Figured this might be the right section to post this question.
Looking at a 69 with CR 4-speed. It has an open 3.0 rear. I have no first hand experience with the difference between CR and WR transmissions.
From what I am reading online, most say a CR needs to be pair with a 3.5 or higher end. It will be too sluggish in 1st otherwise.
“They” say a 3.0 rear should have a WR transmission.
Anyone have any driving experience with both types? Thanks!
Only experience I have with like ratios is my T5-Z. Not the best first gear ratio. I know Ford/Mercury built cars that way. I parted one out about 20 years ago. I would recommend changing the rear gears to 3.25 or 3.50 with a traction lock unit.
I had a '67 GT with a stroked 427. It was 455 cubic inches. I had the 3.00 rear axle with a wide ratio 4 speed. It was awesome. I have also had a Cougar with the close ratio box and 3.00 behind a 302. It was OK but was better when I switched to the WR transmission.
Bottom line I think the close ratio trans will be easy to sell, Boss - 2 guys like them. You might even find someone willing to trade even.
WR has a lower 1st gear, pairs best with rears 3.25 & numerically lower (eg. 3.00, 2.79, etc). If you use gears like 3.50 or 3.73 w/a WR box, 1st gear becomes very short, and more unusable the numerically higher you go.
The CR box has a taller 1st gear, to better pair with those numerically higher gear ratios.
What engine? All 4-speeds used behind 428s were close-ratio. They had enough torque that a low first gear was unnecessary. Likewise, a 390 car should work reasonably well with a C-R and 3.00:1s. Even a 351 won’t be a total dog with that combination, but either a W-R transmission or low ratio rear gears would be closer to optimum.
Engine is a 351-4v. Yes, what you all are saying confirms what I’ve read. The CR with a 3.0 would have been fine behind a big engine. I don’t plan to do any racing but what some jump from the red lights.
As far as changing things up… would it be cheaper to change the rear or get a WR 4-speed? Also, which is easier for a novice?!
Seems like the rear would be easier, plus it let’s me keep the CR. One aspect of this particular car is the rarity in the eng/trans line of the Marti report.
You’ve laid out the pros and cons pretty well. The only other thing I can think of is that a W-R will improve snap off the line without raising engine RPM on the highway the way gears will.
Back when I was running a toploader behind the 351 4V in my '69, I modified it with a 2.87:1 first gear. (Stock W-R is 2.78:1.) I liked that a lot.
Good point on the RPMs at highway speed if I change the gears. Car would be a daily driver but not see much highway time. I’m not concerned about MPG naturally in a car this age. Tough call on this is that is it not local so I can’t test drive it to feel the CR myself. Thanks for the input so far!!
I currently have a wide ratio with a 3.70 gear in mine (255/60/15 tires). It feels like a really high gear off the line compared to my '08 Mustang, which has a 3.38 first gear along with a 3.73 differential gear. First gear in a wide ratio isn’t exactly a low gear, so unless you have an engine with a LOT of torque the wide ratio will be easier to drive. If the CR is original to the car then I’d keep it even if you decide to switch transmissions. I’ve had 2.79, 3.50, 3.70 and 4.56 gears in my car. I feel like the 3.70 is a pretty good compromise gear. If you do a lot of 70+ mph driving then you’d probably like the 3.50 better (assuming you stick with a Top Loader). I’d definitely put a Traction-Lok or something similar (limited slip) in it. It makes a big difference on how much power you can put to the ground. If you’re looking for the easier swap, the differential gear is definitely it. You can just pull the axles, remove the carrier and swap it out with a new one. I’d just get a complete one and not worry about swapping gear sets unless you know someone that has experience swapping the gears (it’s a pretty picky process). If you decide to change transmissions, I’d seriously look at converting to an overdrive transmission. I had an '87 Mustang GT with a 2.73 differential gear, and the 2.95 first gear in the (T5) transmission made it tolerable. It was definitely a lot better when I switched to 3.73’s, though.
So, I am running a 351W with a CR TL 4 spd and 2.75 rear gears. It does ok off the line, but it really needs taller gearing. How do I modify 1st gear to compensate and keep,my highway rear gears? What parts will I need to change out in the transmission. I’m not afraid of going back into the trans as I have already rebuilt it.
How do you like the CR 4-speed over WR? Assuming you have driven a WR which seem very common…
I got the parts to change mine from the late Tom Watts, of Tom’s Differentials. My main goal was replacing the input shaft with something stronger than stock. Not only were Tom’s stronger, they were also a modular design, meaning first gear was replaceable, unlike stock where the input shaft and first gear are a single piece. His design allowed the first gear ratio to be altered with the change of a single gear, rather than requiring complete input shaft assembly replacement for each ratio. He offered several ratios that were not available from the factory. 2.87:1 was his recommendation for my application, and it proved to be a good choice. (Somewhat interestingly, its the same first gear ratio currently offered in the Tremec TKO 600.)
Unfortunately, Tom has since passed away, and while a website is still up for the business, I could find no reference to toploader replacement parts. You could always call or e-mail them, there’s a possibility they still have some on a shelf somewhere. Alternatively, I see that Dan Williams Toploaders is offering modular input shafts now. They mention that they are available for both WR and CR transmissions, and suggest that the different ratios are interchangeable. But I couldn’t find any information about what specific ones are offered. I also don’t know if these are the same ones Tom used to offer, or a different design. Again, a phone call is probably in order if its something of interest to you. I’m sorry I can’t simply direct you to a webpage with all the answers, but I hope this helps a little.