!st gen gear ratio question

[maggies man]

Wanting to buy a 1st. gen. 4x4, reg. cab 5 speed. I now own a '92 Dodge cummins 4x2 w/ 3. 56 gearing. I wouldn't want to go any lower. Did Dodge make a 1st. gen. 4x4 w/ that ratio. I think 4:10 is two low, 3. 73 is better, but a 3:56 is better still, imho. What rpm does a 4:10 ratio turn @ 70 mph, 3. 73@70mph. I don't have a tach in my '92, so I don't know what the r's are, but it sounds about 2100 or 2200 rpm's. I just want to keep the rpm's down at freeway speeds for wear and fuel economy. I cherried out a '66 ford F 250 that had a 4:10. I changed it to a 3:73, but still wasn't satisfied, so I put a 27% N. P. overdrive in it from Advance Adapters, and hit a home run. My rpm's went to about 2200 @ 70 mph. Nice cruising speed. Any info will be appreciated. Thanks in advance. Pat

 

[NIsaacs]

The 1st. gen. W250 trucks were offered with 3. 07, 3. 54, and 4. 10 with the 5spd. The W350 SRW/DRW only offered 3. 54 and 4. 10, w/5spd.

Nick

 

[Bob Beauchaine]

My '93 came with the Getrag G360 and 3. 55s in the rear diff. as original equipment. My tach showed about 1900 rpms at 65 on the freeway. Switching to the NV4500HD dropped that to under 1800 at the same speed. Towing 8000 lbs across the country the best I saw was 15. 14 and the worst was 9. 55 - towing into a 35mph head wind in Iowa - that was with the Getrag. The best mpg towing with the Getrag was 17. 94 from Portland to La Grande OR which included desert and Gabbage Hill.



Bob

 

[RWherley]

I have a D350 with a getrag and it had 4. 10 rears when i got it and it turned 2500 rpm to go 67mph, I have now change to 3. 54 gears and run 2000 rpms at 70. Not towing i have gotten a best of 23 mpg

but usely get 19. 5 to 20.

 

[maggies man]

Thanks Bob, I get about 15 mpg while pulling my 29' Airstream, 20-21 otherwise. Pat

 

[maggies man]

so I need to watch for a 4x4 w/ 3. 54 gears. Can't find a truck anyway, now this really narrows down the search. Thanks Nick

 

[maggies man]

Thats what I needed to know. 2500 @ 67mph is too high for me. thanks RWherley. Pat

 

[Simplysmn]

But you have to remember theses Motor's were made to run hard and not get hurt

 

[DVolk]

My 92 has 355s and likes to cruise at 72 mph and it gets around 23 to 25 mph empty and 14 to 16 towing

 

[maggies man]

Simplysmn, do you know what the suggested operating rpm range is?

 

[Simplysmn]

Not right off hand no but I have never had a truck with stock tires on it my last first gen was a crewcab swap to Diesel and I use to set to cruise control at 72 and that was 80 mph due to bigger tires speedo was off and the truck would run all day at that speed un and down hill's never got hot and didn't have any troubles with truck what so ever I was also running 410 gear's with 37 in tall tires .

 

[RWherley]

Right there is the key your 37in tires geared the truck up and help to give it better highway speed when mine I was running duals with 235/85 R16 that are only around 30 or 31in tall

 

[TFaucette]

correct me if i'm wrong but i tought that the 3. 07's only came in 89-91 trucks with a non overdrive 727

 

[NIsaacs]

I thought so too, but here is a clip from my '93 towing guide.



Nick

 

[TFaucette]

oh, wow that must be really rare but awesome!

 

[Bob Beauchaine]

My Tech Service manual does not show 3. 07 rear diff. as an option. It shows the following 3. 54, 3. 90, 4. 10 and 4. 56 as options. With rhe following GCWR ratings:



3. 54 = 12,000

3. 90 = 13,000

4. 10 = 13. 500

4. 56 = 14,000



Bob

 

[NIsaacs]

The 3. 90 and 4. 56 are gas engine ratios.

Nick

 

[maggies man]

I spoke with Gear Venders in El Cajon today on the phone. They told me that a 4:10 ratio with their overdrive unit will go to a 3:20 ratio, and would tach 1700 at 70 mph. That is plenty tall for me. The application in a Dodge/Cummins is a common one,which I was not surprised at all to hear. The overdrive unit would be tougher than the transmission, so its all good. Thank you guys for all the input. This is a great site. Pat