700R4 that only mildly backs up at 1200 rpm

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Gilmore

Full Access Member
Joined
May 1, 2019
Posts
66
Reaction score
37
Location
Eureka
First Name
Christopher
Truck Year
1984
Truck Model
K10
Engine Size
6.2L Diesel
Ok I have a 1984 chevy K10 w/350 HO and a TCI Maximizer 700r4. The issue I have is that this is a new transmission and it goes forward like a freight train but backing up is a problem. When I shift into drive with my foot off the brake the truck moves. When I shift the truck in reverse however nothing until I hit 1200 RPMs and even then it’s anemic at best. Any help or good questions are appreciated!

Link to Trans: https://www.jegs.com/i/TCI/890/3714...=Transactional&utm_content=Order+Confirmation
 

Tank6x2

Supporting Member
Supporting Member
Joined
Mar 27, 2017
Posts
814
Reaction score
659
Location
Edmonton Alberta Canada
First Name
Kurt
Truck Year
79/86
Truck Model
C30
Engine Size
350, TH400.4:10 gears 2WD
Sounds like a plugged flow port, drop filter and check valve ports - may be assembled with debris.
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,338
Reaction score
3,571
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
If it’s a new transmission, I wouldn’t do anything until you talk to TCI. Make absolutely sure you have followed their installation instructions to the letter before calling them.

I’d be curious to know what they say.
 

Gilmore

Full Access Member
Joined
May 1, 2019
Posts
66
Reaction score
37
Location
Eureka
First Name
Christopher
Truck Year
1984
Truck Model
K10
Engine Size
6.2L Diesel
TCI just tells me I have too much fluid, the trans only take 6qts. I emptied the trans and put back in exactly 6 qts and the same behavior.
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,338
Reaction score
3,571
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
Find a gauge that reads to 300 psi, put it in the line pressure tap about the manual linkage. See what the pressure is in reverse.

It isn’t normal to need to rev the engine to back up.

Have you driven it yet? If so, get it up to 30mph, put the shifter in 1st, see if it has engine braking. If not, the low/reverse clutch pack is suspect. If it does, the reverse input clutch is the problem.
 

Gilmore

Full Access Member
Joined
May 1, 2019
Posts
66
Reaction score
37
Location
Eureka
First Name
Christopher
Truck Year
1984
Truck Model
K10
Engine Size
6.2L Diesel
Apparently I need to flush the trans and torque converter because you can’t use full synthetic fluid in a TH350, 400 or 700R4 it needs to be petroleum based Dex3.
 

82sbshortbed

Fuckemall!!
Joined
Mar 1, 2018
Posts
14,648
Reaction score
48,568
Location
SE Texas
First Name
Doug
Truck Year
1982, 1984
Truck Model
1500 shortbed, 1500 longbed
Engine Size
454, 305
Yes I use valvoline max life in red bottle at Walmart for cheaper price.
 

Gilmore

Full Access Member
Joined
May 1, 2019
Posts
66
Reaction score
37
Location
Eureka
First Name
Christopher
Truck Year
1984
Truck Model
K10
Engine Size
6.2L Diesel
Yeah I did too but that is full synthetic and apparently is too thin once the trans is warm to allow the reverse clutch to engage.
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,135
Reaction score
4,984
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
Yes I use valvoline max life in red bottle at Walmart for cheaper price.
Thats a full synthetic Dex VI equivalent. It meets the Dex III spec also, but is slightly thinner than the standard blue bottle Valvoline ATF
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,338
Reaction score
3,571
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
There is a bleed hole in the reverse input clutch piston, from the factory the hole is a little too big. TransGo include a tiny freeze plug with a very small orifice that make the bleed hole smaller. You can buy the freeze plugs from TransStar and other venders.

Put a pressure gauge on it. TCI lists line pressure specs for each model transmission. Assuming the pump is good, the transmission was built correctly, and the cable is installed and adjusted properly, synthetic fluid isn’t your problem. If TCI is telling you otherwise, it sounds to me like they are backpedaling.
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,338
Reaction score
3,571
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds

Gilmore

Full Access Member
Joined
May 1, 2019
Posts
66
Reaction score
37
Location
Eureka
First Name
Christopher
Truck Year
1984
Truck Model
K10
Engine Size
6.2L Diesel
There is a bleed hole in the reverse input clutch piston, from the factory the hole is a little too big. TransGo include a tiny freeze plug with a very small orifice that make the bleed hole smaller. You can buy the freeze plugs from TransStar and other venders.

Put a pressure gauge on it. TCI lists line pressure specs for each model transmission. Assuming the pump is good, the transmission was built correctly, and the cable is installed and adjusted properly, synthetic fluid isn’t your problem. If TCI is telling you otherwise, it sounds to me like they are backpedaling.
Well it’s going to cost me $200 to get the transmission and torque converter flushed so I hope your wrong and this works. ;)
 

Gilmore

Full Access Member
Joined
May 1, 2019
Posts
66
Reaction score
37
Location
Eureka
First Name
Christopher
Truck Year
1984
Truck Model
K10
Engine Size
6.2L Diesel
Well it’s going to cost me $200 to get the transmission and torque converter flushed so I hope your wrong and this works. ;)
Well you weren’t wrong, the flush didn’t work now I’m talking to the warranty manager.
 

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
10,019
Reaction score
14,166
Location
Right where I am
First Name
Bagoomba
Truck Year
1981, 1965
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
Engine Size
Carb'ed Vortec 350; 1972 L48 350
.
 

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
10,019
Reaction score
14,166
Location
Right where I am
First Name
Bagoomba
Truck Year
1981, 1965
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
Engine Size
Carb'ed Vortec 350; 1972 L48 350
Well it’s going to cost me $200 to get the transmission and torque converter flushed so I hope your wrong and this works. ;)

Well you weren’t wrong, the flush didn’t work now I’m talking to the warranty manager.
Are you arguing with yourself?...lol...
 
  • Like
Reactions: WFO

Latest posts

Forum statistics

Threads
41,859
Posts
903,668
Members
33,372
Latest member
83elcowes
Top