Engine/Transmission (1998.5 - 2002) 4.10 gear swap? Yes? No?

[curatchko]

A friend is getting rid of his 2001 and has offered to allow me to swap his 4. 10 gears into my 1999 with 3. 54 gears...



I think the truck would pull my trailer much better, but I'd like to hear what others with 4. 10 gears think about them. Too much gear? I have 33 inch tires.



Also, at 70 mph, Im sitting at 2000 rpm. What will the 4. 10 gear be at?



Thanks for the help.



Chris

 

[Shovelhead]

My '99 3500 is running at 2100rpm at 65mph with Auto transmission and 4:10s but I'm still running stock tires.

The 4:10 with your 33s should be

 

[Turbo Tim 1]

With stock 235/85's and 4. 10's with a five speed I am at 2500 rpm at 75 mph and get around 18 mpg without much highway driving, it drops a little when it's all highway. As for pulling, the only thing that limits me is EGT's when I am going up a hill. I recently pulled about 8,000 lbs of tractor and equipment from Maine to New York and was glad to have the 4. 10's but I don't tow that much and would really like the 3. 54's for fuel mileage.

 

[bbsher]

Diff. gear change

I believe that if you change from 3. 54 to 4. 10 you have to change carrier also. Check with West Coast Differentials @ www.differentials.com and they can tell you. You'll find all the specs. and formulas for tire size, rpm, mph and etc. I have 3. 73's I got from them and they are doing a fine job for me.

 

[curatchko]

I don't plan on removing the ring gear from the carrier... I plan to take his carriers too. should be a quick swap.



Just don't want this to be the wrong decision.

 

[willyslover]

IMHO... only if you tow a bunch... I've had both 4. 10's and 3. 54's and PREFER 3. 54's . . and I live in the mountains where the 4. 10 are nice. .

however the equaling factor of RPM is the tire size you have... I have only had the 235's [both rigs Dually's] which are about 31"



sooooooo be preped for about 500 RPM change and feeling like you need another gear with 4. 10's

 

[ob1kobi]

Is it a 2001 OR a 2001. 5? If it is a 2001. 5 then it will have the 4 wheel disks, and antilocks. I don't think your 99 has these, only front disks, and front anti locks, if I am correct. This may cause a problem for you. I was looking at doing the same swap, but I wanted to keep my disk brakes, and it was just going to be too expensive.



Ted

 

[curatchko]

Both are drum brake rear.



The rears in a 99 aren't anti lock? I thought they were. They were in my 2500 GM with drums.

 

[ob1kobi]

curatchko,



I am not sure if they are or not. When my post was floating around, somebody mentioned it. It's just something else you may want to look into before you do it. Like I said, it just ended up being to expensive for me, so I abandoned it.



Ted

 

[dremelts]

Originally posted by curatchko

Also, at 70 mph, Im sitting at 2000 rpm. What will the 4. 10 gear be at?

I have 4. 10 gears and 265/75R16 tires. At 68 MPH I'm running about 2400 RPM. I really like the 4. 10 when I'm pulling but would sure like another gear in the transmission.

 

[tarussell]

I got 4. 10's in mine and would not want it any other way !!!! I bought a truck and I believe that trucks should be able to have a great crawl ratio and pull with ease. I still get 18 mpg. on the highway if I keep it under 75 mph w/ 265/75 R 16's. DO IT !!!!!

 

[Shovelhead]

BTW, my '99 has all wheel anti-lock brakes.

 

[drag racer]

4. 10 is the way to go with the auto trans. and you tow anything heavy, but I sure wish I had 3. 54 when running unloaded on the highway. It kind of sucks having the motor scream at 80-85 mph, and the lower mileage. Overall, I give the nod to 4. 10, but it depends on your specific situation.

 

[RADdodge]

Curatchko – I have a spreadsheet that calculates this sort of thing and a 285/75R16 tire (32. 83” diameter) calculates to about 1750 rpm at 70 mph with 3. 54 gearing. Tire sizes never seem to calc exactly, but I’m off a lot here. Could be wrong, but it has been very close so far. My question, is your speed really 70 mph? It looks like you’re really running 80 mph at 2000 rpm! 4. 10 gearing should net you 69 mph. If you compare stock 235/85R16 tires with 3. 54 gearing to 285/75R16 tires with 4. 10 ratio, the resultant ratio calculates to 3. 96. 4. 10 gearing allows you to successfully use larger tires.

 

[NVR FNSH]

2000 RPM gives me 66mph according to my GPS - see sig for truck specs. If I wasn't towing a 36ft 5th wheel I'd prefer the 3. 54s. BTW - I've never gotten better than 17. 5 mpg.



Brian

 

[curatchko]

What kind of mileage are you guys getting with the 4. 10 gear while towing? I seem to get around 12-13 mpg lately while towing 11000 pounds. Granted, my foot is buried in the pedal pretty hard most of the time... .

which is why I though the 4. 10 would be good.

 

[dremelts]

curatchko, 10-13 is about what I get towing and I'm not towing as heavy as you are. Your numbers sound about right.

 

[NVR FNSH]

I get 10mpg towing but my biggest problem is frontal area. My trailer is spring-over axle to clear the bed rails and the front bedroom is an 'almost' stand-up room. IOW - very high profile.



Brian

 

[Snow man]

Id go for it,i have the auto w/ 4. 10 's. I also have 285 tires,i tach at 2100 @ 70 mph,perfect IMO. Dont go by the guys with standard trannys,there OD is not as tall as the auto's,they tach about 150-200RPM's more than us auto guys do . ,combine that with taller tires,and there is a big difference between 2200 at 75 in my truck and 2500 at 75 with a 5/6 speed,and stock tires.

 

[drag racer]

Towing my 28' enclosed ~9,000, fairly flat terrain, A/C on, 65-75 mph, I get 12-13 mpg pretty consistently. Seems to correlate pretty good with prior posts.