Transmissio swap from T2090 to T2070

[Vladislav]

Hi all,

Finally got myself into an entertainment I was going (and avoiding) for a while. Found some troubles and hope finding useful tips. So the help is appreciated.

The truck is 1988 R688ST E6-350 4V Econodyne with T2090 9speed and 5.02 Mack rears. It's for a hobby and no trailer in distant plans.

The reason to go from one tranny to the other is 1st the original one is worn bad, 2nd I could locate a good 7 speed locally, 3rd 7 speed provides higher top hole of 0.60 instead of 0.71 with 9 speed. Also jumping wider steps I hope to drive easier in the city traffic I use to get in all over my place. Not sure all that will be perfect but I'm not prohibited from putting 9 speed back on in the future since total chassis rebuild is on the list. Will need a rebuild and faster rears in that case.

To the moment I took off the original gearbox from the engine and got it on the ground. Had to remove left side fuel tank, big air tank, cab floor and a shift lever. Jacked up the engine a little to get the rear mounting brackets elevated from the pads to be able to remove the tranny. Placed wooden blocks below the engine flywheel housing and than started working with the tranny using the jack and blocks.A trouble was found to get it rearwards enough to clear up the spigot off the clutch bearing since the rear end of the transmission took against the rear cab support bracket. So finally I had to lower the rear end and move it slightly leaning against the crank shaft line what I disliked to do. The unit to go in is even longer having larger compound housing desingned for multi-speed PTO (which I have no need in) so seems the things will be more cantenckerous for re-installation. Current idea is to remove the mounting brackets from the transmission housing and try to put it back slightly biased to the fllor at the rear. But maybe some other options exist?  Also there's a question which might be found as a dumb one. I took the unit off keeping the clutch assembly on the flywheel, the way I always do on cars. But it looked like I also could remove the pressure plate mounting screws through the lower opening and get the tranny together with the clutch. Which way is correct? And what is more important, which one to put it back?

The next issue is I don't have an air schematic for T2070. The pipe connections I have on the unit are different than T2090 has. And they are not complete. Additional trouble is the shift knob on the 7 speed is ruined and I'd like to keep the 9 speed up and down flipper. But it has 2 lines only and the 7 speed one has them 3 or 4. Have no idea of how to make it working the 1st insted of the 2nd and if it's possible at all. As a retreat option I have a shifting knob off T2080B with a revolver style flipper, the same kind as used on TRTXL1070 12 speed. Might work the deal out using that part if knowing how to appange the lines.

Some pics attached below. Thanks in advance for advices and any thoughts on the matter.

Vlad

Edited May 17, 2018 by Vladislav

[Vladislav]

The air lines on T2070 look this way. As you can see some of the connections have no attachments and I don't have knowledge of what to attach to.

[1965]

Only thing I can comment on is; it’s the easiest way to put clutch in by putting it all on transmission front shaft & putting it in & taking it out; let the jack handle the weight!

[Vladislav]

56 minutes ago, 1965 said:

Only thing I can comment on is; it’s the easiest way to put clutch in by putting it all on transmission front shaft & putting it in & taking it out; let the jack handle the weight!

Thanks, just didn't know it's possible that way. Seems also preventing from getting bent anything in clutch while tranny hangs on its input shaft.

[1965]

10 minutes ago, Vladislav said:

Thanks, just didn't know it's possible that way. Seems also preventing from getting bent anything in clutch while tranny hangs on its input shaft.

Done a few that way; makes it very easy all you have to do is get it in pilot bearing. So much easier. Which I know you know to start each pressure plate bolt & rotate engine a couple of times to make sure it all is aligned right & all before tightening.

Edited May 11, 2018 by 1965

[carlotpilot]

2 minutes ago, 1965 said:

Done a few that way; makes it very easy all you have to do is get it in pilot bearing. So much easier.

what do you do about bolting the clutch to the flywheel with the trans .in your face?

[1965]

5 minutes ago, carlotpilot said:

what do you do about bolting the clutch to the flywheel with the trans .in your face?

You stick them in through throw out bearing cover & rotate engine.

[Vladislav]

42 minutes ago, 1965 said:

You stick them in through throw out bearing cover & rotate engine.

What also surprized me is the pulling type of the pressure plate. All cars I dealt with and even my Mack of 1945 had plates a bearing presses on toward the flywheel. You probably can't do your trick with that style so I just kept it out of mind.

[1965]

I knock the wood blocks out they have on the throw out bearing, put it on shaft & hook the the fork. Slide in and install bolts rotating engine couple of times. If you ever do 1 you want do it any other way. Some applications want let you do it that way.

[BC Mack]

Vlad

pics of installing clutch with 18 speed, another trick is to make two guide studs for top as it helps with alignment

BC Mack

[Vladislav]

Ok, looks like it needs twice less travel of a tranny backwards. I had to move it for nearly  15 cm /6 inch to get the pinion out. On the other hand the side mounting brackets were ready to pass the chassis supports about the same time. I will be Ok if put the unit back with no brackets but seems like the same long amount of travel is required for the remove.

There's a point that R-model brackets (twin rubber pads) are wider (longer along a frame rail) than ones on MH or Superliner. So that issue wouldn't show up working on those models.

Thanks the great for guiding me up.

[BC Mack]

Vlad

my other secret is to make a 4 wheel trolley and roll the trans back on it until it bumps into a crossmember, then lift it with a small engine crane, remove the blocking, slide it back some more... easy with a cabover, even easier with a forklift... but it was better to drop it than lift it out, less stuff to move out of the way, you just have to lift the engine enough to have the rear mounts clear then block the trans on the trolley...

my 2 cents, worked for me given the environment I had to work in... didn't need to fully remove the trans, just had a disk stuck to the centre plate..

I also removed my bus engine by blocking up the engine and towing the bus forward..!!! there's always another way to do stuff...

BC Mack

[Vladislav]

20 hours ago, BC Mack said:

Vlad

my other secret is to make a 4 wheel trolley and roll the trans back on it until it bumps into a crossmember, then lift it with a small engine crane, remove the blocking, slide it back some more... easy with a cabover, even easier with a forklift... but it was better to drop it than lift it out, less stuff to move out of the way, you just have to lift the engine enough to have the rear mounts clear then block the trans on the trolley...

my 2 cents, worked for me given the environment I had to work in... didn't need to fully remove the trans, just had a disk stuck to the centre plate..

I also removed my bus engine by blocking up the engine and towing the bus forward..!!! there's always another way to do stuff...

BC Mack

Sean,

Unfortunately I had no trolley handy this time. Would help much. But a cabover is almost another story. I'd just go with a overhead hoist I use to equip every shop I build (the score is 5 to the moment). Having a conventional I got to an idea I'd even remove the cab if the truck has no sleeper. My original plan was to get the engine out together with the tranny but I found no good spots to hook it up. Had nothing of lust to turn head bolts for attachments as Mack prescribes.

Hmm.. Towing the bus forward.. My hat's off to you about that, no doubt. And after a bit of scratching my head it looks to me I also could block Mack engine  and move the truck backwards with its front crossmember and bumper removed. Ok, always something for a next time

Edited May 13, 2018 by Vladislav

[Vladislav]

Roamed around two transmissions today thinking of a mistery of air switch connections and the need of shortening the prop shaft. And after reading  T2090/T2090 repair manual (fortunately I've got it but to my stupidity haven't bought one of T2060/T2070/T2080) a feeling appeared that it's possible to re-install the compaund housing off the 9-speed to the main body of T2070. Making some math it turns out that you get a set of ratios T2080 8-speed unit has keeping sinchronized hi-lo shift with the 9-speed rear end.

Not 100% sure since some Mack-designed "surprizes" might be found such as modified splines on the front main shaft where the main compound gear attaches or different shift forks on the main top cover I'm going to re-install too keeping air shift unit but seems it worth making a try. Going to wash away some grease off the body (transmission's, not mine) and turn wrenches a bit tomorrow. Will share the results.

[fullfuel01]

did you think about the ratio change? T2090 is .71 Od and T2070 is .77 od.. with the 5.02 rears it will be slow

[880joe]

Isn't the t2070 a .60 overdrive like the 2050 2060 and 2080

[j hancock]

T2050  .60

T2060  .60

T2070  .60

T2080  .60

T2090  .71

T2100  .77

T2130  .71

T2180  .71

[Vladislav]

On 5/16/2018 at 5:01 AM, fullfuel01 said:

did you think about the ratio change? T2090 is .71 Od and T2070 is .77 od.. with the 5.02 rears it will be slow

T2070 is 0.60. And that was one of the points. I have original carriers of 5.02 (3 sets at all from 3 ex-SGT R's) and going to go with them in the future if 0.60 tranny will work good. Or I'll put a set of 4.17 I grabbed ocassionally if back to original T2090 with its 0.71.

[Vladislav]

Update on the story.

Investigated the inside of T2070 (longer) compound housing. Looked like the main spline shaft of the main box is longer of its extension which comes into the compound housing. So no easy compound box replace as I was going to provide. I haven't checked it completely since I needed to remove the compound housing off the main one to. Should make a new gasket if do that and also re-set countershafts bearings pre-load as long as the new gasket puts the housing into a "new" position. Hadn't time for all that, maybe will make more rsearch in the future.

Too probably a main spline shaft off T2090 (short compound housing) could be installed into T2070 with all 7-speed gears and slide clutches hanged on it. If so a short compound housing will fit on no problem.

From observation of my original T2090 main box inside it could be seen the slide clutches had teeth edges worn out to about semi-spherical shape. That explanes my difficulties putting it in gear during every shift. You should be extra accurate and usually put a gear in on 3rd attempt anyway.

Being not able to fit the short compound box onto the main one I shortened the prop shaft. Got it from a shop today. Haven't figured out that complicated T2070 air shematic. From tranny description follows that you should put the compaund box in neutral when operate compaund-mounted multy-speed PTO. You take the power from the back box so the main one is in gear. And if you like your truck being stationary during the operation the compaund should be shifted in N. But the shift cylinder has two lines only. This means there should be some special switch (and air lines arrangement) the compound box to neutralize.

Having no info on such pipe arrangement I just replaces the main box top cover from T2090 onto T2070 together with that "clever" air distributing device. That allowed me to keep two-line flipper on the shift lever and it also looked like I'll be able to pre-select with my final setup. The device tracks down the shift rails position not allowing air to go to the compound cylinder until the main box is in N. Original T2070 (and T2060 and T2080) top cover is similar of its shape with T2090 but doesn't have that neutral-checking unit. The top came with no issues, I checked the shift forks - they're same of the sizes and the part numbers either.

After all those leaps and bounds we put the tranny under the truck and lifted it up with the clutch on the shaft as was recommended above. And with no side mounting brackets. The unit itself went on and set wery smooth. But later we had difficult times installing the brackets and turning the pressure plate bolts. On the other hand I'm not sure I'll be able at all to fit that longer gearbox having the clutch on the flywheel. So currently I'm for the together-with-the-clutch install. I say "currently" because I haven't started the engine yet so not 100% sure the pressure plate fit back on completey perfect. No sharp corners during its installation on the other hand, so hope for the good.

[Vladislav]

Was offhome for the weekend so finished the job on Wednesday only. Shortened the prop shaft and put it in place. Spent a lot of time with universal joints stuck in the forks. Didn't want to buy new ones at the moment (found in stock Chinese made only) so had to provide cleaning/greasing.

Took the truck for a ride. Yesterday for half an hour and than today for nearly twice more. Can't say I'm satisfied. Steps between the shifts feel long and the top gear is too fast. Telling more correctly it's not too fast. But you just need a slower one to cruise the speed you like. My actual turn out is I shift in direct on high range at 40-45 km/h (30mph) and drive it very well up to 80 (50mph). But if you put it into the overgear the truck runs relatively good after 100 (60mph). Actually you don't want to accelerate even at that speed because the revs are too low. And after getting faster than 110 (70mph) you are really a king of the road. So covering a "hole" from 80 to 100 (50 to 60mph) is done with direct gear. You can do it but the revs are high and you don't like to cruise a road this way. The rest is good. The gears shift in quite good relating to my old tranny and big steps at lower speeds don't bother.

It seems to me the matter of the issue is not concerned the range of T2070 the most but its combyning with 5.02 rears. If I have them a bit slower (or faster?) I'd be Ok down an avarage highway. Of the ideas for improvement I think a splitter gearbox would help. T2130 13 speed or T2180 have intermediate steps between the main shifts made by splitter. But they both are made basically as T2090 9-speed with additional lowering splits. If you combine the rear box of T2130 with a main one of T2050/2060/2070/2080 you would get what I mean. But I don't have a track on T2130 or 2180 and even shure no one could be found in the whole country. Sure possible to import but seems costy for just an experiment.

Another option which is more realistic is getting back to original T2090 but changing the rears to 4.64. I have them in my cabover. The latter needs attention to its rears so the diffs could be "lended". But the 9-speed content is worn really bad. A good point I have them two similar boxes off two R-models and looks like some parts could be used off T2070 or T2080. Will investigate that deeper after more parting out.

[Lmackattack]

I thought I had hit send on this message a little over a week ago but I must not have as it just popped up here...this is what I had wrote........I hope it works out for you but I dont think you will like it as much as the 9 speed. It will get you down the road faster but those 9 speeds were nice for the highways.

 

 

 

[Vladislav]

18 hours ago, Lmackattack said:

I thought I had hit send on this message a little over a week ago but I must not have as it just popped up here...this is what I had wrote........I hope it works out for you but I dont think you will like it as much as the 9 speed. It will get you down the road faster but those 9 speeds were nice for the highways.

 

 

 

Thank you for the point. I would keep your opinion in my mind if read earlier but now the matter of things is known in fact. And telling that with words which are closer to the truth you know there are some dumb folks who never trust completely until making a try...

[Lmackattack]

Yep my friend some times trial and error is the best way to learn. but good on you for giving it a go.

 

I was never a fan of the T2050-2060-2070-2080 series of transmissions. they were very specific to what mack rears had to be used to get the gearing right and they really had useless low gears on the low side that you sometimes had to use to get a load moving before going back into hi. the old 2 stick 6 speed or 12 speed was a better transmission by far.    a freind of mine had a R model with a 350 and a 9 speed with I think 5.02  mack rears on 11r22.5 tires. it was a over the road truck and I drove it from Chicago to New York a few times hauling U.S. mail.  I thought it was absolutely a great truck to run OTR with.  It would do 65MPH at 1800RPM so when a hill came up on you , the RPMs were right where they needed to be. you just held it to the floor and it would hold the gear most of the time....It maxed out at just under 80mph at 2100RPM.

[Vladislav]

Hmm.. I had 9-speed with 5.02 on 11R24.5 and the truck topped out at nearly 70mph if check with GPS and a bit more by its speedo. I couldn't know the revs since the tacho was disable (found the cable broken so hope to fix) but the truck didn't want to go faster due to the revs limiter what wasn't nice on my mind. I can cruise some parts of highways here doing 120kmh (75mph) but usually you go 90 (55mph) as other trucks do. So in general T2090 was a quite good unit. My feeling was you had to make too many shifts to accelerate an empty truck starting from lights or a crossing but mostly it was a matter of fact that the slide clutches made every shift as a disaster being smoothed out on teeth corners as I could see after opening the top cover. Wouldn't try a fortune with different setup if my stock tranny operates sutable.

As another possible option I got lucky locating a 12-speed with a company of two 4.17's off a R-model parted out. Seems as a good choice about the ratios as long as you can drive 12-speed in a 5-speed manner or split if you like. But my current position is to keep the R closer to its stock configuration. And if with a different model of transmission so at least of the same T200 series. As for the 12-speed I'd like to keep it for another project

[Lmackattack]

I just checked the road speed calculator and with 5.02 rears with 44" tall rubber and a final transmission over drive of .71 that will put you at 77MPH at 2100 RPM or 66MPH at 1800RPM. if you have a low RPM motor I would have the pump re calibrated up to 2100RPM spec. I disliked the low RPM mack motors as they never really came alive like the 2100RPM engines do.

I would go as far as saying I like the 9 speed better for pure over the road use other than the 12 speed.   but of you do any off road dirt work the 12 speed is much better as you have all the low gears and 5 reverse gears.

I always drove a 12 speed like a 5 speed when empty. some times I would start out in low 2 and shift up to 5th and then split 5th into over drive.

 

 

Trent