I'd check with the Cat dealer about optimum RPM. Most "real" diesels are oversquare (stroke is larger than bore) and are designed to run at lower RPM, where the torque (due to the leverage of the longer crank throw) is around peak. I don't recall the 3208 being any different from the Cummins 225/250s or the GM 6-71/8V-71s that I drove, and they ran on the Interstates around 1600-1800 RPM. But I had a few customers who got early 3208s, and I recall the drivetrain setups over the replaced the GMs and Cummins were basically the same, which would put the cruising RPM at about the same, too. I may just be full of Bazanga, but I'm pretty sure 2400 RPM is higher than the 3208 needs to run.

There are two options - adding overdrive facilities (Gear Vendor or better, Allison stock parts) to the transmission or having the differential redone with a taller gear ratio. Personally, I favor the former, because shorter diffy gear ratios mean less stress on the diffy gearset.

Bill N Y probably has a much better grasp on what Allison dealers can do to a transmission.

quote:

Originally posted by Rusty:
Most "real" diesels are oversquare (stroke is larger than bore)

Isn't that undersquare?

Yeah, it is. See what you have to look forward to when you reach my age?

Some info I dug up about 3208s old info but it does suggest that 2400 is on the high side.

3208NA 165 HP - 165 HP @ 2600 RPM, 398 ft-lbs TQ @ 1300 RPM
3208NA 175 HP - 175 HP @ 2800 RPM, 405 ft-lbs TQ @ 1400 RPM (425 ft-lbs TQ for California models)
3208NA 185 HP - 185 HP @ 2600 RPM, 452 ft-lbs TQ @ 1400 RPM
3208NA 200 HP (California only) - 200 HP @ 2800 RPM, 490 ft-lbs TQ @ 1400 RPM
3208NA 210 HP (all states except California) - 210 HP @ 2800 RPM, 500 ft-lbs TQ @ 1400 RPM
3208T 210 HP (California only) - 210 HP @ 2600 RPM, 575 ft-lbs TQ @ 1400 RPM
3208T 225 HP (all states except California) - 225 HP @ 2600 RPM, 560 ft-lbs TQ @ 1400 RPM
3208T 250 HP - 250 HP @ 2600 RPM, 610 ft-lbs TQ @ 1400 RPM

Again the optimum place to run for efficiency is the lowest possible RPM but not below the peak torque RPM, For overall highway use and response many design their drivetrains to run about midway between the torque peak and HP peak RPM. This suggests about 2000 RPM would be OK. Abit lower would be even better.

I don't think a Gear Vender option would work in a diesel pusher, the driveshaft is already so short that there may be nothing left. The 4 speed Allison do not have an extra gear inside that can be tapped, so really the only option would be to change the trans or diff to lower the RPM. If the diff is changed for lower cruise RPM speed, that will have a negative effect on acceleration. The best would be to install a 5 or 6 speed trans and that also might involve a change of the diff as well to get the proper balance of acceleration and lower cruise RPM. If you don't do the work yourself, it will be an expensive proposition. I doubt that any fuel savings would pay back the conversion costs over the remaining lifetime of the coach.

HTH

Is 250 hp as high as they went on 3208s in RVs? Some Barths have been advertised with 300 claimed hp 3208s, but who knows? I have seen some higher figures for boats, but maybe pollution enters into things.

How does the 610 ft lb torque of the 250 3208 compare to a 250 hp Cummins 8.3?

The numbers that I posted are from an old list, I think it is pre-1983-4. I have seen many adds for RVs wth 3208 rated at 300HP and some even higher but didn't pay a lot of attention to them. Boat Cat 3208s applications go into the 400s

Don't have any data on the Cummins 8.3 but will check with my brother, he has a fleet of trucks that are mostly powered by the 8.3L and some Cats.

The higher-rated 3208's (3208TA) had both the turbo and aftercooler. The early 3208s (3208NA) were naturally-aspiriated.

The ISC (8.3L) is typically rated 350HP, 1,050 lb.ft. torque at around 1500 RPM. I'd guess the earlier 6C was somewhat lower.

And my guess on the optimal RPM for the 3208 was about right (even a blind hog finds an acorn now 'n' then). 2400 RPM is just much higher than that engine needs to run (isn't yellow line around 2800 RPM and redline around 3200?) Too many years since I looked at gages on tractors....

first thing you need to do is call cat with your engine serial number to find out what engine you have. i do have a 3208 in my rig and it is a 300 hp,this engine is actually a truck engine. the highest a 3208 goes is a 300, all else was a different cat engine.i also have a allison trans,it is a four speed with two lock-ups in the tourqconverter.my rig is 38 ft and runs 60-65 mph at 2300 rpm. this engine was bult to smoke when cold because of the timeing. this info came from one of the guy's at cat that help developed the engine. the engine needs to say around this rpm. if you change the gearing on a 300 hores engine you will change the rpm and this will shorten the engine life. hope this will help!!!!!!!

Gary, post as soon as you have some more info. i have been talking with Ted at TKTsales and i am looking for a good 2000 series trans to replace my AT545. I don't have a Barth, i have a 1999 blue bird bus/motorhome conversion. I have been studying specs and diagrams of the AT545 and the 2000 series and I can tell you a couple of things i learned.
the length of the 2000 is only 0.8" longer than the AT545
Ted told me that he didn't think that the driveline brake off the AT545 would work on the 2000 because the linkage works backward. i think that it will work wtih a couple of new brackets. it looks like they used the same bellcrank and just rotated it 90* and mounted it on top of the 2000 with a couple of re-designed brackets. according to the diagrams i a looking at the part numbers for the parking brake are exactly the same with the exception of those 2 simple brackets that you should be able to buy from blue bird or maybe elsewhere. here is the link to blue bird with diagrams of both ransmissions and parking brakes etc. Hope this helps and looking forward to a progress report. Dave Diamond
http://service.blue-bird.com/Parts/A3FE/A3FE_035_BrakesHydraulic.pdf

quote:

Originally posted by Gary Carter:
Ok, the Allison source is Ted Keating. He has a web site www.tktsales.com. Don't know if I am suppose to list it or not, but Ted gave his ok.

He worked for allison for something like 13 years and now just sells allison parts. He seems to know what fits what. Plus what program I need in the TCM.

The 2000 I got has a brake. On the 542 the handle points to the street side and on the 2000 it points up.

This is not a problem with the spartan chassis a the parking brake is cable operated from an air cylinder. It is actually a spring brake that activates when no air pressure is available. The cable runs along the frame rail and then makes a 180 degree turn back to the 542 transmission where it is attached to a bell crank which pulls the brake on. On the 2000 I need to loop it to the other side of the transmission and operate the brake directly. The cable appears to be plenty long(I hope).

Since I will be using the output yoke from the 542 I may need to use the brake drum from the 542 also.

My progress is slow, but so am I. We were on a cruise for a week and when I got back to Yuma I started to wire the J2 plug.

A word to those looking to buy a transmission, get the wiring harnesses. If you got one out of a Chev all you need to add is the TPS wires (3) to J2 and you could use the J1 harness as well. Plus the TCM which will need to be reprogrammed.

You can use a 1000 from a Chev PU, but you really need one with the brake installed. As I get further into this project will let all know if the 542 brake would fit on a 1000/2000. I have seen 3 transmissions on ebay with the brake assembly.

You will need to change the bell housing to an SAE3, but that turns out to be a bolt on. Used housings are available for in the $100 range.

To remove the torque convertor from the engine you remove a cover from an access hole on the left side of the engine bell housing. Above the access hole is another hole. And here is the big helper. You should get a Cummins Diesel engine barring tool. This goes into the upper hole where it makes contact with the flex plate and with a ratchet you can turn over the engine to aline the bolts in the access hole.

I may be old and slow, but like a turtle I do make it.

The Allison 542 is out and the Allison 2000 is .in and mechanicly hooked up (almost). As previously stated and now proved the 542 flex plate bolted up to the 2000 torque convertor. So it was really just a bolt in. Removed the output yoke which also has the brake attached and swapped it with the 2000. Keep in mind the 2000 I bought had the brake. Simply reinstalled the drive shaft. Appears to be no problem there.

The brake on the 542 was on a bell crank and pulled to the rear. The cable came from the front and made a U turn. On the 2000 I ran the cable under the brake and up to the top. There was plenty of cable to do the reroute.

Last was working on the shift cable. Looks like it is a go here also. According to the book I bought on the 2000 5 speed it uses the same shifter that is in our breakaways. The sequence will now be 1,2 4,5(drive).

After the shifter will come the wiring. More on that later.

I am right behind you Gary. I got my new used transmission 2 weeks ago. disconnected everything and pulled the AT545 out on Sunday 15th. went to put the new one (model 2400) in and discovered that it had the sae2 bellhousing and would not fit. the salesman at the salvage yard in Iowa had assured me twice before i purchased it that it had the sae3 housing that i needed. spent Monday 16th gathering up estimates for labor and material to get the housing changed out. Ted Keatting (tktsales) had a used bellhousing and sold me that and all the gaskets, o-rings, seals, etc. that i needed to make the change. he recommended that i not try to change it out myself and i am glad i took his recommendation. I hauled the 2400 to Mobile, Alabama yesterday morning and they spent an hour and 1/2 changing the bellhousing and then put it on the dynomometer to check their work and run it thru its paces. Main pressure was extremely low. CRAP, a bad transmission? after some discussion they decided to tear it back down and check their work. they found a gasket out of place. put it all back together and on the dyno again. Hooray, it checks out good. the salvage yard has agreed to reimburse me for all my out-of-pocket expense for changing out the bellhousing so i'm not mad. On the way home, i stopped by a diesel truck mechanic shop and they made the 3 parameter changes i needed in my engine computer so it can now talk with my trans computer. I just pulled the engine computer off and took it with me and they made the changes while i waited.

This morning i put the engine computer back on and a friend came over to help me put the 2400 in and bolt it up. like you, i was able to use my flexplate adapter ring from my old converter on the new one. I bought 2 brackets from blue-bird for a total of $24 and it looks like these 2 brackets are going to let me bolt up my old parking brake cable without any further modification. I also bought a new dipstick and tube assembly and coolant hose fittings from blue-bird. i can adapt those fittings to fit my old coolant hoses. the 2400 uses larger hoses so i will keep a close eye on my trans temp and if it looks like bigger hoses are needed i will change them out later.
My wiring harness and computer for the transmission (bought from Ted at TKTsales.com) are due in by UPS tomorrow and i hope to get it wired in and ready to run before the weekend.
the 2400 is just one variation of the 2000 model series. It has a lower low gear and it has the parking pawl like the 1000 series. it is also rated for 26000 gvw instead of 30000, like the 1000. i am almost sure that the reason for the lower gvw rating is the parking pawl.

It's in and working. Shifts so smooth I can hardly feel it. Was really nice going into 5th gear and the engine idling at 55mph. Still have a problem as the trans light stays lite. Ted is sending me the reader to figure out the problems.

When all is complete I recap everything in one report.

quote:

When all is complete I recap everything in one report.

I hope you took plenty of pictures.

If you need me to host them, send them my way.

Bill N.Y.