Allison MT654 VS MT654CR?

[glj]

Sorry if this question is too simple. I have 3 trucks and tractors that use the MT654CR tranny. Looking for a backup spare. GL will soon be auctioning some "MT654" trannys (CR not stated in the ad) and they say that it is specifically for the M934A2. I thought all M939 series 5 tons (i.e., M923, M936, M931, etc.) used the MT654CR. So the natural question is : Are the MT654 and the MT654CR one and the same transmission, or does the implied specific use in the M934A2 mean that there is a difference between the MT654 and the MT654CR?Thanks very much, fellas, and ladies.Gary

 

[Suprman]

They should all be the same. If you want to be sure see what they list the nsn as and cross reference across the m939 series manuals

 

[glj]

Nope. The auction part for the M934A2 van is NSN 1920-71-166-9085, while the NSN for the M939 series (which includes the M934A2 van truck) is 2520-01-117-3010. Odd. Darn. Auctioning lots of new ones, and this is my luck. Whine. I will call Allison to see if they can clarify the difference. But a sincere thanks for your suggestion. Gary.

 

[glj]

Clarify

I should clarify that the M939 series transmission NSN # is 2520-01-117-3010, except for the M934A2 van truck transmission, whose NSN # is 1920-71-166-9085. Wish I was lookin wrong, but this is what it seems to be. Thanks again.

 

[Suprman]

Maybe it's just different mounts in the van.

 

[av8or]

It appears to have so extra lines & valving on the out side from pictures.

 

[glj]

A factory trained Allison tech told me today that there is no difference in an MT 654 and an MT 654CR (closed ratio); but acknowledged there is a difference in the MT 654DR. Auction is almost over and still don't know what to do. GL is so "wrong" in much of the descriptions they publish, but when they make a strong statement that their MT 654's are only for the M934A2 I have to pause.

 

[insas]

I saw those trannies as well and was wondering why they were only for the vans. If the price isn't bad, it may be worth picking up, then you can see what if any difference there is. If they are not at least compatable/swappable, it should at least make a good "rebuild kit...."

 

[glj]

Thanks, all. I just noticed the banner across the top of this page, in reference to auction details. I just frantically tried to delete my posts but am electron challenged and the mechanism wanted me to edit as opposed to delete the post. The principle focus of the post was not an auction or ad, but differences in transmissions. I hope that I remain a member but if I go "poof" you will know why.

 

[CBR Metalworks]

Since there are a lot of the transmissions being auctioned hopefully there won't be a problem, if there was only one it might be an issue.

 

[quickfarms]

It appears to have so extra lines & valving on the out side from pictures.

Could it be set up for the retarder?

 

[glj]

Could it be set up for the retarder?

Listen here, I'm the retarded. lol. I don't know what a retarder is. Are they in the M934A2's and not others? My application would be an M936A1. I've been comparing lots of NSN and P/N's and the M934A2 and M936 each seem to take different MT 654 setups, whereas the M923, M931 and most others of this series have the same numbers.

 

[dependable]

I thought the CR designation was for 'close ratio'. Less difference in ratio between gears. Used in civilian applications like trash trucks, local driving, not a lot of highway speed.

 

[glj]

I thought the CR designation was for 'close ratio'. Less difference in ratio between gears. Used in civilian applications like trash trucks, local driving, not a lot of highway speed.

You are correct; "close ratio." When I was typing I added a "d" inadvertently (i.e., closed). My understanding of the use of the CR transmission is that most of the M939 series were designed first as "off road tactical" machines.

 

[CARMAN]

So to bring this to life...should one who is looking for a replacement in an A2 truck look for a non CR for better drive ability?

 

[simp5782]

They are about the same ratios between the Non CR and CR version.

Remember that the torque converter and front pump in an A2 truck are different from that in an NHC250 truck.

You could try for an MT653 transmission. it is all about the same with a really low 1st gear and every other gear is near the same. Same bellhousing setup as well for bolting to the 8.3. Or try to find an SAE1 bellhousing and hook a HT740 to it as those are pretty abundant and overkill. not to mention cheap. Even new MT654s in the can are known to be bad.

 

[CARMAN]

Is a 740 same length? As in direct swap? Says only a 4 speed.?

 

[simp5782]

Is a 740 same length? As in direct swap? Says only a 4 speed.?

Not a direct swap. Why I mentioned the bellhousing swap. It is a heavier transmission.

Gears doesn't matter as it is a direct final drive, the same as the 654.

 

[CARMAN]

But with the BH will i need driveshaft modification? Looks like it handles more HP too. May be a good idea if I bump the power and move to 16.00 X 20

 

[74M35A2]

Go manual and row some gears! If you get one with a range selector, you can have 4 speeds in reverse. How cool would that be to see a 9-ball shifting gears while going backwards? That alone would pick up chicks all day long.