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Hey guys, lets talk good old heavy duty transmissions, such as a new process 435, borg warner t98 t18 & t19, as well as the muncie transmissions. They seem to hold a lot of similarities as far as being heavy duty, well built, top loaded transmissions. I am currently studing at a technical school to become a heavy duty truck mechanic, but on the side I love learning this stuff about old classing 1/2 ton up to 1 ton and beond trucks. First I was going through and redoing eaton roadranger 10 speed conventional twin countershaft transmissions. I found them to be a joy to diagnois their problems, dissemble and reasemble. First off, how hard is it to rebuild these old transmissions? With a press, a trans jack and some other parts would I be able to do these my self with more experience? How hard or easy are these? What do the terms "top loaded" or "side loaded" refer to? From what I've gathed its how they are assembled together and a top loaded trans is built for towing and hauling and is built tougher. A top loaded is a heavy duty and a side loaded is a light duty. But is this true?? Is it best to use a 80w 90 type mineral based gear oil in these trans listed above? Any help appreciated.
Well, I wasn't planning to rebuild these for money, it was more of for my self and a hobby. If my car or truck needs to be fixed I will diagnois whats wrong with it, and find out how to repair it the right way. I try to avoid taking it the garage at all cost of course. So in the same case for my old trucks, I would like to repair, and or rebuild these old transmissions and was wondering how hard or easy it is. Thanks for the info on the top loaded vs side loaded. It seems to be where the parts are inserted. Also im finding that heavy duty transmissions almost always use 50 weight to 90 weight gear oil where as the light duty transmissions built with lighter bearings and parts, higher gear ratios, etc seem to use atf, 10w30 etc. This is some good information on motive gear. Does anyone rebuild these transmissions themselves?
There are a few "I rebuilt it..." threads here for manual transmissions. Some, like the ZF, require some gear pullers iirc, but the older 4 speed boxes are probably pretty easy compared to a rear axle set up or certainly an automatic. As for oil, I think you got it right. Most older boxes use the 80-90 or similar oil.
Some info here on oils, beware you should do further (non-wiki) research if you get into a "it really matters" situation:
I've double checked now, because on one website it said that the new process 435 took 80w90 gear oil, and the others said that it took 50w. It appears that it acually calls by ford books, and other sites for 50w. Theres a lot of people that use 80w90 and i suppose that would work as long as the parts in the transmission were pretty wore out. But, it sounds like from what i have read it is better to use 50w especially in the cold weather. Now, are they calling for 50 weight gear oil, or engine oil? Is a weight rating from an engine oil close to or the same as the viscosity of a gear oil? For exaple is a 50w gear oil about the same viscosity rating as 50w engine oil or no? t98's t18's and t-19's and older muncie transmissions (pre-1989) all take 80w90 gear oil. The fz transmissions call for synthetic atf, but i read people using synthetic engine oils...
I rebuilt a T98 from a FC170 Jeep approx 28 years ago. Big punch to knock out the cluster gear shaft, huge snap rings, loose rollers and the normal input and output ball bearings.
When I reassembled, I used a fake shafts made from stiff foam rubber to place the rollers inside the cluster gear as an example. Pushed the real shaft in which crushed the foam down, pulled the foam out a little and repaeted until the shaft was all the way in. That one ran great for years.
I got another vehicle with a T98A and the guy said the trans was starting to make noise. On the drive home, the truck suddenly shuddered and all I was left with was high gear. When I pulled it apart, I found one of the huge snap rings had broke allowing the largest slider gear (Granny I think) to shift and the huge loose rollers came out. The shudder was when a 5/16 diameter X 1 1/2 inch long rollers went between the cluster gear and input shaft gear teeth. Sold the whole transmission for scrap iron price. I didn't even want to trust the case to not be sprung.
pretty cool information. The t98 seems to be the transmission that came before the t-18. They both share the same top cover. Its best way to tell weather its a t-18 or 98. I drove a early 70's ford years ago that must of had a early t-18 style because reverse was over to the top left side. I also drove a 1948 ford truck. That was amazing! Reverse was over to the top right in that as well. Apparently till about 1953 or so, ford used non- syncronized transmissions. I think that double clutching and being able to drive a non- syncronized trans is great! I need to get a lot more firmilar with them. But I know double clutching helps with syncronizing the speed of gears in the transmission to the speed of the engine. Im not a huge fan of slip shifting. Its just cheep. Theres a clutch pedal there for a reason duh! Slip shifting is rough on a non- syncronized but I really hate when people slip shift a fully syncronized transmission for no apparent reason. They might think that they are hot stuff because they have the skill to do it, but yet they are not using the clutch for what its for. The clutch is to break torque and release all the tention of the transmission and driveline. Instead you just fight the syncro's and break things. The only time i have slip shifted was to get home when i had the clutch go out of one of my vehicles, so I know i can do it just fine as well. But there is no point to do it otherwise. I got to drive over to my girlfriends house last night and identify her dads 1979 chevy truck transmission. Its a muncie 465 made here in muncie indiana. Another great heavy duty transmission.
Thanks for the reply. Have you ever rebuilt these transmissions? Its becoming a hobby for me to become interested in rebuilding these. When not driving from stop light to stop light in the city i highly prefer a heavy duty manual transmission. You see i do not like the un-needed wear on cluch materials and clutch parts. Im just very suprized by the few responces i have recieved. For a work truck i love having a heavy duty five speed or four speed. I love the idea's of low gear ratios helping you get more power to the wheels and ultimate control of the vehicle. Im just wondering how complex it is to rebuild these and diagnois problems assoisated with them.
Both of my factory manual-equipped trucks called for 50wt motor oil, one was a T18 and the other an NP435. Motor oil back then was different than now, so I ran synthetic 50wt transmission oil in the one, the other I didn't get enough miles to change the fluid before the engine let go.
Real trucks have the key on the left FTE Guidelines
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