Braking in the Rain

[Gadget Man]

I've yet to drive my Providence in the rain. After all, I am in California...

All of the material that accompanied my MH says NOT to use the Jake Brake when the roadway is wet. Would I be correct in assuming that besides slowing way down, I should use mainly the transmission to slow the rig down when descending a grade in the rain?

[Gadget Man]

I've yet to drive my Providence in the rain. After all, I am in California...

All of the material that accompanied my MH says NOT to use the Jake Brake when the roadway is wet. Would I be correct in assuming that besides slowing way down, I should use mainly the transmission to slow the rig down when descending a grade in the rain?

[Lug_Nut]

No, actually you should use more service braking than transmission as the service brakes apply on all wheels whereas your engine brake is only on the drive axle. Usually some engine braking can be used during travel on rain soaked roads, but be very careful when it first starts raining. This is when the road surface is most prone to be slippery due to oil deposits that have gathered.

[rebelsbeach]

Peter is as usual, 100 percent correct...

The most DANGEROUS time to drive in the rain is when it has first started "sprinkling" as the light coating of water brings the oil deposits to the top and causes a very slippery condition.

It is also recommended in many professional driving schools to do as Peter has recommended and use the SERVICE BRAKES with the absence of the Jacobs Brake, to slow the vehicle.

[Gadget Man]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Lug_Nut:
No, actually you should use more service braking than transmission </div></BLOCKQUOTE>
But I would still need to use some transmission braking though, correct?

[rebelsbeach]

Your Allison will follow suit, for the most part, with what you do with your feet.
In an extreme descent it may be necessary to use the tranny, but if you're aware of your surroundings and watch the road signs and so forth, you should be fine....

[ajbjrvers]

To; Craig P.

Re; using jake brake on wet roads.

When I was at the Spartan factory last year because of a front end problem, I was told the following.

Use your service brakes more often because the noise you heard was corrosion had built up on back plates and caused the shoes to hang up and then release with a BANG. They also said it's alot cheaper to redo brakes then to overhaul tranny. Downshifting manually can cause rear end to slide as well as jake brake on wet roads.

Hope this info helps== AIME== AJBJRVERS==

[GaryKD]

Hi Craig,
No exhaust, engine or jake brake when the pavement is any kind of slippery. If the environment is wet/slippery road surface, consider manually down shifting the transmission at the top of the hill into the gear you went up the hill in. To be conservetive, one gear lower. Start down the hill and you should have no problems.

There are many posts on this and other forums with links to bus and truck (professional driver!) accidents that were caused by using the above mentioned (exhaust, engine or jake brake) breaking method on slippery pavement. Going down a hill a little slower than you want is only going to require some patience.

[rebelsbeach]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by GaryKD:
There are many posts on this and other forums with links to bus and truck (professional driver!) accidents that were caused by using the above mentioned braking method. Going down a hill a little slower than you want is only going to require some patience. </div></BLOCKQUOTE>

Which method are you referring to Gary?

[Roland]

Craig,
Downshifting the transmission to a lower gear only works on a gas engine. If you are not using a "Jake Brake" (engine brake) or an exhaust brake (PAC Brake style)there is insufficent back pressure, with a diesel engine, to slow you down in any meaningful distance. As others have said -- Out West where it seldom rains the first rains tend to lift the oil that has been deposited on the road and cause a slippery condition. The same for heavy rain causing standing water on the road surface. One problem with engine & exhaust brakes is when the Allison trans downshifts there is a momentary increase of back pressure on the drive train and if you are on a slippery surface it could cause the rear drive wheels to brake loose on the road surface. When it rains slow down and drive with caution. If you need the extra braking capability of an engine or exhaust brake evaluate the road conditions first.

[rebelsbeach]

Huh??

Roland, you may want to check out page 30 of the Allison Motorhome Transmission Operator's Manual where it accurate describes selecting the next lower gear BEFORE reaching the downhill...


Allison MH Tranny Manual

[JerryKelly]

A good rule of thumb is to use the same gear you did to climb the hill. Don't be fooled by the truck drivers using their jake in the rain. They can disengage it faster than you can since they have a clutch. Patience will be you best braking system.

[Roland]

Good afternoon Bob,

Thank you for providing the link to the Allison Manual OM3349EM. When my copy printed page 30 covered the use of the "Hydraulic Retarder"�. But I believe that I found your point on page 29.

"...When the vehicle is heavily loaded, or the grade is steep, it may be desirable, to preselect lower range before reaching the grade...."�

I have no disagreement with the above statement as it stands. However, the context that I was addressing was:

Subject: "Braking in the rain"�

Comment: "... No exhaust, engine or jake brake when the pavement is any kind of slippery. If the environment is wet/slippery road surface, consider manually down shifting the transmission at the top of the hill into the gear you went up the hill in. To be conservative, one gear lower...."�

I trust that we can agree that gas engines have a compression back pressure when the throttle position is zero. Diesel engines do not to any appreciable extent. If they did there would be no market for engine or exhaust brakes for diesels.

Doing 60 mph on the flat, in a diesel RV, take your foot off the throttle and see how far you will coast. Doing 55 mph at the top of a 6% grade and manually select 4th range, with the engine/exhaust brake "off"�. You will pickup speed and when your engine rpm's exceed the engine governed speed, the Allison transmission will upshift to the next higher range to prevent engine damage.

My point is that the "Never go down a mountain grade in a gear higher than the lowest gear it took you to go up"� is far more applicable to the gas driver than it will be to the diesel driver. The gas driver has the benefit of both engine compression (during the entire descent) and service brakes. The diesel driver is essentially using only his service brakes; unless he is using other retarding devices.

Allison – p29 also says "... To avoid loss of control, use a combination of downshifting, braking, and other retarding devices...."� The paragraphs, the above statements are derived from, do not address inclement weather operation. This implies that the excerpts are based on the ability to use both service brakes and "other retarding devices"�.

I believe Peter "spoke well"� when he wrote "...Usually some engine braking can be used , but be very careful when it first starts raining...."�

Have a nice day,

[GaryKD]

Bob,
I have edited my post. This should answer your question.