7.5 trac lock question

Topic: 7.5 trac lock question (Read 1992 times) previous topic - next topic

7.5 trac lock question

October 07, 2017, 09:38:20 AM

My oldest sons 88 sport bird has an aod & 7.5 in 2:73 rear trac lock rear.

He is in discussion with an 87 stang owner that has a 5 speed & 7.5in 3:73 track lock rear.

the stang owner wants to go AOD with a fuel economy rear gear.

My son wants to make his bird a 5spd and move to 3:73

question
can both parties simply trade rear end internal rotating parts?,,,,

the total plan here is they trade transmissions & rear gear internals.

what we dont have for the bird is pedals..gotta research if stang pedals go into ours or not.

7.5 trac lock question

Reply #1 – October 07, 2017, 10:58:05 AM

Last I was aware, an 87 Mustang with a 5.0 would have an 8.8 rear end. Maybe some research to verify. removing and installing a pinion gear is sort of an ordeal, and setup is extremely sensitive to proper pinion depth and ring gear backspacing. I'm an ASE Master, and even I don't want to do it. It's a pain in the ass, and I can count on one hand how many I've ever set up. I don't own the measuring tools, anytime I did one the tools for it belonged to the shop.
I'm not sure I'd put the time and money into a 7.5 that you're probably still going to break eventually (assuming mods and power adders). Go 8.8

7.5 trac lock question

Reply #2 – October 07, 2017, 11:04:19 AM

Stang pedals work fine....I have 88 mustang pedals in 87 TC.

I may be mistaken but the rear in the Stang should be an 8.8 unless it's a 4cyl which would not be a trac-lock unit. If it is truly a 7.5 track-loc yes you could swap internals but it likely be easier to swap the whole rear over. Personally.....I would look for an 8.8 rear.

John

7.5 trac lock question

Reply #3 – October 07, 2017, 11:21:33 AM

My understanding is the Stang pedals fit fine. I would also agree, I think it would be easier to swap the whole rear ends.

7.5 trac lock question

Reply #4 – October 07, 2017, 12:47:13 PM

Quote from: TheFoeYouKnow;463122

I'm not sure I'd put the time and money into a 7.5 that you're probably still going to break eventually (assuming mods and power adders). Go 8.8

+1. I broke the out of the 3.73 geared 7.5" rear in my car. Spun the pinion bearing causing the pinion gear to move back and forth, banging off the carrier. Caused a hell of a noise/vibration. Went with a 3.73 geared 88 XR7 8.8" as a replacement. See below for noise :hick:

https://www.youtube.com/watch?v=4xzkctodX0E

7.5 trac lock question

Reply #5 – October 07, 2017, 01:17:54 PM

Only 7.5 rear with 3.73 gears I know of is behind a 2.3 n/a stang. Aid wouldn't swap.

To swap the rear, I'd swap the whole rear end then swap the brakes /axles over. Otherwise you would have to get new crush slaves and reset both rear ends.

7.5 trac lock question

Reply #6 – October 07, 2017, 01:51:28 PM

Quote from: Haystack;463131

Only 7.5 rear with 3.73 gears I know of is behind a 2.3 n/a stang. Aid wouldn't swap.

To swap the rear, I'd swap the whole rear end then swap the brakes /axles over. Otherwise you would have to get new crush slaves and reset both rear ends.

Agreed, all 5.0 Stangs from '86 used the 8.8" rear... From factory lowest ratio 8.8" was 3.27 and those were automatic only...

I junked a '89 Stang half motor that had the 7.5" 3.73...

7.5 trac lock question

Reply #7 – October 07, 2017, 02:41:54 PM

Find you a V8 '94-'98 Stang, do a full 5 lug, complete rear swap, AND gain discs. More work upfront, but......

Your other 8.8 option with deeper gears is a TC rear. Still disc, gonna be the same work to convert to rear discs for the car, to me the downside is 4 lug. So much more of a selection of wheels with 5 lug rather than 4. The one plus is that if the TC rear is from a stick car, it's 3.55 and if it's from an auto TC, you'll have a 3.73.

Myself, I'd find a wrecked '95-95 V8 Stang, pirate all the suspension shiznit, rebuild as needed and pop in. The pedals from any stick Stang (Fox, SN95 up to '99) will work, though there's a couple minor differences with regards to 2.3 vs 5.0 pedals. Both will work however.

Whatever you do, pay attention to clutch cables..there's threads here that spell out which ones are junk, and which ones are better. I think Lou had some issues a time or two, IIRC.

7.5 trac lock question

Reply #8 – October 07, 2017, 08:52:15 PM

We are already 5 lug swapped on Mason's 88bird and rear disc with upgraded front disc

not sure what motor is in the stang we are talking about but,, the cover tag says 3 73 and both rear wheels off the ground turn one the other turns the same direction... and its a 7.5.

I am going to likely talk him out of it though,, he has some dcent motor mods and likley just enough to break the rear when he plays around.

i can imagine he might enjoy 3 73 a little too much and break it... i can also respect the advice,, i knew 8.8 would be better but they are not easy to find around here.

he lives in charlottsville va so its not like i can help unless he comes over here to home which is where the work would be done.

thanks!

7.5 trac lock question

Reply #9 – October 07, 2017, 10:20:02 PM

If he's not drag racing at a 1/4 mile track the 7.5 should last street driving. I broke mine after a couple violent track launches.

7.5 trac lock question

Reply #10 – October 07, 2017, 11:58:38 PM

Quote from: jcassity;463138

We are already 5 lug swapped on Mason's 88bird and rear disc with upgraded front disc

not sure what motor is in the stang we are talking about but,, the cover tag says 3 73 and both rear wheels off the ground turn one the other turns the same direction... and its a 7.5.

I am going to likely talk him out of it though,, he has some dcent motor mods and likley just enough to break the rear when he plays around.

i can imagine he might enjoy 3 73 a little too much and break it... i can also respect the advice,, i knew 8.8 would be better but they are not easy to find around here.

he lives in charlottsville va so its not like i can help unless he comes over here to home which is where the work would be done.

thanks!

For '87 only factory engines were the NA 2.3L half motor & 5.0...

If it's a 4 banger the T-5 transmission is also weak and would require all the associated 5.0 clutch components, bell housing, flywheel etc... Plus the AOD won't fit a 2.3...

7.5 trac lock question

Reply #11 – October 08, 2017, 01:43:02 AM

A bunch of the 3.73 and 4.10 gears were traction lock. I bought two 3.73 rears from 4 banger mustang and one from a 1984 turbo diesel mark7 and they were all locking diffs. Never did use them.

The weak point of the 7.5 is in the traction lock assembly, which you also can't really get rebuild kits for either. In my opinion an open diff is fine unless you wanna hit the track and I've seen cars go low 12's and high 11's on them no problem. But they seem to be like t-5's. Some blow apart treated like glass, others take a beating.

Out of all my cars (15 now) and probably over 500k miles that I've personally put on already high mile cars, all had the 7.5 and ive never broke any of them. Even when I had my 87 with a sn-95 t-5. I put six sets of motor mounts in it in about a year of driving. With a open 2.73, 275/60r15's (28" tall almost 11"wide) and a 3.35 1st gear, I would slam the car in gear and dump the clutch at wot at 25mph. The car would either dead hook or smoke a tire until I shifted.

The 7.5 rear is way stronger then people give em credit for. Its almost always the locking diffs that come apart and eat everything else.