2:91 or 3:55?

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TrailBeast

TrailBeast

AKA Mopars4us on Youtube
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I have both, but the 2:91 are in the assembled sure grip rear end and ready to go.
The 3:55 are in like new condition, but I would have to buy new pinion bearings and a new seal. (about 50 bucks) and set the rear end all back up again.
The rear end is an original 1974 8.25 with a Jeep Cherokee disc brake setup added.
The car is a daily driver, and spends about 75% of it's time under 55mph with 1-2 times a month at 75-80 for a few hours.

Every time I think I have made up my mind I hesitate again, which is really unusual for me.
What would you do, and why?

Thanks
 
well, you have OD I believe, which makes the 3.55's perhaps the right choice. With a 904 or 727, I like 2.9 gear for the highways.
 
Put the 3: 55 then you know you want to, you know you've been talking about it, just pull the trigger...
I love my 355 just now and you have the overdrive as well so you are completely covered..
Time to start enjoying those spirited takeoffs...
:thumbsup:... My-2....
 
TrailBeast said:
I have both, but the 2:91 are in the assembled sure grip rear end and ready to go.
The 3:55 are in like new condition, but I would have to buy new pinion bearings and a new seal. (about 50 bucks) and set the rear end all back up again.
The rear end is an original 1974 8.25 with a Jeep Cherokee disc brake setup added.
The car is a daily driver, and spends about 75% of it's time under 55mph with 1-2 times a month at 75-80 for a few hours.

Every time I think I have made up my mind I hesitate again, which is really unusual for me.
What would you do, and why?

Thanks
Click to expand...
I think it mainly depends upon where the torque of the motor is in the rpm range.
If the motor/torque can handle the 2.91 from a dead stop go with those.
If the motor needs some help pulling away from a dead stop go with the 3:55's
 
my68barracuda said:
I think it mainly depends upon where the torque of the motor is in the rpm range.
If the motor/torque can handle the 2.91 from a dead stop go with those.
If the motor needs some help pulling away from a dead stop go with the 3:55's
Click to expand...
Agree, it's in the motor. I know somebody that has a 360 with 2.94's and it cuts better 60 ft times than another guy i know with 3.54 gears and a 410. Motor plays a big part.
 
What car is that Jeep rear end in and what is your motor?
The easiest and most economical install would be the 2.9's...so try them.
 
318willrun said:
Agree, it's in the motor. I know somebody that has a 360 with 2.94's and it cuts better 60 ft times than another guy i know with 3.54 gears and a 410. Motor plays a big part.
Click to expand...
can't you keep this on your summer race or your ketchup thread and not just trash everybody's threads...
 
my68barracuda said:
I think it mainly depends upon where the torque of the motor is in the rpm range.
If the motor/torque can handle the 2.91 from a dead stop go with those.
If the motor needs some help pulling away from a dead stop go with the 3:55's
Click to expand...

The low first of the RH trans gives me plenty of takeoff, but the car just feels kind of like it's barely running above the converter stall in the higher gears.
Kind of "rubber bandish" feeling if that makes any sense.
It normally runs in the 2,100 to 2,500 range in the every day driving.
(fuel economy is a secondary)
 
j par said:
can't you keep this on your summer race or your ketchup thread and not just trash everybody's threads...
Click to expand...
??? my68barracuda made a good point about the torque of the motor, so I just gave an example of a couple guys I know that went along with what he stated. Might help the OP decide, I think he has a 360 magnum, so something to consider...
 
TrailBeast said:
The low first of the RH trans gives me plenty of takeoff, but the car just feels kind of like it's barely running above the converter stall in the higher gears.
Kind of "rubber bandish" feeling if that makes any sense.
It normally runs in the 2,100 to 2,500 range in the every day driving.
(fuel economy is a secondary)
Click to expand...
what gear is in the car now?
 
318willrun said:
??? my68barracuda made a good point about the torque of the motor, so I just gave an example of a couple guys I know that went along with what he stated. Might help the OP decide, I think he has a 360 magnum, so something to consider...
Click to expand...
You were kicking my sand castle and you damn well know it...
My deepest apologies Trail Beast I will not post no matter what he says next...
 
ir3333 said:
What car is that Jeep rear end in and what is your motor?
The easiest and most economical install would be the 2.9's...so try them.
Click to expand...

The rear came out of another Dart and is original A body.
The motor is a 9.1 mild 5.9 Magnum with a 214/224 cam and 1,800 converter.
Basically built for torque.
 
318willrun said:
I just went from 2.76 to 2.94. Barely a change as I already knew, but I could tell. I believe it was about a 2-3 mph difference in the speedometer.
Click to expand...

My speedo reads about 7mph slow, so any change in the gears will just make it closer.:D
I will be keeping the bearings on the current pinion in either case, so it will be fairly easy to change it if I don't like it.
 
I hated 3.9's and 3.5's but love my 3.23's.I'm going to try 2.94's next summer.
From 2.73 to 2.94 will be noticeable with the low first and second gear trans. Cruz will be great with the 2.9's and i think you'll love them.
 
TrailBeast said:
My speedo reads about 7mph slow, so any change in the gears will just make it closer.:D
I will be keeping the bearings on the current pinion in either case, so it will be fairly easy to change it if I don't like it.
Click to expand...
Remember I'm telling you exactly what you want to hear! Go for it! LOL...
 
ir3333 said:
I hated 3.9's and 3.5's but love my 3.23's.I'm going to try 2.94's next summer.
From 2.76 to 2.94 will be noticeable with the low first and second gear trans. Cruz will be great with the 2.9's and i think you'll love them.
Click to expand...
Do you have an overdrive with lock up converter as well?...
 
I got to go now as I have to take the axles over to a friends house to put the new longer studs in them.
Gotta let others feel involved you know.:D
 
904 with the 2.74 and 1.54 first and second gears from a later trans but not lock up.
2400 stall 26" tire small cam 340 Dart.
 
ir3333 said:
904 with the 2.74 and 1.54 first and second gears from a later trans but not lock up.
2400 stall 26" tire small cam 340 Dart.
Click to expand...
I think that's where I'm making the suggestion being as he does have a 4-speed lock up converter transmission. The kind of changes the game a little bit I think?...
 
318willrun said:
I just went from 2.76 to 2.94. Barely a change as I already knew, but I could tell. I believe it was about a 2-3 mph difference in the speedometer.
Click to expand...
Did you change the speedo gear ? I went from 3.23 - 4.56 and man my speedo really showed some speed. lol
 
fishmens67 said:
Did you change the speedo gear ? I went from 3.23 - 4.56 and man my speedo really showed some speed. lol
Click to expand...
no. my gear was set for 3.23's, so my speedometer still lags behind, obviously the faster the more it's off. When mine shows 51 mph I'm actually doing 55 mph. I always check with GPS
 
spends about 75% of it's time under 55mph with 1-2 times a month at 75-80 for a few hours.

without getting into some serious tire swapping, the effect of the gear change on the vehicles pull away will come down to a gut decision.
However you can simulate the engine noise / car feel with the gear options. Use one of the online gear ratio / rpm calculators to determine the engine rpm at say 55 mph and at 75 to 80 mph with your existing tire size. Then perhaps using a lower gear in the transmission hit that engine rpm in highway conditions for each gear set. You won't be doing the actual MPH that you listed, but the engine will be spinning like it was, so you can get a feel for it.
 
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