Need advice on axle ratio

[photog]

I'm running a 2500 long bed with AT and 3. 54 LSD. I do a lot of towing with an 11000# trailer. Everything is great when I'm running in Florida on flat roads but when I get in the mtns I really notice the "mis gearing". If you read my bio you'll see that I've done some work on the engine and AT. That has helped a lot but I'm seriously considering changing the axle ratio to 4. 10 to 'unload' the AT a little. I have a bunch of questions and I would really appreciate some constructive advice.

1 Can I reuse my current differential and just change the ring and pinion?

2 Do I have to recalibrate the speedometer?

3 Is it better to get gears from DC or from an aftermarket company? Anyone care to recommend a good gear supplier?

4 Will I need to adjust the transmission shift points to match the new rear end?

5 Are there any problems with the PCM or ECM caused by a gear ratio change?

6 Are there any other issues that I should be aware of?



Related questions:

1 What is the load limit of a Dana 70? I know the Dana 80 is 8000#. Is the Dana 70 7000#???

2 What is the load limit of the wheels (16X6. 5 chrome)??



Any help or advice you guys can offer would be greatly appreciated.

Thanks...

 

[csutton7]

here's some answers--



1) yes

2) probably--if it can even be done--you may have to buy one of those calibrating boxes to add to the truck

3) aftermarket

4) shouldn't

5) no

6) I don't think so



1 & 2--I don't know





chris

 

[pwr2tow]

You will need to change out the carrier because of the difference betwee the 3:54 and the 4:10's. IF you have a dealer do it, it will cost approxiamatly $2,400 for a 4X4. If you want to change gear ratios the better choice might be 3:73 or 3:90 these will fit rite into your existing carrier. I had a previous truck done this way and it cost me $800 for a 2 wheel drive. You might want to check prices for gears at Randys ring and pinion.



Ron

 

[Steve Campbell]

Not trying to be funny, but how about the addition of a VA or EZ. With more power, you should be able to get by nicely and not have to go the expensive re-gearing route.

 

[Devildog]

I recommend larger injecters and a EZ or a comp box also, You'll be very happy and not have to go through all that other stuff.

 

[csutton7]

ronsram--you're right--I forgot about the carrier-thanks----chris

 

[Mallory]

If you need a carrier your limited slip is going with it I believe.

 

[jimnance]

You may want to check prices on the diff work. I added the EZ and exhaust system, but like you on the hills with 11,000 lbs I'm down in second gear with 3. 54's, I'm changing to 4. 10's and our local 4X4 shop quoted $1,400 for front and rear including parts (Spicer) and labor.



Diff's are one of their specialities so I am sure they know what it involves.



I know I'm going to lose that nice sweet RPM and fuel mileage I enjoyed with the 3. 54's when empty, but I'm pretty sure I'll be able to pull the hills with the new gears in third gear at better speed. Also, acceleration should improve.



If the RPM's when driving unloaded drive me crazy I may consider larger wheels and tires when not loaded. Could have got one of the gear vendor units with shift on the fly over/under drive, but that is $3,500. 00.

 

[Steve M]

Be careful what you wish for. I had a '95 auto/3. 54. Traded for a '98 12v 5spd/4. 10. Good for towing but had to slow down too much to shift to direct. It was also tiring to listen to it howl all day towing. It was irritatiing to hear it howl running empty and wishing I could just shift one more time to drop the rpm. Traded it with 89k for another auto/3. 55. I can drop to direct at 65mph without slowing down. I have O/D for towing on the flats and it's very quiet. I like the performance of the 4. 10 while in O/D but overall I like the 3. 55 better.

 

[Shooter]

3:73's or 3:90's



Increasing power with out taking some load off the engine will just make higher exh temps.

How do I know??? I have a gear Vendors that puts me at 2200 rpm in direct GV od. Sweet for towing at 75 mph I would really like another 200, considering 3:73's to acomplish that.

 

[csutton7]

I don't think you can get those gears--4. 10s is your next choice---anyway that's what I was told last year when I did my swap---chris