a25c transmission problems

hey everyone we picked this nice truck volvo a25c that the trans wont shift if anybody can point me to the rigth direction i will apreciate it, i already adjusted the load sensor found some burned fuses and and non workin relays also a engine speed sensor that i like to know specs on it see if still good previous owner changed the computer per volvo mechanic as of rigth now im hunting for the transmission speed sensor any info will be preciated thanks in advance

I recently replaced the trans speed sensor in my a25c. Attached is diagram, there are two different parts determined by serial number. Either 27 or 27A in the diagram. Mine was 27a held in by a t27 long bolt. It was a bear to change basically in a blind hole. If you crawl under the truck, the sensor cover is about 10-12 inches above and just forward of the front axle. Transmission fluid bath to enjoy once you remove the cover plug, be ready with catch can. Picture of part box included. Should ohm 1000k ish

Thank you sr i really appreciate your info and the kindness of the part number and diagram i have been workin on this thing tracing wires and its been a learning experience

well done did put the pan back found the speed sensor thanks to 02silver sensor is good, done did adjust the gas pedal sensor, still this thang is not wanting to shift gears... any ideas where else to look for ?

Hate to say it but you may be going down the same path I did. I had similar issues and replaced sensors etc but in the end I had to replace the transmission....

Yea seems that way unfortunately...

Check out these posts to see what I went through. A25C Trans replacement Started on the trans replacement on my A25 this weekend. Bit of work for certain. Some takeaways for those who have not done this: - Fuel lines on my truck were similar to airbrake hose from the tank and then to a adapter fitting to some type of metric flare. I had problems finding plugs so... www.heavyequipmentforums.com New to me A25C Picked up a 1997 A25C SN 5350V9574 at auction and it seems to have the typical age related issues. Just got it to my yard today, drove it around for a bit, and it upshifts/down shifts through forward gears but when backing up if you are fwd-reversing a couple times eventually it will not engage... www.heavyequipmentforums.com

Yea i have read all the post about the transmission on this thing it have its fair amount of doctoring in it

success! ...well kind of.. i did a lot of tracing on the wiring found a burn diode, burned most relays i found oil on the transmission plug i cleaned it, i did clean the pcb board and it does shift now but it does goes to neutral after its done shift thru all gears 2-3 times and if i turn it off and on it does reset it what can it be any ideas

bender34 said: success! ...well kind of.. i did a lot of tracing on the wiring found a burn diode, burned most relays i found oil on the transmission plug i cleaned it, i did clean the pcb board and it does shift now but it does goes to neutral after its done shift thru all gears 2-3 times and if i turn it off and on it does reset it what can it be any ideas Click to expand... What did you end up figuring out, mine was running fine and then stopped moving, can shut off and restart and will go through gears but once stop I have to do it again, did pin test yesterday and ohmed various sensors, found a bad wire to load sensor but wasn’t bad enough to be issue.

My company just bought an A25C articulated truck with a water tank instead of a dump bed, the interior looks like something out of mad max. They want to semi restore this truck, the truck has no brakes and 3 bad wheel seals (it appears). I know absolutely know nothing about these machines and the main problem is if you shift into 3 the truck only goes 5mph max no matter what gear you select.

You may want to check and see if the ECU has been bypassed. See below:

Does not appear to be

Do you have the Contronic display? It is located on the upper headliner top left. If so you can scroll through and see if the gear position changes, what rom the ECU is reading etc which is helpful for diagnostics.

wish it did, appears the display has been removed from machine.

Gah, you are in tough my friend. First thing you should do if you want to try and fix without bringing in the dealer or a contract mechanic is to get the operation manual and the repair manual. Both are super valuable when working on these old war horses. The repair manual will show you how to fix the rear seals and trouble shoot the brakes as well.

yeah i down loaded a service manual with 7000 pages lol, hard to scroll through and find specific stuff but im in deep with this one.