rear end gearing

[odee]

Guys I have driven my 85 gmc dually swap for about a year now. Have towed the jeep and sandrail with it plus a full size chevy 4x4 truck. My truck runs a 89 6bt and getrag, have turbo off of a 02 with exhaust brake, intercooler from a 98 my rear gear is a 4. 10 running a 235-85-16 tire. Wanting to get somemore highway speed out of the combo. Which rear gear ratio would you guys want to have in the truck? thanks

 

[HBarlow]

Your only choice if you use OEM parts will be a 3. 54 which will give you greater top speed but sacrifice load startability if you're towing heavy. Aftermarket manufacturers may offer other gear choices but the OEM differentials were 4. 10 or 3. 54.

 

[odee]

I'm trying to stay away from a total rebuild of the rearend housing. Gm used a 3. 73 and 3. 42 rear gear sets the 3. 42 being somewhat rare, I don't think that the 3. 73 will give me the rpm drop for the money spent. Haven't really had time to check into the spring perch width or overall width of the dodge dually rears. thanks

 

[HBarlow]

Oops. I see I overlooked the fact that the Cummins engine is in a GM chassis. Too early in the am and my coffee had not awakened my few remaining brain cells yet.

 

[NIsaacs]

Does your GM have a Dana or 14 bolt? If it is a 14 bolt, keep it, it is a good axle and is easy to change gears in. I like 3. 50 gears with the short overdrive Getrag.



Nick

 

[odee]

the truck has a dana 70hd in it, I was told at the wrong time the the two dodges I took apart for this build that the rear gears would not work in my housing. I later found out that they would with the right bearing kit for my housing. I just don't really want to put the 3. 42 under the truck to have to pull it out to go to the 3. 54 or 3. 73.

 

[JR]

My opinion would be to go to the 3. 73 if you dont like the 4. 10. I have 3. 54 in my truck and they are great for empty driving but towing anything over 7 or 8k I wish I had a lower gear.

 

[Simplysmn]

Why not run a bigger tire ? I am running 410's with 37's and did Great on first run towing

 

[odee]

truck is a 2wd, bigger tire = spacers so the rear duals won't rub. I just got a parts truck that happened to be a crew dually also, so yesterday before I got started in the shop for the evening I pulled the cover. I had left one bolt in to find a tag on it but cover had glue on the edge so it had been off. The tag read 41-11, got inside to check the ring gear found the same number so I guess I'm in business. Thanks again for the help.