Mack TRDL 1070- TRTX 1070 transmission HELP

[mimscorp]

Hi, I'm having a problem with my 1988 R model not shifting into high range and sometimes rev. At one point it wouldn't go into reverse unless I pumped the brakes to lower the air pressure. I then installed a small regulator on the shift handle, however, it still doesn't always shift right. My question is this: is there an air cylinder that can be replaced without pulling the trans out of the truck? One guy told me there was one on top of the gearbox and I sinply needed to jack the cab up and replace the unit. Any help would be greatly appreciated. Bill M

[Rob]

Pretty close to correct. The rear of the top of the transmission has a pair of air shift cylinders integral to the cover. Raise the cab rear if needed and remove the bolts retaining this cover. Lift the cover and stub forks from the truck and rebuild on the bench. A rebuild kit from PAI is about $20.00 and go through the "Selectair" valve on the shift handle also. The regulator pressure should be around 65psi for those transmissions. Don't kick it up or it's hard on shift forks which are expensive.

Rob

[rsb502]

if you dont have an air dryer look into one I had a trtxl1070 in my last RW and had the same issue the truck came with a spin on filter for the trans air it did not remove the water so the filters got clogged and crap went into the shift solenoids I rebuilt the shift solenoids and added an air dryer and never had another issue, i replaced my regulator too just in case and set it at 60 as per the shop manual which I found on ebay. pages 9 thru12 are troubleshooting and under slow shift air pressure and clogged system components is the killer also make sure the shift cylinder breather is clear this exhausts the air during shifting and will slow or stop the shift if the air has nowhere to go. te manual is p/n 10-trtxl 107/1010-100.5

[frantzevan]

I am having issue with what u think is pressure. Replaced pressure regulator and both investor valves to no avail. I’m having trouble getting it to shift Into hi from drive. I have to hit it perfect or it won’t go. It used to catch the gear whenever the rpm’s dropped down. I believe it’s pressure related because my shift doesn’t snap like it used to when rotating between different positions. Im fearful to increase pressure and risk bending a shifting fork or worse.. I believe the regulator was set at 70 psi per Mack’s spec. Thank you in advance for any and all help, 

[fjh]

On 7/16/2012 at 2:32 PM, Rob said:

Pretty close to correct. The rear of the top of the transmission has a pair of air shift cylinders integral to the cover. Raise the cab rear if needed and remove the bolts retaining this cover. Lift the cover and stub forks from the truck and rebuild on the bench. A rebuild kit from PAI is about $20.00 and go through the "Selectair" valve on the shift handle also. The regulator pressure should be around 65psi for those transmissions. Don't kick it up or it's hard on shift forks which are expensive.

Rob

You can also pull the cap off the rear of the big range cyl(4 9/16 head bolts) in the truck Check for a broken snap ring! this is a sometimes easy fix BUT Pay ATTENTION to how it comes apart take pictures makes easier for reassembly !

[frantzevan]

I rebuilt the the shifter knob in the cab and I seem to be having the same issue. Air is leaking out of the exhaust line when in hi range 

[frantzevan]

Thank you for the help and info… it’s much appreciated!

[Onyx610]

Hang tight, some of these guys that know will come to help. I won’t be any help to you as I don’t know this trans. 

[doubleclutchinweasel]

Jo-Jo, where are you?  Macktech?  LOL!

Edited October 11, 2022 by doubleclutchinweasel

[Joey Mack]

Im not real smart on 1070's. I believe that's what he has.  But I would look at a split oring in a shift cyl. May be time rebuild the shift cyl's.. new air filter, and confirm air pressure setting..  Simple stuff first..  jojo