Top speeds
- Thread starter Papillon
- Start date
Justin,
Any owner with serious left seat time could have told you that.
The reason we cruise at 60~65 is fuel rate.
With the new regime will come new fuel prices. Plan to slow down.
Matt
Any owner with serious left seat time could have told you that.
The reason we cruise at 60~65 is fuel rate.
With the new regime will come new fuel prices. Plan to slow down.
Matt
I was just replying to the OP who though they didn't like over 55. Mine's perfectly happy at 70+ .
My speed really depends on where I'm going and how much of my trip is drive time. If I'm on a 2 hour quick jaunt i'll cruise at 55-60 and just enjoy the drive. If I'm going across the country it's a little more hammer down (limited vacation time lol)
Ours has stock final drive and a 403....its very happy at 65mph or 105kph and so is my pocket book because of the price of fuel here in Canada but i find myself keeping up with 4 wheelers most of the time at 70 when cruising the highway. I have had it up to 85mph without issue and it does well there but no speed limit in Canada lets you go that fast and i would hate to see the ticket for that.....lol.
I could be imagining it but there seems to be this sweet spot where speed, airflow, noise etc all meld together and these coach just seem to cruise happily along.
I could be imagining it but there seems to be this sweet spot where speed, airflow, noise etc all meld together and these coach just seem to cruise happily along.
So we are replacing the transmission; getting a new one from Applied as we speak. Is this the right time to change out the FD? And if so, is 3.55 the right ratio for our 23'? I'm still trying to fully understand this thread so bare with me!
You can change the final drive separately but now is a good opportunity if you want to reduce stress on the new tranny. 3.55 is a good all-around choice and you might as well go with limited slip while you're at it. Since you have a lighter 23' coach with a 455, you could also consider 3.21 if you won't be towing or traversing mountains regularly.
Thanks for the speedy response! What do you mean by limited slip? I am eyeing this one from Applied. I can ping Nick G from Applied, but this is what I think we are talking about.
FINAL DRIVE - GMC MOTORHOME
We are a major supplier of GMC Motor Home, RV Parts. Serving GMC MOTORHOME owners everywhere.
www.gmcrvparts.com
Yeah, that's it. You'll notice further down on the page they mention the limited slip option. Our coaches have really poor traction -- they can get stuck on wet grass. With an open (standard) differential, if one of the front wheels is slipping all power gets diverted to it and you won't move. Limited slip does just what it says, it limits the slip, ensuring that both front wheels receive some power, thus boosting overall traction.Thanks for the speedy response! What do you mean by limited slip? I am eyeing this one from Applied. I can ping Nick G from Applied, but this is what I think we are talking about.
FINAL DRIVE - GMC MOTORHOME
We are a major supplier of GMC Motor Home, RV Parts. Serving GMC MOTORHOME owners everywhere.www.gmcrvparts.com
Wow - Great thread as this year I will be taking mine through some of the Colorado Mountains. I have a feeling I will be budgeting for a new FD unit install next winter.
But the I noticed what you said Christo. "I have a 3.50 ratio, achieved by changing the chain drive sprocket between the engine and transmission"
What exactly is this option? Have not seen that mentioned before, and wondering what this alternative is that you speak of? Inquiring minds want to know.
But the I noticed what you said Christo. "I have a 3.50 ratio, achieved by changing the chain drive sprocket between the engine and transmission"
What exactly is this option? Have not seen that mentioned before, and wondering what this alternative is that you speak of? Inquiring minds want to know.
The nice thing about the higher ratio FD is that it takes some of the torque off of the transmission wear parts, including the chain drive, which iirc, is becoming in short supply. Either way, with less torque comes less wear and stretch. Making it easier on an already very tough transmission is going to make it last even longer.
A con equates to malicious intent and I assure you that's not the case. The Power Drive was developed and sold by CasPro and was later available from Manny Trovao I believe. Both vendors have contributed greatly to the GMCMH community. The Power Drive simply became obsolete once better alternatives became available. I have one on my coach, installed by a PO, that has performed well for many years.
I think he meant con as in downside, not as in you're trying to con him
I'd love to drive a coach with a higher final drive, I've had no issues with my stock FD even towing, but I guess a little more pep is always welcome!
My coach has a 3:70 with LS. I bought it from a guy in MT and he went to that ratio due to towing over the mountains. If it was my choice I‘d go to the 3:55 but I don’t mind the 3:70. In any case I’d go with the LS. It Has saved my butt more than a few times including a situation that could have been very serious.I think he meant con as in downside, not as in you're trying to con him
I'd love to drive a coach with a higher final drive, I've had no issues with my stock FD even towing, but I guess a little more pep is always welcome!
I see again mention of changing the rive chain to obtain that 3.50 ratio. Where can I buy those parts and how big a job is it?
Manny's Transmissions still lists the Power Drive on his web page. Since it requires the transmission to handle the increased torque, I would be more inclined to go with a higher ratio final drive instead.
Transmission
Rebuilt THM425 Transmission Rugged and Reliable - T he Turbo-Hydramatic 425 was an automatic transmission developed and produced by General Motors from 1966 to 1978. The THM425 was originally...
www.mannystransmission.com
Janvalen,
Changing out that chain and sprockets is not a terrible job with the transmission on a bench. The torque converter end sprocket has to press onto the shaft and there is a lot to know about the assembly. With this mod, the transmission is still running at the low speed and high torque that is very hard on it.
As a more rational change, a higher numerical final drive unloads the engine, torque converter and the transmission. If you install a higher final drive, you can also get it assembled with a Limited Slip option. When you get stuck on wet grass, you will understand why you want this option. TZEs don't like slippery.
Lastly, we do not know what your coach is. They are not all the same. If it is a later 26' and up over 11K#, then you really should consider a 3.70 gear set.
Matt
Changing out that chain and sprockets is not a terrible job with the transmission on a bench. The torque converter end sprocket has to press onto the shaft and there is a lot to know about the assembly. With this mod, the transmission is still running at the low speed and high torque that is very hard on it.
As a more rational change, a higher numerical final drive unloads the engine, torque converter and the transmission. If you install a higher final drive, you can also get it assembled with a Limited Slip option. When you get stuck on wet grass, you will understand why you want this option. TZEs don't like slippery.
Lastly, we do not know what your coach is. They are not all the same. If it is a later 26' and up over 11K#, then you really should consider a 3.70 gear set.
Matt
I did install a 3.70 on my coach, due to cost I did not go with the LSD, a lot of suggestions to get the LSD but also was told the majority do not have the LSD and are doing fine. I suppose when I get stuck the 1st time I will find the extra cash and have an LSD installed but I have so much work to do it is not on the To Do list, LOL
As far as changing it yourself, you do need mechanical ability and making a jig for your jack to hold the FD really helps.
As far as changing it yourself, you do need mechanical ability and making a jig for your jack to hold the FD really helps.
