trany? help

[dbloyd]

iam a new member, and i have some ?
my trany has slipped and only works in low and reverse.
check engine light is on. man at autozone checked for codes.
i have 2 codes p0700 and p0847. what can this mean? thanks, daniel.
my truck is 02 gmc lb7 and allison, with 144,000 miles with a 70-125
vanakan box, afe,4inch exuast.

 

[JMDuramaxLB7]

The po700 code is a generic trans code, basicly the tcm is telling the ecm that there are codes in the tranny, need a better code reader to get the actual tranny code. Go to a reputable shop and have them read the codes with a good scanner or if you have a buddy with EFI live, that can read them also.

 

[Mike L.]

Pull the pan and check for clutch material in the pan. Cut both filter open and see what's inside them.
P0847 is a pressure switch manifold code for D shift valve. Could mean a bad pressure switch manifold, bad solenoid, crap in the pressure switch, dirty spin on filter, or a toasted trans. Van Aken's are not known to be kind to Allisons. They cause a lot of tie ups.

 

[dbloyd]

this all happened last sat. when i was towing a small tractor.
at about 35 mph coming through town. the engine rpm suddenly went
up and it stopped pulling then it went down into low. i limped it
on home at 15 mph. the trany temp was 190 degrees. i tried to drive
the truck this morning and all was ok. when the trany temp came up to
160 it did it again. any one know of a good trany shop in my area that knows allisons? i live near selmer tn.

 

[dbloyd]

trany help update

i have taken the truck to the shop.
they replaced the manifold pressure switches changed the
filters and fluid. they said the trany was clean inside. no
sediment or clutch material. they called today and said after
a test drive that it shifted funny with like hicup between shift
and when the trany temp comes up after about 6 miles it goes
back into limp mode again but they are no longer getting those
codes that it was throwing on those switches. they are going to
pull the trany today and go into it. do you have any ideas what else
could be wrong? thanks daniel.

 

[dbloyd]

update. i got my truck back from the shop. every things good again.
they said the final drive clutches were worn and the piston had a crack
in it. they did a complete rebuild while it was already apart. the shop
said it happened because i was towing without using the tow/haul on.
does using this feature keep the truck out of overdrive or just what does it do?
thanks for your advice.

 

[JustinD]

Take the Van Aken out.

 

[Mike L.]

update. i got my truck back from the shop. every things good again.
they said the final drive clutches were worn and the piston had a crack
in it. they did a complete rebuild while it was already apart. the shop
said it happened because i was towing without using the tow/haul on.
does using this feature keep the truck out of overdrive or just what does it do?
thanks for your advice.

Your shop is wet behind the ears.

 

[Chevy1925]

Your shop is wet behind the ears.

Yup and milkin the green stuff out of him

 

[JustinD]

Your shop is wet behind the ears.

Yup and milkin the green stuff out of him

Seems like that is the case more than not. Thats why you need to leave the trans builds to the "Trans guys"

 

[dbloyd]

this was the only shop in my area that i could find
that had any experience the the allison. the rebuild
was expensive, like $ 2700. i already removed the
vanaken box, for iam not willing to take any more
chances with it. they gave me a 12 month 12000
mile warenty with it. i have been driving it for 2 weeks
now and its doing well. iam happy with the outcome.
i thank you all for your advice.

 

[duratothemax]

I would love to see pictures of these "worn final drive clutches" and cracked piston