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Gear change on 78 cj5


 
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Old78-5
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Joined: 18 Oct 2009

PostPosted: Sun Oct 18, 2009 12:48 pm    Post subject: Gear change on 78 cj5 Reply with quote

I recently had my gears changed in the front and rear differentials from 3:54(stock) to 4:10.
I have 33 inch tires on the jeep.
After the change, I noticed when going from first to second gear there is a vibration that seems to resonate through the exhaust making it sound louder than it used to. Also, when I let off on the throttle, the jeep slows itself down, like it's being held back. It used to roll much easier on it's own in neutral, now there seems to be a resistance and won't roll. My gas mileage seems worse.

Is this normal after a gear change?
Are the new gears so tight that they need a break in period?
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TJ Apex
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Joined: 29 Jul 2005
Location: Mountains of SoCal. 6257 elev.

PostPosted: Sun Oct 18, 2009 8:04 pm    Post subject: Reply with quote

The vibration is most likely due to the gears not being set correctly. There are shims that adjust lash, it's not easy to set and takes special tools to do it. It also doesn't take much to be out of spec.
I wouldn't drive it to much, the gears are not meshing correctly and could over heat your ring and pinion and could make things even worse.

As far as how your jeep drives with lower gears, that's typical for it to slow down quicker by it's self while in gear, but it should coast the same as before if your in neutral, again, this may be due to the gears not be set correctly.
Gas mileage will suffer simply because you are slowing down your odometer and your speedo, plus your engine is turning higher RPMs, and again gears not being set right will adversely affect MPG.

After you get the gearing fixed, buy or borrow a GPS (even a cheap one will do) and check your speedo and odometer to see how far off they are, you can even do a MPG check.

Good luck to you.
_________________
2002 Wrangler Apex
Why do I have to press one for English?!
Welfare recipients should pass a drug test to get paid…

02' Apex Edition,
2" BB, 31" BFG AT's
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Old78-5
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Joined: 18 Oct 2009

PostPosted: Mon Oct 19, 2009 5:39 am    Post subject: Gear change on 78 cj5 Reply with quote

Thanks for the advice, TJ Apex. I knew it just didn''t seem the way it should be.
I will go back and get it checked out.
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TJ Apex
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Joined: 29 Jul 2005
Location: Mountains of SoCal. 6257 elev.

PostPosted: Mon Oct 19, 2009 9:58 am    Post subject: Reply with quote

No problem..... Wink
_________________
2002 Wrangler Apex
Why do I have to press one for English?!
Welfare recipients should pass a drug test to get paid…

02' Apex Edition,
2" BB, 31" BFG AT's
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