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Motor lift vs tranny drop

879 views 9 replies 7 participants last post by  bruinjeeper 
#1 ·
I've got a 95 yj 2.5L automatic that I just put a rough country 2 1/2 leaf spring kit on with 31 10.5 15 wheels and tires. Did extended brake lines front and rear now I have the ever famous driveline vibration that I never had. I want to get some....... Suggestions if you will about 1" motor lift vs the 1" tranny drop. I know I have to do one or the other but not sure what one to do... Had some 5/8 spacers laying around so I threw them in for a small tranny drop to see if it helps and it got rid of most of it. Still has the vibe at 30-35 mph. This was only for testing only and will be removed. So what do you run/suggest? 🤔
 
#2 ·
i have your exact setup regarding driveline except with 3.5" springs. tcase drop didnt do it enough for me... needed both. but that is 1" more of lift...

i'd go 1" MML to start as its a pretty good option for future aspirations (if you had any) and you keep your belly clearance. just my .02.

Working on that SYE and driveshaft funding now though
 
#3 ·
Part of your problem is Rough Country puts those 6° shims on there. A transfer case drop won't fix it like you think it will. Been there, done that. What you need to do is remove those shims, reinstall the center pins, bolt the leaf springs back up, and then do the transfer case drop. You might want to put 2° shims on the springs to slightly angle the pinion up at the transfer case just slightly since the drop will angle the transfer case down just a bit. But I can promise your vibes won't really be fixed like you want just by doing the drop, since the shims are there and are so tall. It's way too much of a shim for a tcase drop.

On the other hand, they're perfect for a SYE and CV driveshaft so since I ended up eventually going that route, it worked out nicely for me in the end with those shims.
 
#4 ·
I have a 95 YJ 4.0L with I believe 3-3.5 suspension lift. (I'm not 100% sure which, I'm basing on measurement using ground clearance.) The place I purchased it from had no idea what was done to it. It does have a trans drop. I have never noticed any vibes. No SYE installed. I have a manual trans, if that makes much of a difference.
 
#5 ·
Keep in mind that if you decide to go with a 1" MML, since you run the 2.5L, there's a high probability that if you go with a poly style MML, you'll feel an increase in harmonic vibrations (even if there were none to start with).

2.5L folks get better results while using a rubber MML & far less occasion of harmonic vibs.

Whichever end of the teeter-totter you decide to alter, it will cause more stresses on the opposite end mount(s). In other words, if you raise the engine, the tranny mount gets tweaked & if it already has cracks, they will increase quickly especially if it's old & weathered.
 
#8 ·
+1

Stick with the factory motor mounts for the 2.5L - this is first hand experience. Buy the 1" MML spacer block kit that uses the factory mounts. The spacer kits are only about $50. Try this first.
If you are going offroad, you also gain 1" of clearance on your oil pan.

I personally really don't like t case drops. I understand their use in temporary situations, but I'd really recommend an SYE and CV driveshaft when you can afford it.

The t case drop also causes you to LOSE ground clearance, so again, if you are going offroad, this is counterproductive.
 
#7 ·
Yes the money tree doesn't have many leaves left on it after buying lift, tires, wheels led light bar and pods front and rear bumpers winch locking glove box locking console CB with pa locker.....hehehe first jeep so I got a little excited!!! Got to slow down on picking the leaves... Going to do the 1" tranny drop for now and fill the sye/cv fund to do it right. $2000 jeep, $4000 in upgrades and haven't even wheeled it yet. Guess I'm a jeeper now there's no turning back!
 
#9 ·
Yes the money tree doesn't have many leaves left on it after buying lift, tires, wheels led light bar and pods front and rear bumpers winch locking glove box locking console CB with pa locker.....hehehe first jeep so I got a little excited!!! Got to slow down on picking the leaves... Going to do the 1" tranny drop for now and fill the sye/cv fund to do it right. $2000 jeep, $4000 in upgrades and haven't even wheeled it yet. Guess I'm a jeeper now there's no turning back!
Funny how that happens.:grin2:
 
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