The History of Diamond Reo Trucks – Part III

Editor’s Note: Welcome to Part III of the continuing series, The History of Diamond Reo Trucks, by M.E. Follsom. Click here for Part I and Part II. If you have photos of Reo, Diamond-T, or Diamond Reo trucks in any age, shape, or condition please feel free to share them for possible inclusion in future articles. Email to

Diamond Reo: The World’s Toughest Truck

By: M.E. Folsom


C.A Tilt and the Diamond T Brand

(Part Two of Two)

On March 28th 1958 the ownership of Diamond T passed to the corporate truck manufacturing giant White Motors of Cleveland Ohio. The huge truck builder began its run of acquiring smaller truck manufactures in 1951 when it purchased The Sterling Truck line. That same year the industry titan would complete an exclusive sales and service agreement for Freightliner Trucks. This agreement in effect gave White a west coast truck line to compete against with the likes of Kenworth and Peterbilt without an additional factory and employees to oversee. The next move came in 1953 when White would acquire Autocar Trucks and by 1957 purchase Reo Trucks. (That story arrives in a couple of months so hold on.) The circumstances that led up to the sale of the prestigious Diamond T truck line to White are somewhat convoluted. Ned Tilt, brother of founder C.A. Tilt, was by now the President and General Manager and had started making arrangements for the sale to take place after C.A. Tilt had died on September 19th, 1956. It was believed at the time of his death that the senior Tilt sibling were looking at White for a possible buyout. It was becoming harder and harder to keep a smaller truck manufacturing entity profitable without the injection of government contracts to supply trucks to the military and other governmental agencies. Although the years of 1955 and 1956 saw a substantial increase in sales for Diamond-T trucks overall, the military portion of this picture was carrying the company. The Tilts must have “clearly saw the writing on the wall” so to speak. How long can a company supply trucks to the government? It would clearly be easier for a smaller builder of trucks to remain a viable prospect with the deep pockets of a huge parent. The younger Tilt may also felt the need not to carry on and selling out would offer a financially secure future for him. In return White would get a well-respected brand with a loyal following and a dedicated dealership network. This would also help fill in the gaps of their own truck product line. The plant for the immediate time would stay operating at its present locale of 4509 W. 26th Street in now what was referred to the Cicero area of Chicago.

The Models brought forth by White to form their Diamond-T line were the proven performers catering to the construction, refuse and material distribution fields along with the short and long distance hauling arena. These models included the long haul Model 921FR and 923. The former 921FR could come equipped with a Spicer 5 speed or 12 speed synchro-meshed transmissions with a 2 plate clutch. The very unique feature to this line was the Diamond-T Presto-Matic transmission option. This was a button that the driver could activate turning the standard transmission essentially into a semi-automatic. There was a sensing mechanism that could synchronize the action of the clutch to the engine speed for changing gears, just as a driver would do with his clutch pedal. This semi-automatic option enabled the truck’s engine to build to full torque after engagement of the clutch without ever touching the controls or shifting gears. When the engine returned to its idling speeds the clutch was automatically disengaged. The combination of this system allowed a driver to inch along in heavy traffic without ever needing to keep his foot on the clutch and shift. White made sure to not take away any of the model lines noted accouterment trimmings which had always made Diamond-T so attractive. This wise choice enabled the models to continue to sell moderately well. These two models types in differing variations were also were applied to the vocational markets Diamond–T catered to.


Model 923. Photo courtesy of Roger Amato

Conventional laid-out models were not the only types brought forth, certain Diamond-T cab-over-designs came into the White Company’s fold also. These included the following; the Model 931C for the long haul market and the smaller Model 634OG for the short haul market. The Model 931-C had one of the tallest cab-over profiles in the industry. Drivers toted how they had a commanding vision of the road. These cabs were also offered in three different options from the 50 in. two seater day runner to a full skirted 80 in. ”bustle back” sleeper. Rear single and tandem axle Diamond T’s long haul cab-overs were common place in the mid-west during the late 1950’s and early 1960’s The considerably smaller Model 634C 4×2 day tractor featured a one-piece lightweight fully tilting fiberglass cab for full engine access. The short wheelbase 634C was ideal for the cramped urban delivery markets.

In 1960 the longtime operating Diamond-T factory in Chicago would be closed down and all manufacturing of the trucks transferred to the Reo Truck plant in Lansing Michigan. This manufacturing entity was now dubbed the Lansing Division of White Motors. The smaller number of trucks being built in an off-shoot location did not make financial sense. The Reo factory had plenty room to carry the increase in production without a significant escalation in labor costs. Like the other truck lines acquired by White, the corporate giant would trim down to models it saw fit to continue to make and market. The corporate parent would also start introducing models of similar looks by different divisional brands.

The last true Diamond T rolled off the Lansing Michigan plants assembly line in late 1966, the beginning of 1967 saw Diamond T still being advertised. All in all, through the years as either an independent enterprise or under corporate ownership Diamond T would produce approximately over 250,000 trucks.  No longer able to pursue its own product line development Diamond T had to fit into White’s long range plans. Increasing this meant the sharing of brand components from its other corporate siblings like the R- style cabs from the REO of construction trucks or the D style driver’s cabs from the Autocar line for the long haulers. Many of the Autocar line components would become the main basis for the Diamond-T 1000 line (Westerner) introduced in 1966. The 1000 line included the use of a new lite-weight composite single piece 90 degree tilting hood and fender assembly.  “Royalex” as dubbed by its manufacturer U.S. Rubber (later renamed Uniroyal) was a revolutionary new material found to be ideal in this application. While not as light as fiberglass and other composites it was still an attractive choice because of its hardened vinyl shell and softer ABS plastic interior that offered a higher degree of toughness for many trucking applications. Other common shared models were the construction and refuse industries models marketed as the Diamond-T 4300 and 5300 series models; these were virtual copies of the Reo E-300 series models. White also marketed its own 2000 series models which were derived from all these same above componentry. The only distinguishing feature of the three makes of this model series was a different radiator and grill assembly along with the brand’s emblems. Not only chassis componentry was shared but also power plants as well. The famous and very reliable Reo Gold Comet 6 cylinder gasoline engine was equipped in many Diamond-T trucks. Gasoline engines were still very practical option for truck owners for short run operating and where diesel was not available.


Cross pollination of the brands of White Motor Truck Corporation.

By the mid-1960’s with Diamond T, Reo and some of White’s own line being built in the former Reo plant in Lansing Michigan all three makes began to take on a similar looks due to component sharing. All three marquees utilized Reo’s R-cab and a modified Diamond-T’s 3-piece steel hood.  The dual headlight heavy gauge steel fenders were of a new design introduced in the early 1960’s.  Engine options were the famous gas powered Reo Gold Comet re-branded the DT6-170, or diesels offered by Cummins and Detroit Diesel in the 170 to 210 hp range.  White would also offer in their model a Cummins diesel converted to gasoline dubbed in White’s sales literature as “The Giesel”, this was not very successful. The only difference in appearance for these three truck makes was the radiator grill treatments and the brand moniker on the front top of the grill and engine cowlings. All three model makes were strongly marketed to the vocational fields. Many were outfitted with dump, concrete mixers or refuse bodies.

With two virtually identical truck lines being produced and the corporate parent sharing in some cases the same components for its own line; this cross pollination would result in a brand blurring costly duplication of makes. White Motors strategic plans could not have possibly included this expensive repetition which would result in product identity confusion. In May of 1967 White announced the formation of the Diamond-Reo Division. By combining both makes as one brand executives of the company believed that overall overhead costs could be brought in-line along with an increase in overall sales. C.A. Tilt’s omnipresent “T” was now gone from his beloved diamond emblem only to share space with another truck maker initials with that of “REO”.

    Next month Ransom E. Olds gets his start, until then keep trucking on.        

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9 Responses to The History of Diamond Reo Trucks – Part III

  1. Roger Amato says:

    Nice job again Matt. Glad that you nailed down the Model of the Irving Jensen dump truck. Diamond Ts were their brand of choice for many years.

  2. Ed Martin says:

    In 1969 at the age of 19, I took a liking to and became a life time fan of a DR model C-11464DB and have owned a 1971 for over 25 yrs. It’s the conventional cab with set back front axle, big square long, high, Royalex one piece titling hood with the bold DIAMOND REO letters spelled out on each side. Anything written about DR always caught my eye. But if I didn’t spot a good chunk of information pertaining to my favorite model, I seldom made it very far through the content. After stumbling across this article on the internet, it would most likely meet the same fate. However somehow through the author’s well worded and interesting introduction describing his childhood fondness towards DR, the 3 fact filled segments became “must reads” to me and saved for future reference. Inclusion of a few more pictures or illustrations for each model or feature described would have been helpful to me personally. This is only a comment, not a complaint. My thanks to the author for taking the time to compile the information!

  3. gil says:

    FRANCE bonjour je recherche a savoir le mois jour annees pour mon diamond t 969a ww2 …………numero de chassis 4157 ………….plus le numero sur le capot USA 00…. merci pour votre aide gil

  4. Jess kouba says:

    I have a diamond t model 921 R Cummings twin screw with 5th wheel plate believe 1958 if so that was last year or diamond t name 921r0258 chassis no

  5. Kevin heath says:

    My grandpa had a Diamond Rio in the 60s East Coast Hauled produce all over coolest truckI wish I knew what style it was and what model with a single sleeper in the back semi blow air horn drove truck his whole Independent

  6. DSQUI PONTES says:

    Há um lindo Diamond num museu aqui perto, é um T36, ano 1958. Foram comprados 3 desses caminhões pela prefeitura da cidade de São Paulo. Tenho fotos dele, se precisar.
    Um grande abraço a todos, sou pesquisador de caminhões no Brasil!

  7. Cory Helgevold says:

    How would I go about figuring out the age of a diamond Rio emblem. Part number?

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