Differential swap

klr650goldwing wrote:
Sorry for the delay on this report. I picked up the truck and 5er last Saturday. We were running an '04 SD V10 CC SRW LB 3.73 as our tow vehicle pulling a 10,000 lb 5er. The truck did okay here in flatland country, but even on the flat it shifted down often. It seemed like even the slightest rise would bring on a downshift. That concerned me because in less than two years we will retire and head out to see ALL the national parks. Traveling up ANY mountain, I thought, would put tremendous strain on the transmission. So we had the differentials changed to 4.56.

On the drive home the tranny shifted down very seldom. Now, granted the drive home is very flat, but still, the difference is amazing. The truck has significantly more power than it had before. It is much more enjoyable to drive now.

Prior to the change 70 mph produced 2000 rpm. Now 70 mph produces 2450 rpm. Driving the truck without the trailer the increased rpm is not the least bit annoying.

So far, I'm happy with the change.

Delay, heck. We're lucky you came back. Glad to hear you like the change. I wonder if my buddy wouldn't also like the change on his 2000 F-250 V-10? He went from a Dodge-Dakota-sized 5vr to a larger 11K 5vr and after the shock, he has lamented the loss in performance ever since. You wrote some convincing testimony to better performance.

I'm satisfied with my V-10 3:73 Excursion only pulling 8K, and we do use it for winter passenger service on trips to Minneapolis, so I worry that my 13-14mph might suffer with other gears. On the other hand, I can only hold OD during low wind conditions towing on flat roads such as I-94 in ND. I usually try to pull at 60 mph. ND does have a 75 mph speed limit, but non-towing I usually stick to 70 anyway, like Minn.

Please pardon a little deviation here:
I see you have several bikes like I do. Most of my experience in gearing changes has been sprockets. I first had a (purple?) 300(305) Dream that came in a basket and sold the same way. Besides small missing parts, the buyer ended up putting a new crank in it.
Sample:


One other possibly of note to you is a 1981 CB900c 5 spd which has a dual-range sub-transmission that converts it to shaft drive. The "low range" gives it a lot more zip with ten speeds altogether. This vintage "touring" bike is extra heavy with optional bags, trunk, full Vetter fairing, so the low range is handy at times. I made a trailer for it but DW refused to consider it. The early "touring" options were shared with the early GoldWing at the time.
"Naked" sample:


Another is a pair vintage '66-'67 Honda 305 Scramblers. One is complete except missing the original front fender. The other was my first dirt bike and I had two rear tires/wheels (w/sprockets) for it, on-road/off-road. On the road, it was geared so tall, I had to occasionaly shift to 3rd on a hill. But the snappy large dirt wheel/sprocket topped out at 60 mph off-road at somewhere around 9 grand.
Sample:


None of these bikes are currently running. All the insurance and tags kill me. But... ahh the memories.

Just passed :( , on a 2008 Yamaha WR250R, a sort of miniature version of your KL650.

Good luck on all your journeys.

Wes
...

klr650goldwing wrote:
Sorry for the delay on this report. I picked up the truck and 5er last Saturday. We were running an '04 SD V10 CC SRW LB 3.73 as our tow vehicle pulling a 10,000 lb 5er. The truck did okay here in flatland country, but even on the flat it shifted down often. It seemed like even the slightest rise would bring on a downshift. That concerned me because in less than two years we will retire and head out to see ALL the national parks. Traveling up ANY mountain, I thought, would put tremendous strain on the transmission. So we had the differentials changed to 4.56.

On the drive home the tranny shifted down very seldom. Now, granted the drive home is very flat, but still, the difference is amazing. The truck has significantly more power than it had before. It is much more enjoyable to drive now.

Prior to the change 70 mph produced 2000 rpm. Now 70 mph produces 2450 rpm. Driving the truck without the trailer the increased rpm is not the least bit annoying.

So far, I'm happy with the change.

This is exactly what I expected.
Great to hear you are happy with the swap :B

Thanks for the update! The difference is very amazing. It's like the whole combo loses a few thousand pounds!

Now I'm curious to see your mpg with the gear swap!

Sorry for the delay on this report. I picked up the truck and 5er last Saturday. We were running an '04 SD V10 CC SRW LB 3.73 as our tow vehicle pulling a 10,000 lb 5er. The truck did okay here in flatland country, but even on the flat it shifted down often. It seemed like even the slightest rise would bring on a downshift. That concerned me because in less than two years we will retire and head out to see ALL the national parks. Traveling up ANY mountain, I thought, would put tremendous strain on the transmission. So we had the differentials changed to 4.56.

On the drive home the tranny shifted down very seldom. Now, granted the drive home is very flat, but still, the difference is amazing. The truck has significantly more power than it had before. It is much more enjoyable to drive now.

Prior to the change 70 mph produced 2000 rpm. Now 70 mph produces 2450 rpm. Driving the truck without the trailer the increased rpm is not the least bit annoying.

So far, I'm happy with the change.

Sorry guys. The trailer wasn't ready yet, so I didn't pick it up. They now say this next weekend will be the best time to pick it up. So, hang on until next week.

klr650goldwing wrote:
Well, I went ahead and swapped differentials for 4.56 gears. I was also talking with guys on the Ford Super Duty site. I might regret this as some of you have indicated; time will tell.

I think I'll be picking up the truck and trailer this weekend. Will let you know how it performs on the way home.

Where is our trip report? ;)

wes wrote:
dodge guy,

Thanks for the voice of experience. With my lighter TT (8k), I only drop to 2nd once in a great while around ND with my Excursion. But it might be pretty common to hit 2nd in the SD Black Hills, or mountainous regions. It already seems like 2nd is then a bit too low, even for 3.73's, but there is no intermediate gear between it and 3rd. Since 2nd sometimes already spins the rear tires, 1st is way too low, unless one has 4x4 engaged to spread the traction.

My buddy has an extended cab 2000 F-250 and pulls a 5vr closer to 11K with 3.73's. He shifts to 2nd more often than I, even occasionally on the ND I-94 if bucking a good wind on a hill. He recently likely overheated his tranny, blew a tranny seal, and lost his torque converter in the Black Hills. I will say that he probably had a hard time maintaining over 35 mph in some of the tight curves, which might have meant the converter was at least not frequently locked up.

One other thing I noted is that my 2000 Ex and buddies 2000 F-250 seem to shift slightly differently when not towing. My Ex seems softer, gentler, something I do not consider a durability advantage. Even my 2000 diesel shifts mushier, although it holds OD well on hills (3.73's). As second owner, maybe my buddy has an internal shift kit and doesn't know it.

Wes
...

Yes, that 3-400rpms makes a huge difference! my X was a chore to tow with when I had the 3.73`s. it always seemed like it needed a few hundred rpm more in any gear! With the 3.73`s at 65mph I couldn't hold O/D. and in 3rd at 65 it was under the rpm where it made its best power for towing. I would have to speed up to 70 to get it into the power band. with the 4.30`s it now holds O/D and it works less at 65 now too!

3.73`s are good for lower weight and less frontal area, but more is needed for heavier and taller trailers.

carringb wrote:

Wes Tausend wrote:
...

I would have probably blown the cash on a bigger tranny cooler and a Scan-Guage. I believe anything less than 3rd keeps the converter from locking up which means heat. Except for heat, that V-10 should do well on hills between 3rd and 2nd gear with 3:73's. The 4.56's will really scream in 2nd. I think OD is probably out of the question, even with 4.56's, on most mountainous hills anyway. Could be wrong.

Anxious to hear how it works out too.

Wes
...

The 4R100 behind the V10 locks up in all gears, including 1st, under heavy load.

I'm pulling 12-15,000 pounds typically and always pull in O/D, and it rarely has to downshift into 3rd. Yes, 2nd gear at 60-65 MPH is screening, and it sounds great!

Thanks for the info, Bryan. I will take your word for it on the tranny. I guess I haven't seen my 4R100's lock up under about 35 mph (both with 3.73's) and am not sure what else the parameters are. It would make sense that the trucks will reach over 35 mph in all gears if the operator is willing. I'm only pulling about 8k pounds and seldom need to rev it.

I do have a phobia about "formerly excessive" rpms. There was a time in the past when rpm limits were calculated in piston speeds (piston vs wall) and high rpms definitely meant higher piston wear. I know that the V10 is under-square, meaning the stroke is longer than the bore, and I still imagine that sustained high speed causes extra wear, especially in long stroke engines.

But somewhere along the line when I wasn't looking, piston speeds must have safely increased, because newer engines (metallurgy?) do now often run at increased rpm apparently without excessive wear. Your accumulated truck mileage is a good example of V10 durability, and it does not sound like you've babied it.

dodge_guy wrote:
I can tell you that with 4.30`s you won`t drop much out of 3rd on anything but the steepest of hills. and with the 4.56`s you may actually be able to hold 3rd on the steep hills. And to really take advantage of the new ratio, get a tuner from 5 star to recalibrate the shift strategy. Fords programming sucks, the 5star tuner really makes it tow great!

dodge guy,

Thanks for the voice of experience. With my lighter TT (8k), I only drop to 2nd once in a great while around ND with my Excursion. But it might be pretty common to hit 2nd in the SD Black Hills, or mountainous regions. It already seems like 2nd is then a bit too low, even for 3.73's, but there is no intermediate gear between it and 3rd. Since 2nd sometimes already spins the rear tires, 1st is way too low, unless one has 4x4 engaged to spread the traction.

My buddy has an extended cab 2000 F-250 and pulls a 5vr closer to 11K with 3.73's. He shifts to 2nd more often than I, even occasionally on the ND I-94 if bucking a good wind on a hill. He recently likely overheated his tranny, blew a tranny seal, and lost his torque converter in the Black Hills. I will say that he probably had a hard time maintaining over 35 mph in some of the tight curves, which might have meant the converter was at least not frequently locked up.

One other thing I noted is that my 2000 Ex and buddies 2000 F-250 seem to shift slightly differently when not towing. My Ex seems softer, gentler, something I do not consider a durability advantage. Even my 2000 diesel shifts mushier, although it holds OD well on hills (3.73's). As second owner, maybe my buddy has an internal shift kit and doesn't know it.

Wes
...

If you don't like it you could always throw some 35's on the truck. :)

If your truck was turning 2100RPM at 65MPH in OD with the 3.73 gears, it will be turning about 2600RPM with the 4.56 gears.

That's pretty close to just shifting down a full gear in the transmission, and you have to listen to that all the time now, when you're not towing. It's still going to shift and when it does, you're going to have a conniption fit, because it's really going to roar. My estimate is about 3600RPMs in direct at 65MPH.

If it was purely the shifting that bothered you, this might work out, but for most people, it's the RPMs that make them uncomfortable.