The 379 that has taken root in one of my shop bays has a interesting problem. The guys yesterday went to reinstall the driveline and couldn't get it in. Too tight between trans and rear axles, driveline too long. I looked at it and we put air to the bags and got in installed, but I don't know how this set up worked before. It had to be pushing real hard on the trans and front bearing in the rear diff, because the driveline was completely collapsed in the slip portion, and actually was almost putting pressure on the trans and rear when the bags were down. So I sent one of the guys today to the driveline shop, they said no need to bother shortening the one we have, its like 75" long, and they said it would twist it right up with a load. I thought it was kind of different that it didn't have a carrier bearing in it when the guys had trouble reinstalling it, but I didn't really put two and two together until the driveline guy said something. There is no carrier bearing between trans and front diff. Just one long driveline. Why would the previous owners have removed the carrier bearing and the two piece driveline, and had a extra long driveline made for it? As tight as it was collapsed, I can't see how it didn't destroy itself or something on one end or the other. I bought the truck last winter with a blown motor and have no history on the truck, we just loaded it on a trailer and hauled it home. I sent my mechanic from the driveline shop to the truck junkyard, and he picked up a set of drivelines and carrier bearing bracket, so its going back in how it should be, I was just wondering if anyone had a idea why they may have had it put together that way. Old driveline is on the right, the new/used set up is on the left, we'll have to measure it all out and get that set up cut down.
Did you drive it after you bought it? I had one too long before, on Century! When suspension was going Up and down the transmission made a noise as it was ready to come apart. Ex Gordon’s truck, don’t know how they drove that thing. Shortened drive line 2” and it still running around, it was back in ‘04 at 730000 miles! But transmission making noises now because it has 1860000 miles on it, and Rockwell’s generally noisy!
No driving after I bought it, I bought it with a dusted motor in it. We've put a different engine in it now, and are trying to sort out the other issues.
Just to be sure I understand what the drive-line guy was saying. He meant that the drive shaft was going to fail the first time you put a good load of torque into the shaft? Or was he saying the shaft would "self adjust" for the proper length kind of like a crush washer used on some pinion shafts!
I think the driveline guy was stating the shaft was at the max length it could be or slightly over and not able to hold the torque due to the length. Attached is the Dana guide for driveshaft length. I would be curious what the truck came with from factory. I wonder if the axles were slid up and the frame shortened. Last six of VIN?
Driveline man said we were past max driveline length. He said max was 72", and was concerned about twist under load. There is a crossmember where I can mount the carrier bearing. We had to put air to the suspension, to get enough distance between trans and front diff to install the old driveline. With the bags deflated, the slip portion was completely bottomed out on the plastic sleeve, and the other end of the slip drive inner was actually extending into the ujoint area. 1992 Peterbilt 379, last six of vin is 313064 Its currently day cab.
This is a picture of when I loaded it up and hauled it home. I cut the tips of the stacks off to get under legal height, they were rusted out so no loss. I've got most of the exhaust patched and/or replaced, still waiting on a y-pipe. 3406-b, 9 speed, if I remember right like 4.33 rears on 24" rubber. Another thing I'm fixing- the right rear hub is budd, everything else on the truck is hub pilot. I'm guessing they ruined a hub and must have had a hub off a different axle that would fit, I'm going to get a hub pilot one so at least they are all the same. The original engine was ruined by never changing air filter, or the gaskets where the top fits on the cans. The insides of the whole intake system was filled with soot/grime, I'm guessing feed mill/ quarry or end dump- dirty conditions.
Yes it is over length 72" is a standard for max length but we had 22 gliders running 76" front shafts from trans to center bearing. Never lost one but those were thick wall tubes too. Truck Shop
How many tractor trucks 20 or less years old have one piece drive lines? There is one at work i cant remember witch one but it has is one piece.I know about the 72 inch rule but i havnt ever checked it. Its doesnt have a short WB.
Truck was sold out of mississippi. 4.33 rears Looks like it only had a single main driveshaft from factory. P/N 810653-5931 Spicer online breaks the shaft down as follows: So i wonder why it is so tight? Trans been replaced? Factory is RTO-14609B
Current one is like 75" and we were going to cut 2" out of it, so that would get close to factory spec. Driveline man said 72" was "as long as I can legally make it". Maybe they twisted one up and had to make one on a "best guess" length and made it too long? I don't have a exact measurement on the driveline, we were just going to make it 2" shorter than it currently is, to give us some compression room, until the driveline man said that was too long. Transmission has been replaced with a reman, but its still a 9 speed. Thanks for the info pushbroom.
Bought one new. Identical tractor except had 13 spd never paid attention to fact it had 1 piece driveline. Never had a problem for the years I owned it. Used it as a lowboy tractor pulled loads over 100000 regularly. I always did wonder about that though!