolt in the front of the engine. Then I install an electric cooling fan, configured it as a pusher, through the radiator front. The down side is you have to do some custom wiring, and make your own bottom radiator hose. I went to my local auto parts store, and looked for something with the correct diameter, and about the correct angle, and cut exact size from what I found that was too long.

Body Modification:
There is one modification you need to do to each inner fender. There are 2 issues that are solved with the same modification: The first one is an interference issue with the boot for the relocated steering rack. The other issue is related to being able to remove the TR6 shock tower cross tube in front of the engine. If you do not make this modification, you will never be able to remove the cross tube (or the engine) without removing the body. I can't seam to figure out how to post an image, so if you need to see what the pieces look like that you need to cut out; I saved them and took a photo of them. Send me an E-mail

Brakes:
Use the tubes from the TR4a, since the TR6 has a dual brake system. I also added a power brake booster for a single pipe system. I used the TR6 front calipers but either will work.

Other:
I used the TR6 front skid plate, and a TR6 front sway bar.
That's about it. I may be forgetting something, but if so it is minor (like some different brake pipe clips or something) and it really doesn't matter. It can be done, and it’s a hassle if you don’t know what is involved. I only wish I could have found real answers several years ago when I was faced with a similar issue.

Good luck, and TR on.

Bryan
 
Great post Bryan. A fine example of what this forum is all about. :thumbsup:
 
Thanks Bryan! Exactly the kind of information I wanted, that only someone who has been there and done that would know.

-Tom
 
No problem. I think I figured out how to post a photo, so here are the two sections that need to be cut out. Look at the bottom of your inner fenders and it will be clear where to cut.

Bryan
 

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Thanks!
Thought you guys would get a kick out of this:
TR4A, on a TR6 frame, with TR4A running gear, and other TR6 stuff. And since I did the work, what else would I call it but...
 

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