So if I get a hold of Canadian rings and pinions

[Don1357]

Which I see going for the low-low price of $600 per set (sadly American, not Canadian, plus shipping), that, plus seals, bearings, gear oil, (and somebody that actually knows how to set backlash/preload adjustment) should let me regear one of these green puppies? That assumes that the Canadian ring/pinion is compatible with the American carrier; is that so?

A bit of background; I'm looking for a forever truck. I'm of such an age that I'm not as much in a hurry, but 45mph can suck the fun out of life from time to time. I could live a happy life around 55MPH or so, specially without the rig shaking like a wet dog trying to dry itself.

Based on reading around this is what I'm pondering:

- One of the biggest obstacles to speed (the 55mph or so I want to cruise at) is not the differentials, but the engine itself. It being a low RPM, unbalanced engine; even if made to spin faster, the fact it is unbalanced would put a lot of stress in it. Not to mention the noise and the shake rattle and roll. I would imagine that a rebuilt, rebalanced engine, could sping quite happy at a slihgtly higher RPM.
- A modicum of bigger tires could pick up 3~5MPH without spinning the engine faster, but I would like to stay close to the stock look.
- And of course a well maintained drive and steering trains would go a long way towards keeping everyhing from shaking around.

Basically, while I am primarily asking about regearing the differentials, I'm taking a long view as to what it would take to make one of these more enjoyable to drive. If I pick one I would be on the lookout for a stock engine to rebuilt to better specs.

 

[eaw46]

You might have an issue right now with the Tariff on importing parts from Canada it could drive the price up a lot.

 

[JimC2]

My 37 with big block Chevy, SM465 transmission, and 5.83 differentials will do more than 111 mph.
How fast do you want to go?

 

[Don1357]

My 37 with big block Chevy, SM465 transmission, and 5.83 differentials will do more than 111 mph.
How fast do you want to go?

About half that

I would like to stay pretty close to stock. To me (the ignorant newbie) it seems the the real issue is not the differentials, but an unbalanced low RPM engine that is prone to get mighty pissed if pushed at high RPM for long.

So phase one would be to go 4.88:1. That lets me gain a bit of speed from the current power plant spinning at the same RPM without hurting anything. According to my bad math skills; if the rig is doing 45mph on a 5.38:1 differential, that would be (at the same RPM) 49.59mph on a 4.88:1 differential. Adding an inch of radius to the tire size would add another 3.5MPH or so. Obviously it is not going to be as peppy as when geared lower.

Phase two would be to source and rebuild an engine for it, either a stock engine or the slightly larger Canalandian version with a few more ponies. Heck a properly built stock engine that is balanced should be able to push quite a few extra ponies and spin at a higher RPM safely.

I take it you are not running stock differentials? I don't think they were built to spin that fast and would experience a lot of wear.

 

[John Mc]

Not sure if that was just a typo, or if you have the wrong number for the stock differential, but stock is 5.83 (not 5.38 )

I'm told that the Canadian 251 engine will hold up to high RPMs a bit better than the 230 that was in the American version. (Take that with a grin of salt: I'm far from an expert on these engines.)

 

[Don1357]

Not sure if that was just a typo, or if you have the wrong number for the stock differential, but stock is 5.83 (not 5.3

Got the wrong number filed on my brain :-\. Which is good, because from 5.88 to 4.88, the speed gain for the same RPM would be a bit over 8 1/2 mph. If my math is not failing me, a 5.88:1 geared rig traveling at 45mph, would travel at 53.68mph. From there if a vehicle traveling at 53.68mph on 35" wheels had 37" wheels, for the same RPM it would travel at 56.93mph.

Obviously we are not inventing a free energy machine here so I would think the engine would struggle a bit to maintain torque... But struggling to maintain torque is less damaging than spinning too fast and choking on a con rod. I figure that struggle would eventually be fixed with a fresh stock engine that is built better, or with a Canadian engine that has more ponies to dedicate to the cause.

 

[JimC2]

" if the rig is doing 45mph on a 5.38:1 differential"
"because from 5.88 to 4.88"

Are you sure you don't mean 5.83?

"I take it you are not running stock differentials? I don't think they were built to spin that fast and would experience a lot of wear".

Yes, I am running stock 5.83 ring and pinion. And no, they are not built to spin that fast. The engine was turning over 6500 rpm. It was one of those once and done things - my 37 is scary at more than 70 mph.

 

[Don1357]

" if the rig is doing 45mph on a 5.38:1 differential"
"because from 5.88 to 4.88"

Are you sure you don't mean 5.83?

Yeah... As I said I'm a newbie at these, so the numbers are not ingrained in my mind just yet. But as I mentioned to the other poster that actually makes the math work on my favor.

Another question I have is how much performance can be had from the stock engine just by building it better? Just having it balanced should gain quite a few RPMs and more power.

 

[JimC2]

Not really.
Why would balancing your engine give you more rpm?
Wouldn't the governor still limit you to a maximum of 3200 (depending upon governor setting) ?

I put a 318 in my 37 back in the late 1960s and ran it for a couple of years. It was a lot perkier than the 230, but still pretty anemic. Mileage increased from 11 to 13 mpg though. That said, the 230 will have plenty of torque when in low range.
Around 1970 I pulled the 318 and installed a big block Chevy with 375 hp and a lot more rpm capability. Mileage went back to 11 mpg, but highway speed improved. I've been happy with the BB for over fifty years.

I'm refurbishing my XM708 now and am seriously considering boring and stroking a 360 Magnum to 410 cubic inches and doing a reversible installation of it in place of the 230. I know from experience that I would be happy with the performance and with the stock 5.83 differentials would expect about 11 mpg average. Maybe a bit more because I've gone to tires that are four inches larger in diameter than stock.

 

[Don1357]

Not really.
Why would balancing your engine give you more rpm?
Wouldn't the governor still limit you to a maximum of 3200 (depending upon governor setting) ?

I put a 318 in my 37 back in the late 1960s and ran it for a couple of years. It was a lot perkier than the 230, but still pretty anemic. Mileage increased from 11 to 13 mpg though. That said, the 230 will have plenty of torque when in low range.
Around 1970 I pulled the 318 and installed a big block Chevy with 375 hp and a lot more rpm capability. Mileage went back to 11 mpg, but highway speed improved. I've been happy with the BB for over fifty years.

I'm refurbishing my XM708 now and am seriously considering boring and stroking a 360 Magnum to 410 cubic inches and doing a reversible installation of it in place of the 230. I know from experience that I would be happy with the performance and with the stock 5.83 differentials would expect about 11 mpg average. Maybe a bit more because I've gone to tires that are four inches larger in diameter than stock.

The 230 is an industrial motor built for low RPM, high torque applications. Because of the low RPM rage, there was no need to even balance the engine; it was supposed to say bellow what, 2,600rpm? I would imagine that if you attempt to fiddle the governor to allow for a higher RPM, reaching said higher RPM would make the engine feel like an uneven washing machine o the spin cycle. Oh, and likely to break a con rod.

There is a laundry list of benefits from balancing an engine, from increasing HP, less wear, less vibration, longer engine life, better gas mileage, and yes; the ability to push higher RPMs without stressing the engine as much. At 45mph the engine is spinning at 2,400rpm. On a well rebuilt and balanced engine you could probably set the governor to push 2,800rpm which would put you at 55mph.

Another source of performance would be raising the compression ratio, which would give you more horse power, better torque, and be more fuel efficient. Then again it would force you to use premium gas so no gas savings from it being more fuel efficient.

Some may consider this to be putting lipstick on a pig, considering that you are starting with a engine whose stock rating is 95hp. You could easily outperform a stock 4BT engine (rated at 105hp) but you are unlikely to reach the power of the updated 4BTA (rated at 170hp).

 

[JimC2]

"it was supposed to say bellow what, 2,600rpm? "

From memory, stock governor setting for the M37 230 is 3200 rpm timed at 4° BTDC.

These engines were also used in Dodge, Plymouth, some Desotos (218 c.i.), and Chrysler passenger cars. Isn't the M37 power closer to 78 than 95hp? I had one in a 1954 Chrysler Windsor back in the late 50s, early 60s, but it was the 265 c.i. version rated at 119 hp. If running on regular gasoline, I wouldn't take the 230 compression to more than 9.5

 

[John Mc]

Another source of performance would be raising the compression ratio, which would give you more horse power, better torque, and be more fuel efficient. Then again it would force you to use premium gas so no gas savings from it being more fuel efficient.

The stock engine compression is low, per TM 9-8030 it's 6.7:1. If I recall correctly, the engine is rated to run on 80 octane fuel, but I can't find that spec at the moment. You can definitely get some gains without having to go to premium fuel.

Isn't the M37 power closer to 78 than 95hp?

For the 230 engine, the Wikipedia entry for the Dodge M37 shows 78 HP in one place, then in a table further down in the article shows 94 HP max (by which I assume they mean Gross HP without any accessories installed) and 79 Brake HP (HP delivered to the wheels). That 78 HP in the Wikipedia entry has cropped up in other places, but I have never seen it listed in any official technical manual. I'd love to know the source of that number. Has anyone found it in an official publication?

TM 9-8030 (see pg 19) and the newer TM 9-2320-212-20 (pg 1-3) both show 94 Brake HP at 3400 RPM and 57 HP at 1600 RPM


For the 251 engine, the Canadian CDN-VEH-D114 manual (pg 55) shows: Gross HP without accessories as 106 HP @ 3600 RPM
and 95 HP @ 3400 RPM with accessories. (No info on Brake HP is given that I can find.) Compression Ratio is listed as 6.6:1.
When I've asked a few knowledgeable people about the difference in HP between the stock 230 in an M37 and the 251 in an M37 CDN, I usually get fairly vague/uncertain numbers, but most seem to think it's around 10-12 HP.

 

[JimC2]

From memory, compression ratio in 230 is 6.5 and in 251 is 6.6

 

[G744]

The T245 (M37 spec) engine was listed to run on 68 Octane gas per the dashboard data plate.

And, who in Canada is selling 4.88:1 R&P gears?

G744

 

[John Mc]

The T245 (M37 spec) engine was listed to run on 68 Octane gas per the dashboard data plate.

And, who in Canada is selling 4.88:1 R&P gears?

G744

Thanks. I knew it was something low, I just did not remember it being that low. What data plate does that appear on and where is it mounted? I don't have that one on my truck.

 

[John Mc]

From memory, compression ratio in 230 is 6.5 and in 251 is 6.6

6.7 in the 230, per TM 9-8030 and the newer TM 9-2320-212-20