I decided to replace my low miles traction lock with a true trac diff and 3:73 gears about 600 miles ago. I had an experienced person change and set up the diff and with all new bearings. I had instructed him to set it up with the least amount of lash possible. When I reinstalled my diff every thing seemed good (except for my notchy 3650 trans) but there are two problems---one is im not happy with the 3:73s as this ratio seems to be either too high or too low depending on what gear and what speed so I wish I stayed with the stock 3:27 gears or bumped up to just the 3:55s---for me 4:11s would have been too low. My other problem which is not good is that in the last 200 miles the diff now has way too much lash and Im getting too much clunk in the drivetrain to the point where I dont want to drive the car. I talked to the guy that set it up and said he will make it right if I bring the diff. back in-----holy crap as most of you know that is a lot of work with the I.R.S. So anyways what could he have done wrong setting up my diff? Also Im thinking when he re-does my diff that I should go back to my stock gears and maybe even putting the traction lock back in??? who has experienced something like this with the diff and gear ratio and any other thoughts would be appreciated.
New true trac diff with 3:73 gears have a delimma
- Thread starter FIREBALL
- Start date
What was the backlash that was setup? Are you sure when you put it all back together all the bolts are tq to spec? Have you re checked tq since driving? Are any of the bolts used a 1 time use bolt? Just want to make sure you have pin pointed it the issue. Also the 3.73 are a great gear to have. But 410s would have been better. The 3.27s were enough gear for those cobras. They need RPM.
My guess would be the crush sleeve failed and it threw off the lash. You're the first person I've heard of that didn't like the steeper gears. I had 3.90's and the only time I didn't like them was on the freeway. They put me right in the zone for a loud BOV.
This is an originall 11k miles car and the driveshaft and joints are still tight and like new. For mostly street the 3:73s put me in some in-between rpm range from 2nd to 4th gear that I dont like and I know that for me the 4:11s would have been way too low. I thought about the crush sleeve and that was my first guess so I asked my gear guy about that but he couldnt remember if he used the crush sleeve or shims. I dont have the diff back out yet so I dont know about any loose bolts but when I jacked up the car and put the trans in gear and then held the drive shaft and rotated the rear wheels there is major slop in the differential that wasnt there before.
Theres for sure a crush sleeve and sure there is a shim on the pinion. Sounds like its gonna have to come apart something sounds like it failed. Sorry to hear. Depending on what failed there maybe damage to the gears so you may end up replacing them.
Read this thread:
https://www.svtperformance.com/threads/8-8-truetrac-problems.715621/
It seems like a lot of people are not happy with their TrueTrac differentials. It may not be ring and pinion gear lash you are experiencing. What oil are you using? Eaton specifies mineral oil (over synthetic) with no friction modifier added. Many, if not most, synthetic and some mineral oil gear lubes, have friction modifier already added from the manufacturer.
https://www.svtperformance.com/threads/8-8-truetrac-problems.715621/
It seems like a lot of people are not happy with their TrueTrac differentials. It may not be ring and pinion gear lash you are experiencing. What oil are you using? Eaton specifies mineral oil (over synthetic) with no friction modifier added. Many, if not most, synthetic and some mineral oil gear lubes, have friction modifier already added from the manufacturer.
This is so true.
And you have to watch it, because so many shops think that they know better or just don't know what you have in the diffy at all.
The oil used should be Valvoline no synth or Castoil no synth.
Unfortunately that slop in the Detroit TT is what makes it work so well. It is the nature of the beast. You learn how to drive with it. I like stuff that doesn't break.
I have 3.73 as well.
I nearly got that true trac diff, but luckily my shop warned me about it. Got the auburn pro series diff instead. Locks up hard and fast, much more than even the ford racing unit did. Also, no clunk.
I wouldn't put that true trac back in if you are annoyed by clunking.
I wouldn't put that true trac back in if you are annoyed by clunking.
The first 300 miles there was the normal light lash/clunk sound but now it has gotten really bad- beyond what I think is normal even for the true trac. With the driveshaft held still I can rock the the wheels back and forth about 3 1/2". I used Castrol 75/140 non syn. and no modifiers.
From what I have read some have set their diffs up with no crush sleeve---they used a solid spacer and shims. well when I get the diff out and it turns out to be the normal tru track internals that are causing it then I will probably scrap it and go with a Torsen, an expensive mistake on my part. I Had Torsens in my last two cars and loved them, dont know why I even went with the Tru Track in the first place!
From what I have read some have set their diffs up with no crush sleeve---they used a solid spacer and shims. well when I get the diff out and it turns out to be the normal tru track internals that are causing it then I will probably scrap it and go with a Torsen, an expensive mistake on my part. I Had Torsens in my last two cars and loved them, dont know why I even went with the Tru Track in the first place!
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Keep us posted.
I agree.
Don't feel you have to stay with the Detroit TT.
You can get something for it.
I might have gone with something else had I had the cash.
The TT is the poor man's diffy and it holds up to a lot of power.
keep us posted.
Ok it turns out it was too much lash mixed with the 3650 trans slop. After doing more research I mostly see the tru tac is one of the best for all around high performance and racing---not so much for the street, so Im going to go with the milder Torsen T2 that is better for the street and only occasional track or auto cross. So If anybody is interested in my 600 mile tru trac with new 3:73 gears or my original 10k traction lock (2001 cobra)diff that had 0 issues---PM me, I will give a very good deal.
I like having my diffs built without a crush sleeve because it makes it easier if you ever have to remove the flange for any reason (to swap out pinion seals, for example).
Also, I love my trutrac - it has been very good to me for many years and many hard-driven street miles and dragstrip outings.
interesting.. I was going with the ratech solid, but never installed it.
I got leaking at the pinion after a year+ with the TT.
The entire diffy was redone along with the TT install.
I just had a shop put in a new seal, as I was headed to FL soon.
I still have the ratech spacer,,
My car is set up like a road racer..I like her like that.
Q: Do you think that the TT had something to do with the pinion leaking so soon after an install? I'm wondering whether the TT "slop' tends to hammer the crush sleeve a bit?
Good to know.
shockwavef399
New Member
sorry to reply to an old post but i came across this post looking for something else. my 3650 was also notchy, but i found the problem pretty quick. i just bought my car in march and i changed every fluid in the car. the trans had over 5 quarts of fluid in it which is WAY to much. i drained it over night and filled it with exactly 3 1/2 quarts of pennsoil synchromesh. you dont fill that trans until fluid runs out of the hole. now, my trans shifts like butter and i've driven it about 1k like that and its perfect. as for the rear end, i had a shop that specializes in ford's completely overhaul the differential in the rear end with all ford racing parts, 3.73 gear, the high torque bearing and seal kit, the trac loc rebuild kit and the hardened differential cover all from american muscle. yea i dropped some cash but it was totally worth it. i've had 0 problems and it hauls ass, that ratio and combination seems to work perfect for me. hopefully you've found your issue, best of luck
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