3:07 for towing

[dlefebvre]

Just joined the forum-awesome information. Between my father and I, we own 3 first generation CTD's. My father recently bought a 90 3/4 ton reg cab LE. It has only144000 km(85000miles) It has an automatic (3 speed-no overdrive) with 3:07 differential. I was wondering if this thing will be any good for towing with the "highway gears". I know that gear ratio is not much good for towing with a gas engine, but I thought that the gear ratios might be different in the 3 speed that is put behind the diesel. It will be towing a 8000# 25 foot fifth wheel. any info would be greatly appreciated.











91 350 dually, total body restoration, K@N, fiberglass box cover, 5 speed, 4:10, performance mods to start soon, chev indigo blue

 

[Philip]

As far as I know the 727 gearing is the same from the gasser trans to the diesel.



The load your talking about is the most I would want to pull with the 3:08's. If you notice I have the same gears in mine. I have pulled/hauled up to 7k with mine. If you are going to be runnning in hills that gear can kill you. Flat ground is no problem.



Make sure you do a full service on the trans before towing. Also add a second trans oil cooler if it doesn't have one on it now.



The 90 model is not intercooled. I would start looking for one. Towing you could use one. It will help when you want to turn it up for towing.



I almost forgot.



Welcome to the TDR

 

[Gary - K7GLD]

My old '91 had an automatic and the 3. 07 - and not a BIT of trouble in Sierra grades towing our 7000 lb fiver - in fact, I added a US Gear OD, and towed in OD on grades up to about 4% without need to shift into direct - and picked up 15 mph of top speed when running empty, which made cruising at 65-70 mph a "no-sweat" situation...

 

[Thierry]

My 89 has the 3. 08's and gear vendor, towing a 85 crew cab truck on a 1800 lb trailer was a breeze,

16 mpg and cruise set at 70 mph 1950 rpm, hills

were no problem just droped out of overdrive and never saw the temps come up as I have the new cross flow radiator set up.



Thierry

 

[dlefebvre]

thanks for the info guys, looks like a gear vendor is the way to go without changing diff gears and diff housing