TBird rear lower arms longer than Mustang?

Topic: TBird rear lower arms longer than Mustang? (Read 2002 times) previous topic - next topic

TBird rear lower arms longer than Mustang?

May 29, 2008, 10:03:01 PM

I got a surprise today when I was ready to install BBK rear lower control arms on my 88 turbo coupe project car. The BBK (Fox Mustang) arms are 1/2" shorter center to center than the TBird arms. This was a surprise because I thought all the Foxers had the same arm dimensions. I'm not sure what way to go. Install them and buy adjustable upper arms to get pinion angle right (wheel may not be centered). Or redrill new holes in the axle housing brackets to get the axle back in position. Have any you guys come across this concern? Thanks....Ken.

TBird rear lower arms longer than Mustang?

Reply #1 – May 29, 2008, 10:15:41 PM

That's weird. I'm running Hotchkis LCAs on mine and I had no issues installing them. Of course my car is an '83, so maybe the rear LCAs are different. I did have to retain my Thunderbird uppers because the Mustang units are shorter. I boxed my uppers to make them stronger.

Wish I had some good advice for you.

TBird rear lower arms longer than Mustang?

Reply #2 – May 29, 2008, 10:23:06 PM

Quote from: BadShoe;221208

I got a surprise today ....

Yes, not all Foxes are created equally. (T-bird's rule.

) Bird LCAs are longer than the Pony's by three quarters of an inch.

TBird rear lower arms longer than Mustang?

Reply #3 – May 29, 2008, 10:33:45 PM

ivygreen, if you used the TBird uppers because the Mustang units were shorter. I would thing the lowers were the same way. Did you check the old ones against with the new lower arms? I'm sure if I didn't check the ones I got, I would have installed them without seeing a concern. Likely get a little driveline vib from a high pinion but not sure just yet.

TBird rear lower arms longer than Mustang?

Reply #4 – May 29, 2008, 11:14:18 PM

You COULD just order the CHE ones.....

http://www.cheperformance.com/cartgenie/prodList.asp?scat=30

On a side note, our rear upper control arms are interchangeable with early Chevelle ones (68-72)

TBird rear lower arms longer than Mustang?

Reply #5 – May 29, 2008, 11:23:27 PM

I got the CHE (adjustable) lowers and uppers, MM also makes lowers for our cars.

TBird rear lower arms longer than Mustang?

Reply #6 – May 29, 2008, 11:46:41 PM

Quote from: BadShoe;221215

ivygreen, if you used the TBird uppers because the Mustang units were shorter. I would thing the lowers were the same way. Did you check the old ones against with the new lower arms? I'm sure if I didn't check the ones I got, I would have installed them without seeing a concern. Likely get a little driveline vib from a high pinion but not sure just yet.

You know, you may be right. I don't remember checking them against one another, but they've been in there for years and I don't have any problems...no vibration, nothing. Also, the rear tires are still centered in the wheelwells. Hmmmm. Now you have me concerned...

TBird rear lower arms longer than Mustang?

Reply #7 – May 29, 2008, 11:54:55 PM

I used the Mustang-length South Side Machine Lift bars in my old '86 for several years. Never had any issues. It did ride like a truck though...those SSM bars are hell on the street LOL.

I've never believed any of the talk about Mustang LCA's ruining anything on our cars. The roughly 1/2" difference in length (center to center) of the arms is mostly offset by the 4" longer wheelbase between the Mustang and the Cougar/T-Bird. Pinion angle will still be well within the 0-to-4 degree optimal setting. Any rear end rotation (viewed from the side) will be negligible.

In short: there's nothing detrimental in using Mustang rear LCA's on our cars.

TBird rear lower arms longer than Mustang?

Reply #8 – May 30, 2008, 12:27:49 PM

Thanks for all the input. The CHE units look like the way to go but I already have the BBK's. I'm going the reinstall the stock ones without the springs, take some measurements and angles. Then loosely install the BBK's, take the same measurements. Compare and see what I've got. Check back another day...Ken.

TBird rear lower arms longer than Mustang?

Reply #9 – June 06, 2008, 01:24:13 PM

An update on what I found. After checking pinion angles with the old lower arms then checking with the BBK arms, it shows a bit too much change for me on this car. At what would be the middle position or curb height, the pinion was about 5 degrees up from stock which is the opposite direction that I want for a street/strip car. Also tried using Mustang upper arms (which are 1" shorter than the TBird arms) and that caused the pinion to dive down below the stock Bird spec. (likely because the Mustang upper floor mounting points are closer together than the TBird's). So I tried a trick by drilling a new hole on the stock Bird upper arms 5/8" forward from the rear hole (installed bolts in that hole with the BBK lowers). This tested out having the same pinion angle as the old stock setup throughout the axle swing up and down. The axle is about 1/2" or so closer to the front but this should be fine as long as the driveshaft has enough room. However, after doing all this checking and measuring, I believe I'm going to buy the CHE TBird lower arms because this is likely the best setup in the long run....Ken.

TBird rear lower arms longer than Mustang?

Reply #10 – June 13, 2008, 06:51:58 PM

Quote from: EricCoolCats;221235

I've never believed any of the talk about Mustang LCA's ruining anything on our cars. The roughly 1/2" difference in length (center to center) of the arms is mostly offset by the 4" longer wheelbase between the Mustang and the Cougar/T-Bird. Pinion angle will still be well within the 0-to-4 degree optimal setting. Any rear end rotation (viewed from the side) will be negligible.

In short: there's nothing detrimental in using Mustang rear LCA's on our cars.

True dat. I've had 1991 stang LCAs on my '88 Cougar for 50,000+ miles.

I replaced them with Hotchkiss ones and hated the ride, so I had the stockers boxed and switched back. Now if only I could find replacement rubber (not poly) for them.

TBird rear lower arms longer than Mustang?

Reply #11 – June 19, 2008, 09:39:17 PM

Quote from: EricCoolCats;221235

In short: there's nothing detrimental in using Mustang rear LCA's on our cars.

True, except it makes the rear wheel location look weird.