have a 2002 36z on a mack. lost the top 4 gears. trying to save money in this economy and fix it my self. some guys say if its only the high gears i dont have to drop the trans it can be fixed from in the truck. any input i might be in over my head

First did you lose all the gears or will it just not go into high range? Which could be anything from a bad splitter to just too low air pressure. Honestly for the amount of room you have to work on it in the truck as compared to dropping it on the floor to get at it, I personally would opt for the floor model.

it goes into high range.  i had 7 and 8 when it started to go then only had 6 drove in that for about 15 miles then lost it.  now only have low range.  when i lost 6 it started to slip in and out then it just went to a grinding nose. low gears are fine shift all of them with no problems

I know the $ is a bitter subject here but here it goes.I would believe if I was trying to save I would use it in r&r of transmission,it probably has to come out anyway.I would find a reputable shop to repair with warranty.The downside is should something go wrong who would eat it?

I'd be inclined to agree with Many, handle the re & re yourself to reduce costs and locate a reasonable facility to perform the repairs.

You didn't mention Mack or Eaton tranny? Regardless, pulling a rear section to replace a failed range selector when major shrapnel has had a chance to migrate throughout the internals - leads to further trouble down stream if the front section regardless of condition is not carefully cleaned. The large magnet pucks inside the Eaton tranny case will suck up a lot of ferrous metal, but brass goes its own way. If you feel lucky, you might spend the time to pull the rear section and view the interior for metal shavings and such. If not bad then the sliding clutch collar is most likely bust up, that can be done while the front case/ clutch/ etc. remains bolted up to the engine. Reinstalling certain Eaton rear sections requires some tools to hold the countershafts in line, the roller bearings can be "bonged" when mating into their races and that ends up in another failure. Unless you're really handy or have some trained help, I'd stay away from going inside really.

Lorne

I had this ame problem with an 06 38zs it cost us almost six thousand,the truck was out of warranty by 2 months and it was the second problem with that transmission and mack wouldnt stand behind it the truck had less than 20000 miles on it,i would take the transmission to a mack dealer that way you have a leg to stand on if it doesnt last long

there is no way out of this one r/r the trans dont need to be on a big job when it lets go spend more now save latter i know it suck's but it will pay off in the long run. I bought a 32 putz from cole and lambert have it one year now had to r/r trans repowered the truck with new motor sucked a valve on job and repiped the whole truck hopefully this season all will go better good luck.

mine went 2 years ago mack dealer fixed it in 3 days $2400. worth every penny they have 6 month warranty on the tranny you dont get that with in house repairs 

mine went 2 years ago mack dealer fixed it in 3 days $2400. worth every penny they have 6 month warranty on the tranny you dont get that with in house repairs buy the way it was on a 2000 mack

I'd get on the phone and call some good trani mechanics get some free advice. Call some mack repair shops ask to talk to a their best trani mechanic, get some free advice. Usually they are good guys and will give you some good expertise. When I have tech problems I call dealers all the time, they don't know where you live.