RPM and speed for 4:10s

[johnwen1]

Hey everyone,

I need some info from all you folks with 4:10 gears and an automatic transmission. I just made the switch from 3:54 gears to the 4:10s and my rpm went way up and my speed went way down. It's quick though!! 0 to 40 mph in a heartbeat!! I did it for more pulling power, but something is just not right. So, what's your rpm at 60 mph and 70 mph so I can make a comparison. Thanks.

------------------
Wendell

 

[Dennis Garrett]

I think mine is about 2050 rpm at 70 with 3:54's, but you have to figure in speedo error, & wonder about tachometer error at the same time. I always heard there is about a 200 rpm difference in the two rear ends. Also of course, tire size makes a difference.

 

[Scollins]

I run 67 MPH (per GPS) at 2000 rpm with 4. 10's and 285/75r16 tires in overdrive. I haven't really looked at speed at other rpms too much. I have a long trip to drive tonight, so maybe I'll see what I do at 2125 and 2250 rpm. My "effective" ratio is 3. 8 due to the larger tires.

------------------
Scott Collins
'98 Ram 2500 4x4 12 Valve Cummins. Slightly BOMBed! #ad

Renton, WA

[This message has been edited by Scollins (edited 02-28-2001). ]

 

[Cooker]

Tire size is also a big factor here. The larger the tire the slower the motor.

Here are some calculated numbers for you on the differences (lets assume we have a 265/75/16 tire and with a on the truck height of 31", also these numbers are in overdrive of . 7 if I remember correctly)
3. 54 4. 10
70mph 1880 2175
75mph 2015 2330

If you are running 285/75/16 (lets say 32. 5" tall)
3. 54 4. 10
70mph 1790 2075
75mph 1920 2225

Obviously real world numbers will be different when factoring in variables such as tire size. Two 285/75/16 tires of different manufactires will not necessarily be the exact same height. The tire pressue will have a slight impact on the numbers. Also the weight of the truck will have a little effect, and headwind if any. These factors may seem insignificant, but ever little item adds up to 50 - 100 RPMs. For these reason I think the calculated numbers are as just as good as real world.

I hope this helps,
Ryan

I've been thinking about the switch myself. How did you go about it and could you comment on cost? Thanks.

 

[johnwen1]

Thanks everyone for your replies. Most helpful.

Ryan,

I for one don't recommend switching to the 4:10. I made the switch for better towing capability and then just 3 days later got my 99 3500 QC with 3:54 gears behind an auto transmission. I still use my 94 2500 automatic for daily commuting. I'm definitely going to put my 3:54 gears back into the 94.
Since day one something has not been right about the 94. I was running with a friend and he said we were doing 60 mph and my tach registered 2300 rpm. She was really humming and it, in my opinion, would probably top out at 75 mph.
The cost to do the switch was not bad at all. The ring and pinion set was about 300. 00 and labor to install was 200. 00.
By the way, the tires on the 94 are 245/75 with 16 in rims. If you decide to make the switch let me know how it turns out.



------------------
Wendell

 

[johnwen1]

Ryan,

By the way, I'm ordering a PE EZ for my 99 3500 QC 24V, 3:54, AT and also changing all fluids, engine, transmission, and rear-end, over to Amsoil synthetic. I feel better about it pulling my new fiver now!!


------------------
Wendell

 

[BigYellowIron]

I run about 1850 at 65 mph with my 4. 10 in OD with 265/75/16. 2000 at 70mph
adam

------------------
"POWERSTROKE THIS"
Adam Harman
95 auto red and white #6 tst , eagle alluminum wheels. Stright pipe, Still BOMBING

 

[Black Fingernails]

I have a 4. 10 and am thinking about putting in a 3. 7 It seems like good middle ground. Higher top end speed but still good for pulling and initial accel. Any comments?

 

[chrgr446]

I too have 4. 10 gear. I put the gov. spring kit in and went from 84 mph to around 110mph.
BIG improvement!!!!!!!!!!!
Now figure in the Gear Vendors overdrive could I see 130+ in my future?

 

[johnwen1]

BF

I don't know what model your is truck is, but there were only 2 options for my 94 and that was 4:10 or 4:88. The 3:73 was not available and that's what I wanted but had to opt for the 4:10s. It's all a mute point now though because I'm going back to the 3:54s.

Wendell

------------------
99 QC 3500, Automatic, 3:54 Gears, "Big Ole White Truck", Chrome bed rails, Nerf Bars, Billet aluminum grill and fog light openings, stainless bug shield and eyebrows, billet aluminum "RAM" third brake cover. Amsoiled.

 

[sewman]

If you want something like a 3. 70 ratio tires 3" taller would give you that ratio,
cheaper than gears if you can get them on your truck.


------------------
94,4x,#4TST 16cm. ,5spd,4. 10LSD,35"BFG A-T,Bushwacker Flares , A-PIllarGuages,Southbend clutch,straight ex. ,RS9000.