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Jerky driveline fixed!!

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So I just had 3.55 gears installed on my GT to replace the 3.73. The installer is a retired NASCAR crew chief and was once crew chief of the year. He let his mechanic do the heavy lifting then he did the fine tuning and shimming. $611 install plus my parts from Ford Racing. (and he had to drop my Fays2 out of the way and reset it)

I picked the car up today and voila; zero driveline slop. What the heck? I called him up and said where did the driveline slop go? All you did was put in new gears and I assumed the slop was just part of owning the Mustang. He said the gears were built sloppy from the manufacturer and not unusual with this Ford rear.
Then he told me he left things just a little loose for my track use so the rear end would get less hot. Loose? I am loving his loose. The jerking is gone and shifting is far quicker and smoother (old MGW still). Feels like a darn BMW driveline or better. Just snick, snick through the gears. I tried to get the car to do some clunking but none to be found.
 

302 Hi Pro

Boss 302 - Racing Legend to Modern Muscle Car
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This guy could make a fortune setting up Mustang differentials. I'll have to look for a good diff guy in my area, but I'm keeping my 3.73's.

Thanks for the info.

Dave
 
I have to take mine to a speed shop as well... dealer did a horrible job when replacing my rear end from an accident. I have alot of backlash/slop and horrible gear whine since day one.
 
F.D. Sako said:
I have to take mine to a speed shop as well... dealer did a horrible job when replacing my rear end from an accident. I have alot of backlash/slop and horrible gear whine since day one.

Mine whined as well from day one. The car only has 4,500 miles on it and the dealer said "the whine is normal". When new if I got on and off the gas it would clunk and clang. My guy said it is a bit of an art to getting these just right. He would not give me an estimate as he said sometimes it takes three or four attempts to get the shims just right. So the best estimate was 400 to 800 dollars to get it perfected.

I went to 3.55 in my GT as I want to be able to use 35 tires and not run out of fifth gear on faster straights. I only have a 6,800 rpm limiter.
 
todcp said:
Mine whined as well from day one. The car only has 4,500 miles on it and the dealer said "the whine is normal". When new if I got on and off the gas it would clunk and clang. My guy said it is a bit of an art to getting these just right. He would not give me an estimate as he said sometimes it takes three or four attempts to get the shims just right. So the best estimate was 400 to 800 dollars to get it perfected.

I went to 3.55 in my GT as I want to be able to use 35 tires and not run out of fifth gear on faster straights. I only have a 6,800 rpm limiter.

I hear you on the ratios.. with smaller tires like 275/40/18 26" or sometimes measuring 25.5" - also the 275/35/18 only 25" if you are lucky the MT82 will top out way to quickly and the torque multiplication is stupid tire melting can't accelerate sucks. I went down to a 3.15 and the improvement was amazing, now i'm doing to a 2.73.

OP I also had a bad whine and the dealer swapped it, whine got worse! had a nice shop handle it - no more noise and less slop in the system.
 
Clunk and slop from day 1 (normal, but not refined feeling)
Rear end whine at 55-75 MPH from around 1500 miles.

2 dealers evaluation were identical: will fix the whine and will likely come back after 5000 miles...lol

The potential malfunction is likely none, which matters the most.


OP, I am glad and impressed that so far you feel no clunk or slop!
 
I also went from 3.73 to 3.55 and added a Boss Torsen and 1pc DS last year. I would say mine is on the very "loose" side but works well despite the slop. I think the Carbon Fiber DS I got probably helps mask some of the slop. Ultimately I ended having to change my shifting and clutch engage/release style a bit in order to minimize hearing the clunking.

Anyway, I'm sure you will like the 3.55's. I know I do. I feel they made a nice difference for the better in terms of shift points despite numerically not being much of a change from the 3.73's.

I guess if mine ever lets go from having too much slop I will be sure to request the setup be a bit tighter next time :)
 

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